diff --git a/toolchain/check/call.cpp b/toolchain/check/call.cpp
index 9b8e82572f15..2146045d5548 100644
--- a/toolchain/check/call.cpp
+++ b/toolchain/check/call.cpp
@@ -263,11 +263,13 @@ auto PerformCallToFunction(Context& context, SemIR::LocId loc_id,
   switch (callee.special_function_kind) {
     case SemIR::Function::SpecialFunctionKind::Thunk: {
       // If we're about to form a direct call to a thunk, inline it.
-      LoadImportRef(context, callee.thunk_decl_id());
+      auto callee_inst_id =
+          context.sem_ir().thunks().Get(callee.thunk_id()).callee_id;
+      LoadImportRef(context, callee_inst_id);
 
       // Name the thunk target within the enclosing scope of the thunk.
       auto thunk_ref_id =
-          BuildNameRef(context, loc_id, callee.name_id, callee.thunk_decl_id(),
+          BuildNameRef(context, loc_id, callee.name_id, callee_inst_id,
                        callee_function.enclosing_specific_id);
 
       auto param_pattern_ids =
diff --git a/toolchain/check/import_ref.cpp b/toolchain/check/import_ref.cpp
index 0fbbb0f5845a..c9d13dfaf4ab 100644
--- a/toolchain/check/import_ref.cpp
+++ b/toolchain/check/import_ref.cpp
@@ -158,6 +158,9 @@ class ImportContext {
 
   // Returns the file we are importing from.
   auto import_ir() -> const SemIR::File& { return import_ir_; }
+  auto import_thunks() -> const SemIR::ThunkStore& {
+    return import_ir().thunks();
+  }
 
   // Accessors into value stores of the file we are importing from.
   auto import_associated_constants() -> const SemIR::AssociatedConstantStore& {
@@ -2323,6 +2326,25 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
       GetLocalConstantInstId(resolver, import_function.self_param_id);
   auto return_pattern_id =
       GetLocalConstantInstId(resolver, import_function.return_pattern_id);
+
+  const SemIR::ThunkInfo* import_thunk_info = nullptr;
+  if (import_function.special_function_kind ==
+          SemIR::Function::SpecialFunctionKind::Thunk &&
+      import_function.thunk_id().has_value()) {
+    import_thunk_info =
+        &resolver.import_thunks().Get(import_function.thunk_id());
+  }
+  auto thunk_signature_inst_id =
+      import_thunk_info
+          ? GetLocalConstantInstId(resolver,
+                                   resolver.import_functions()
+                                       .Get(import_thunk_info->signature_id)
+                                       .first_decl_id())
+          : SemIR::InstId::None;
+  auto thunk_specific_data = GetLocalSpecificData(
+      resolver, import_thunk_info ? import_thunk_info->specific_id
+                                  : SemIR::SpecificId::None);
+
   auto& new_function = resolver.local_functions().Get(function_id);
   if (resolver.HasNewWork()) {
     return ResolveResult::Retry(function_const_id,
@@ -2369,11 +2391,23 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
       break;
     }
     case SemIR::Function::SpecialFunctionKind::Thunk: {
+      auto thunk_signature_type_id =
+          resolver.local_insts().Get(thunk_signature_inst_id).type_id();
       auto entity_name_id = resolver.local_entity_names().AddCanonical(
           {.name_id = new_function.name_id,
            .parent_scope_id = new_function.parent_scope_id});
-      new_function.SetThunk(AddImportRef(
-          resolver, import_function.thunk_decl_id(), entity_name_id));
+      SemIR::ThunkInfo local_thunk_info = {
+          .callee_id = AddImportRef(resolver, import_thunk_info->callee_id,
+                                    entity_name_id),
+          .signature_id =
+              resolver.local_types()
+                  .GetAs<SemIR::FunctionType>(thunk_signature_type_id)
+                  .function_id};
+      if (import_thunk_info->specific_id.has_value()) {
+        local_thunk_info.specific_id = GetOrAddLocalSpecific(
+            resolver, import_thunk_info->specific_id, thunk_specific_data);
+      }
+      new_function.SetThunk(resolver.local_ir().thunks().Add(local_thunk_info));
       break;
     }
     case SemIR::Function::SpecialFunctionKind::HasCppThunk: {
@@ -2487,7 +2521,7 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
       resolver.import_functions().Get(inst.function_id).first_decl_id());
 
   auto specific_data = GetLocalSpecificData(resolver, inst.specific_id);
-  if (resolver.HasNewWork()) {
+  if (resolver.HasNewWork() || !fn_val_id.has_value()) {
     return ResolveResult::Retry();
   }
   auto fn_type_id = resolver.local_insts().Get(fn_val_id).type_id();
@@ -4116,11 +4150,9 @@ static auto TryResolveInstCanonical(ImportRefResolver& resolver,
   CARBON_CHECK(!const_id.has_value());
 
   auto inst_constant_id = resolver.import_constant_values().Get(inst_id);
-  if (!inst_constant_id.is_constant()) {
+  if (!inst_constant_id.has_value() || !inst_constant_id.is_constant()) {
     // TODO: Import of non-constant BindNames happens when importing `let`
     // declarations.
-    CARBON_CHECK(resolver.import_insts().Is<SemIR::AnyBinding>(inst_id),
-                 "TryResolveInst on non-constant instruction {0}", inst_id);
     return ResolveResult::Done(SemIR::ConstantId::NotConstant);
   }
 
diff --git a/toolchain/check/testdata/for/actual.carbon b/toolchain/check/testdata/for/actual.carbon
index 3cad68f56a00..8698a505d5f0 100644
--- a/toolchain/check/testdata/for/actual.carbon
+++ b/toolchain/check/testdata/for/actual.carbon
@@ -150,9 +150,9 @@ fn Read(y:! Core.IntLiteral()) {
 // CHECK:STDOUT:   %Int.as.OrderedWith.impl.Less.type.da0: type = fn_type @Int.as.OrderedWith.impl.Less.1, @Int.as.OrderedWith.impl.b74(%N, %N) [symbolic]
 // CHECK:STDOUT:   %Int.as.OrderedWith.impl.Less.2b7: %Int.as.OrderedWith.impl.Less.type.da0 = struct_value () [symbolic]
 // CHECK:STDOUT:   %.851: require_specific_def_type = require_specific_def @Int.as.OrderedWith.impl.b74(%N, %N) [symbolic]
-// CHECK:STDOUT:   %OrderedWith.facet: %OrderedWith.type.e44 = facet_value %Int.fc6021.1, (%OrderedWith.impl_witness.e5b) [symbolic]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.b0e: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Int.fc6021.1, %OrderedWith.facet) [symbolic]
-// CHECK:STDOUT:   %.a4b: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.b0e, %OrderedWith.facet [symbolic]
+// CHECK:STDOUT:   %OrderedWith.facet.76c: %OrderedWith.type.e44 = facet_value %Int.fc6021.1, (%OrderedWith.impl_witness.e5b) [symbolic]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.b0e: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Int.fc6021.1, %OrderedWith.facet.76c) [symbolic]
+// CHECK:STDOUT:   %.a4b: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.b0e, %OrderedWith.facet.76c [symbolic]
 // CHECK:STDOUT:   %Int.as.OrderedWith.impl.Less.specific_fn.5fb: <specific function> = specific_function %Int.as.OrderedWith.impl.Less.2b7, @Int.as.OrderedWith.impl.Less.1(%N, %N) [symbolic]
 // CHECK:STDOUT:   %Inc.type: type = facet_type <@Inc> [concrete]
 // CHECK:STDOUT:   %Inc.lookup_impl_witness: <witness> = lookup_impl_witness %Int.fc6021.1, @Inc [symbolic]
@@ -594,7 +594,7 @@ fn Read(y:! Core.IntLiteral()) {
 // CHECK:STDOUT:   %assoc0: @IntRange.as.Iterate.impl.Next.%OrderedWith.assoc_type (%OrderedWith.assoc_type.215) = assoc_entity element0, imports.%Core.import_ref.255 [symbolic = %assoc0 (constants.%assoc0.15c)]
 // CHECK:STDOUT:   %.loc13_17.2: require_specific_def_type = require_specific_def @Int.as.OrderedWith.impl.b74(%N, %N) [symbolic = %.loc13_17.2 (constants.%.851)]
 // CHECK:STDOUT:   %OrderedWith.impl_witness: <witness> = impl_witness imports.%OrderedWith.impl_witness_table.324, @Int.as.OrderedWith.impl.b74(%N, %N) [symbolic = %OrderedWith.impl_witness (constants.%OrderedWith.impl_witness.e5b)]
-// CHECK:STDOUT:   %OrderedWith.facet: @IntRange.as.Iterate.impl.Next.%OrderedWith.type.loc13_17.2 (%OrderedWith.type.e44) = facet_value %Int.loc11_43.1, (%OrderedWith.impl_witness) [symbolic = %OrderedWith.facet (constants.%OrderedWith.facet)]
+// CHECK:STDOUT:   %OrderedWith.facet: @IntRange.as.Iterate.impl.Next.%OrderedWith.type.loc13_17.2 (%OrderedWith.type.e44) = facet_value %Int.loc11_43.1, (%OrderedWith.impl_witness) [symbolic = %OrderedWith.facet (constants.%OrderedWith.facet.76c)]
 // CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Int.loc11_43.1, %OrderedWith.facet) [symbolic = %OrderedWith.WithSelf.Less.type (constants.%OrderedWith.WithSelf.Less.type.b0e)]
 // CHECK:STDOUT:   %.loc13_17.3: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type, %OrderedWith.facet [symbolic = %.loc13_17.3 (constants.%.a4b)]
 // CHECK:STDOUT:   %Int.as.OrderedWith.impl.Less.type: type = fn_type @Int.as.OrderedWith.impl.Less.1, @Int.as.OrderedWith.impl.b74(%N, %N) [symbolic = %Int.as.OrderedWith.impl.Less.type (constants.%Int.as.OrderedWith.impl.Less.type.da0)]
diff --git a/toolchain/check/testdata/impl/fail_call_invalid.carbon b/toolchain/check/testdata/impl/fail_call_invalid.carbon
index 792cb99d6659..b494efd16855 100644
--- a/toolchain/check/testdata/impl/fail_call_invalid.carbon
+++ b/toolchain/check/testdata/impl/fail_call_invalid.carbon
@@ -152,7 +152,7 @@ fn InstanceCall(n: i32) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @i32.as.Simple.impl.G.loc24_27.1(%self.param: <error>);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @i32.as.Simple.impl.G.loc24_27.2(%self.param: %i32) [thunk @i32.as.Simple.impl.%i32.as.Simple.impl.G.decl.loc24_27.1] {
+// CHECK:STDOUT: fn @i32.as.Simple.impl.G.loc24_27.2(%self.param: %i32) [thunk @i32.as.Simple.impl.%i32.as.Simple.impl.G.decl.loc24_27.1 for @Simple.WithSelf.%Simple.WithSelf.G.decl, @Simple.WithSelf.G(constants.%Simple.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %G.ref: %i32.as.Simple.impl.G.type.32ad7a.1 = name_ref G, @i32.as.Simple.impl.%i32.as.Simple.impl.G.decl.loc24_27.1 [concrete = constants.%i32.as.Simple.impl.G.4f6260.1]
 // CHECK:STDOUT:   %i32.as.Simple.impl.G.bound: <bound method> = bound_method %self.param, %G.ref
diff --git a/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon b/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
index 46175ee08358..43fedd3c57ce 100644
--- a/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
+++ b/toolchain/check/testdata/impl/fail_impl_bad_assoc_fn.carbon
@@ -1208,7 +1208,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FExtraParam.as.I.impl.F.loc69_18.1(%b.param: bool);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FExtraParam.as.I.impl.F.loc69_18.2() [thunk @FExtraParam.as.I.impl.%FExtraParam.as.I.impl.F.decl.loc69_18.1] {
+// CHECK:STDOUT: fn @FExtraParam.as.I.impl.F.loc69_18.2() [thunk @FExtraParam.as.I.impl.%FExtraParam.as.I.impl.F.decl.loc69_18.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet.b53)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FExtraParam.as.I.impl.F.type.531438.1 = name_ref F, @FExtraParam.as.I.impl.%FExtraParam.as.I.impl.F.decl.loc69_18.1 [concrete = constants.%FExtraParam.as.I.impl.F.33e1fe.1]
 // CHECK:STDOUT:   return
@@ -1216,7 +1216,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FExtraImplicitParam.as.I.impl.F.loc85_23.1(%self.param: %FExtraImplicitParam);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FExtraImplicitParam.as.I.impl.F.loc85_23.2() [thunk @FExtraImplicitParam.as.I.impl.%FExtraImplicitParam.as.I.impl.F.decl.loc85_23.1] {
+// CHECK:STDOUT: fn @FExtraImplicitParam.as.I.impl.F.loc85_23.2() [thunk @FExtraImplicitParam.as.I.impl.%FExtraImplicitParam.as.I.impl.F.decl.loc85_23.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet.5a5)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FExtraImplicitParam.as.I.impl.F.type.9dd145.1 = name_ref F, @FExtraImplicitParam.as.I.impl.%FExtraImplicitParam.as.I.impl.F.decl.loc85_23.1 [concrete = constants.%FExtraImplicitParam.as.I.impl.F.99eae8.1]
 // CHECK:STDOUT:   %FExtraImplicitParam.as.I.impl.F.call: init %empty_tuple.type = call %F.ref(<error>)
@@ -1231,7 +1231,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FMissingParam.as.J.impl.F.loc117_31.1(%self.param: bool) -> out %return.param: bool;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FMissingParam.as.J.impl.F.loc117_31.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingParam.as.J.impl.%FMissingParam.as.J.impl.F.decl.loc117_31.1] {
+// CHECK:STDOUT: fn @FMissingParam.as.J.impl.F.loc117_31.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingParam.as.J.impl.%FMissingParam.as.J.impl.F.decl.loc117_31.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.567)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FMissingParam.as.J.impl.F.type.0f71d8.1 = name_ref F, @FMissingParam.as.J.impl.%FMissingParam.as.J.impl.F.decl.loc117_31.1 [concrete = constants.%FMissingParam.as.J.impl.F.7540f6.1]
 // CHECK:STDOUT:   %FMissingParam.as.J.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1240,7 +1240,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FMissingImplicitParam.as.J.impl.F.loc130_26.1(%b.param: bool) -> out %return.param: bool;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FMissingImplicitParam.as.J.impl.F.loc130_26.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingImplicitParam.as.J.impl.%FMissingImplicitParam.as.J.impl.F.decl.loc130_26.1] {
+// CHECK:STDOUT: fn @FMissingImplicitParam.as.J.impl.F.loc130_26.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingImplicitParam.as.J.impl.%FMissingImplicitParam.as.J.impl.F.decl.loc130_26.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.266)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FMissingImplicitParam.as.J.impl.F.type.80a56b.1 = name_ref F, @FMissingImplicitParam.as.J.impl.%FMissingImplicitParam.as.J.impl.F.decl.loc130_26.1 [concrete = constants.%FMissingImplicitParam.as.J.impl.F.c6a0b7.1]
 // CHECK:STDOUT:   %FMissingImplicitParam.as.J.impl.F.call: init bool = call %F.ref(%b.param)
@@ -1249,7 +1249,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FMissingReturnType.as.J.impl.F.loc152_30.1(%self.param: bool, %b.param: bool);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FMissingReturnType.as.J.impl.F.loc152_30.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingReturnType.as.J.impl.%FMissingReturnType.as.J.impl.F.decl.loc152_30.1] {
+// CHECK:STDOUT: fn @FMissingReturnType.as.J.impl.F.loc152_30.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FMissingReturnType.as.J.impl.%FMissingReturnType.as.J.impl.F.decl.loc152_30.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.a9e)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FMissingReturnType.as.J.impl.F.type.ce0d21.1 = name_ref F, @FMissingReturnType.as.J.impl.%FMissingReturnType.as.J.impl.F.decl.loc152_30.1 [concrete = constants.%FMissingReturnType.as.J.impl.F.5b613a.1]
 // CHECK:STDOUT:   %FMissingReturnType.as.J.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1260,7 +1260,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FDifferentParamType.as.J.impl.F.loc171_38.1(%self.param: bool, %b.param: %FDifferentParamType) -> out %return.param: bool;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FDifferentParamType.as.J.impl.F.loc171_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentParamType.as.J.impl.%FDifferentParamType.as.J.impl.F.decl.loc171_38.1] {
+// CHECK:STDOUT: fn @FDifferentParamType.as.J.impl.F.loc171_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentParamType.as.J.impl.%FDifferentParamType.as.J.impl.F.decl.loc171_38.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.bd2)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FDifferentParamType.as.J.impl.F.type.10926d.1 = name_ref F, @FDifferentParamType.as.J.impl.%FDifferentParamType.as.J.impl.F.decl.loc171_38.1 [concrete = constants.%FDifferentParamType.as.J.impl.F.f1245a.1]
 // CHECK:STDOUT:   %FDifferentParamType.as.J.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1271,7 +1271,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FDifferentImplicitParamType.as.J.impl.F.loc184_38.1(%self.param: %FDifferentImplicitParamType, %b.param: bool) -> out %return.param: bool;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FDifferentImplicitParamType.as.J.impl.F.loc184_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentImplicitParamType.as.J.impl.%FDifferentImplicitParamType.as.J.impl.F.decl.loc184_38.1] {
+// CHECK:STDOUT: fn @FDifferentImplicitParamType.as.J.impl.F.loc184_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentImplicitParamType.as.J.impl.%FDifferentImplicitParamType.as.J.impl.F.decl.loc184_38.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.030)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FDifferentImplicitParamType.as.J.impl.F.type.955391.1 = name_ref F, @FDifferentImplicitParamType.as.J.impl.%FDifferentImplicitParamType.as.J.impl.F.decl.loc184_38.1 [concrete = constants.%FDifferentImplicitParamType.as.J.impl.F.a9ece4.1]
 // CHECK:STDOUT:   %FDifferentImplicitParamType.as.J.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1282,7 +1282,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @FDifferentReturnType.as.J.impl.F.loc200_38.1(%self.param: bool, %b.param: bool) -> out %return.param: %FDifferentReturnType;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @FDifferentReturnType.as.J.impl.F.loc200_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentReturnType.as.J.impl.%FDifferentReturnType.as.J.impl.F.decl.loc200_38.1] {
+// CHECK:STDOUT: fn @FDifferentReturnType.as.J.impl.F.loc200_38.2(%self.param: bool, %b.param: bool) -> out %return.param: bool [thunk @FDifferentReturnType.as.J.impl.%FDifferentReturnType.as.J.impl.F.decl.loc200_38.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet.4a1)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %FDifferentReturnType.as.J.impl.F.type.7bcb67.1 = name_ref F, @FDifferentReturnType.as.J.impl.%FDifferentReturnType.as.J.impl.F.decl.loc200_38.1 [concrete = constants.%FDifferentReturnType.as.J.impl.F.a709b1.1]
 // CHECK:STDOUT:   %FDifferentReturnType.as.J.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1309,7 +1309,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @SelfNestedBadParam.as.SelfNested.impl.F.loc223_87.1(%x.param: %tuple.type.70f) -> out %return.param: %array_type.388;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @SelfNestedBadParam.as.SelfNested.impl.F.loc223_87.2(%x.param: %tuple.type.7ea) -> out %return.param: %array_type.388 [thunk @SelfNestedBadParam.as.SelfNested.impl.%SelfNestedBadParam.as.SelfNested.impl.F.decl.loc223_87.1] {
+// CHECK:STDOUT: fn @SelfNestedBadParam.as.SelfNested.impl.F.loc223_87.2(%x.param: %tuple.type.7ea) -> out %return.param: %array_type.388 [thunk @SelfNestedBadParam.as.SelfNested.impl.%SelfNestedBadParam.as.SelfNested.impl.F.decl.loc223_87.1 for @SelfNested.WithSelf.%SelfNested.WithSelf.F.decl, @SelfNested.WithSelf.F(constants.%SelfNested.facet.b9f)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %SelfNestedBadParam.as.SelfNested.impl.F.type.789632.1 = name_ref F, @SelfNestedBadParam.as.SelfNested.impl.%SelfNestedBadParam.as.SelfNested.impl.F.decl.loc223_87.1 [concrete = constants.%SelfNestedBadParam.as.SelfNested.impl.F.6e1661.1]
 // CHECK:STDOUT:   %.loc211_57: ref %array_type.388 = splice_block %return.param {}
@@ -1323,7 +1323,7 @@ class SelfNestedBadReturnType {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @SelfNestedBadReturnType.as.SelfNested.impl.F.loc239_112.1(%x.param: %tuple.type.064) -> out %return.param: %array_type.388;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @SelfNestedBadReturnType.as.SelfNested.impl.F.loc239_112.2(%x.param: %tuple.type.064) -> out %return.param: %array_type.31b [thunk @SelfNestedBadReturnType.as.SelfNested.impl.%SelfNestedBadReturnType.as.SelfNested.impl.F.decl.loc239_112.1] {
+// CHECK:STDOUT: fn @SelfNestedBadReturnType.as.SelfNested.impl.F.loc239_112.2(%x.param: %tuple.type.064) -> out %return.param: %array_type.31b [thunk @SelfNestedBadReturnType.as.SelfNested.impl.%SelfNestedBadReturnType.as.SelfNested.impl.F.decl.loc239_112.1 for @SelfNested.WithSelf.%SelfNested.WithSelf.F.decl, @SelfNested.WithSelf.F(constants.%SelfNested.facet.23f)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %SelfNestedBadReturnType.as.SelfNested.impl.F.type.75d128.1 = name_ref F, @SelfNestedBadReturnType.as.SelfNested.impl.%SelfNestedBadReturnType.as.SelfNested.impl.F.decl.loc239_112.1 [concrete = constants.%SelfNestedBadReturnType.as.SelfNested.impl.F.587f77.1]
 // CHECK:STDOUT:   %.loc239_112.1: ref %array_type.388 = temporary_storage
diff --git a/toolchain/check/testdata/impl/fail_self_type_mismatch.carbon b/toolchain/check/testdata/impl/fail_self_type_mismatch.carbon
index 93714669d1f5..c29f89f080cc 100644
--- a/toolchain/check/testdata/impl/fail_self_type_mismatch.carbon
+++ b/toolchain/check/testdata/impl/fail_self_type_mismatch.carbon
@@ -255,7 +255,7 @@ impl i32 as I {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @i32.as.I.impl.F.loc43_18.1(%c.param: %C.899);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @i32.as.I.impl.F.loc43_18.2(%c.param: %C.719) [thunk @i32.as.I.impl.%i32.as.I.impl.F.decl.loc43_18.1] {
+// CHECK:STDOUT: fn @i32.as.I.impl.F.loc43_18.2(%c.param: %C.719) [thunk @i32.as.I.impl.%i32.as.I.impl.F.decl.loc43_18.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet.20f)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %i32.as.I.impl.F.type.6c53e7.1 = name_ref F, @i32.as.I.impl.%i32.as.I.impl.F.decl.loc43_18.1 [concrete = constants.%i32.as.I.impl.F.7f652f.1]
 // CHECK:STDOUT:   %.loc25: %C.899 = converted %c.param, <error> [concrete = <error>]
diff --git a/toolchain/check/testdata/impl/impl_thunk.carbon b/toolchain/check/testdata/impl/impl_thunk.carbon
index b85f5d929e7c..660d53835678 100644
--- a/toolchain/check/testdata/impl/impl_thunk.carbon
+++ b/toolchain/check/testdata/impl/impl_thunk.carbon
@@ -343,12 +343,14 @@ impl () as I({}) {
 // CHECK:STDOUT: --- struct_conversion.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %empty_tuple: %empty_tuple.type = tuple_value () [concrete]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
 // CHECK:STDOUT:   %empty_struct: %empty_struct_type = struct_value () [concrete]
 // CHECK:STDOUT:   %struct_type.a.b.391: type = struct_type {.a: %empty_tuple.type, .b: %empty_struct_type} [concrete]
 // CHECK:STDOUT:   %struct_type.c.d.15a: type = struct_type {.c: %empty_tuple.type, .d: %empty_struct_type} [concrete]
+// CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @empty_tuple.type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %struct_type.b.a.40c: type = struct_type {.b: %empty_struct_type, .a: %empty_tuple.type} [concrete]
 // CHECK:STDOUT:   %pattern_type.231: type = pattern_type %struct_type.b.a.40c [concrete]
 // CHECK:STDOUT:   %struct_type.d.c.b36: type = struct_type {.d: %empty_struct_type, .c: %empty_tuple.type} [concrete]
@@ -356,6 +358,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %pattern_type.844: type = pattern_type %struct_type.d.c.b36 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.19e4b8.1: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_48.1 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.8be29b.1: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %I.facet: %I.type = facet_value %empty_tuple.type, (%I.impl_witness) [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.19e4b8.2: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_48.2 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.8be29b.2: %empty_tuple.type.as.I.impl.F.type.19e4b8.2 = struct_value () [concrete]
 // CHECK:STDOUT:   %struct: %struct_type.c.d.15a = struct_value (%empty_tuple, %empty_struct) [concrete]
@@ -403,7 +406,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_48.1(%y.param: %struct_type.b.a.40c) -> out %return.param: %struct_type.d.c.b36;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_48.2(%x.param: %struct_type.a.b.391) -> out %return.param: %struct_type.c.d.15a [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_48.1] {
+// CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_48.2(%x.param: %struct_type.a.b.391) -> out %return.param: %struct_type.c.d.15a [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_48.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = name_ref F, @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_48.1 [concrete = constants.%empty_tuple.type.as.I.impl.F.8be29b.1]
 // CHECK:STDOUT:   %.loc10_48.1: ref %struct_type.d.c.b36 = temporary_storage
@@ -442,6 +445,8 @@ impl () as I({}) {
 // CHECK:STDOUT:   %A: type = class_type @A [concrete]
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %C: type = class_type @C [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @B.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.1ab: type = pattern_type %A [concrete]
 // CHECK:STDOUT:   %ptr.643: type = ptr_type %A [concrete]
 // CHECK:STDOUT:   %pattern_type.f29: type = pattern_type %ptr.643 [concrete]
@@ -450,6 +455,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %pattern_type.506: type = pattern_type %ptr.31e [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.1: type = fn_type @B.as.X.impl.F.loc14_37.1 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.1: %B.as.X.impl.F.type.421a66.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %B, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %ptr.27c: type = ptr_type %B [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.2: type = fn_type @B.as.X.impl.F.loc14_37.2 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.2: %B.as.X.impl.F.type.421a66.2 = struct_value () [concrete]
@@ -512,7 +518,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.1(%self.param: ref %A, %other.param: %ptr.643) -> out %return.param: %ptr.31e;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1] {
+// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %B.as.X.impl.F.type.421a66.1 = name_ref F, @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 [concrete = constants.%B.as.X.impl.F.8ec460.1]
 // CHECK:STDOUT:   %B.as.X.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -538,9 +544,12 @@ impl () as I({}) {
 // CHECK:STDOUT:   %A: type = class_type @A [concrete]
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @B.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.1ab: type = pattern_type %A [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.1: type = fn_type @B.as.X.impl.F.loc13_26.1 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.1: %B.as.X.impl.F.type.421a66.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %B, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.2: type = fn_type @B.as.X.impl.F.loc13_26.2 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.2: %B.as.X.impl.F.type.421a66.2 = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -574,7 +583,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @B.as.X.impl.F.loc13_26.1(%self.param: %A, %other.param: %A);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @B.as.X.impl.F.loc13_26.2(%self.param: %B, %other.param: %B) [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc13_26.1] {
+// CHECK:STDOUT: fn @B.as.X.impl.F.loc13_26.2(%self.param: %B, %other.param: %B) [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc13_26.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %B.as.X.impl.F.type.421a66.1 = name_ref F, @B.as.X.impl.%B.as.X.impl.F.decl.loc13_26.1 [concrete = constants.%B.as.X.impl.F.8ec460.1]
 // CHECK:STDOUT:   %B.as.X.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -589,6 +598,8 @@ impl () as I({}) {
 // CHECK:STDOUT:   %A: type = class_type @A [concrete]
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %C: type = class_type @C [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @B.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.1ab: type = pattern_type %A [concrete]
 // CHECK:STDOUT:   %ptr.643: type = ptr_type %A [concrete]
 // CHECK:STDOUT:   %pattern_type.f29: type = pattern_type %ptr.643 [concrete]
@@ -597,6 +608,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %pattern_type.506: type = pattern_type %ptr.31e [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.1: type = fn_type @B.as.X.impl.F.loc14_37.1 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.1: %B.as.X.impl.F.type.421a66.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %B, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %ptr.27c: type = ptr_type %B [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.2: type = fn_type @B.as.X.impl.F.loc14_37.2 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.2: %B.as.X.impl.F.type.421a66.2 = struct_value () [concrete]
@@ -659,7 +671,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.1(%self.param: ref %A, %other.param: %ptr.643) -> out %return.param: %ptr.31e;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1] {
+// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %B.as.X.impl.F.type.421a66.1 = name_ref F, @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 [concrete = constants.%B.as.X.impl.F.8ec460.1]
 // CHECK:STDOUT:   %B.as.X.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -685,6 +697,8 @@ impl () as I({}) {
 // CHECK:STDOUT:   %A: type = class_type @A [concrete]
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %C: type = class_type @C [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @B.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.1ab: type = pattern_type %A [concrete]
 // CHECK:STDOUT:   %ptr.643: type = ptr_type %A [concrete]
 // CHECK:STDOUT:   %pattern_type.f29: type = pattern_type %ptr.643 [concrete]
@@ -693,6 +707,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %pattern_type.506: type = pattern_type %ptr.31e [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.1: type = fn_type @B.as.X.impl.F.loc14_37.1 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.1: %B.as.X.impl.F.type.421a66.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %B, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %ptr.27c: type = ptr_type %B [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.2: type = fn_type @B.as.X.impl.F.loc14_37.2 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.2: %B.as.X.impl.F.type.421a66.2 = struct_value () [concrete]
@@ -755,7 +770,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.1(%self.param: ref %A, %other.param: %ptr.643) -> out %return.param: %ptr.31e;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1] {
+// CHECK:STDOUT: fn @B.as.X.impl.F.loc14_37.2(%self.param: ref %B, %other.param: %ptr.27c) -> out %return.param: %ptr.27c [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %B.as.X.impl.F.type.421a66.1 = name_ref F, @B.as.X.impl.%B.as.X.impl.F.decl.loc14_37.1 [concrete = constants.%B.as.X.impl.F.8ec460.1]
 // CHECK:STDOUT:   %B.as.X.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -781,9 +796,12 @@ impl () as I({}) {
 // CHECK:STDOUT:   %A: type = class_type @A [concrete]
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @B.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.1ab: type = pattern_type %A [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.1: type = fn_type @B.as.X.impl.F.loc13_30.1 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.1: %B.as.X.impl.F.type.421a66.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %B, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.type.421a66.2: type = fn_type @B.as.X.impl.F.loc13_30.2 [concrete]
 // CHECK:STDOUT:   %B.as.X.impl.F.8ec460.2: %B.as.X.impl.F.type.421a66.2 = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -817,7 +835,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @B.as.X.impl.F.loc13_30.1(%self.param: %A, %other.param: ref %A);
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @B.as.X.impl.F.loc13_30.2(%self.param: %B, %other.param: ref %B) [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc13_30.1] {
+// CHECK:STDOUT: fn @B.as.X.impl.F.loc13_30.2(%self.param: %B, %other.param: ref %B) [thunk @B.as.X.impl.%B.as.X.impl.F.decl.loc13_30.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %B.as.X.impl.F.type.421a66.1 = name_ref F, @B.as.X.impl.%B.as.X.impl.F.decl.loc13_30.1 [concrete = constants.%B.as.X.impl.F.8ec460.1]
 // CHECK:STDOUT:   %B.as.X.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -834,10 +852,13 @@ impl () as I({}) {
 // CHECK:STDOUT:   %B: type = class_type @B [concrete]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %struct_type.base.5af: type = struct_type {.base: %A} [concrete]
+// CHECK:STDOUT:   %X.type: type = facet_type <@X> [concrete]
+// CHECK:STDOUT:   %X.impl_witness: <witness> = impl_witness @A.as.X.impl.%X.impl_witness_table [concrete]
 // CHECK:STDOUT:   %.7df: Core.Form = init_form %B [concrete]
 // CHECK:STDOUT:   %pattern_type.1f4: type = pattern_type %B [concrete]
 // CHECK:STDOUT:   %A.as.X.impl.F.type.170a02.1: type = fn_type @A.as.X.impl.F.loc23_14.1 [concrete]
 // CHECK:STDOUT:   %A.as.X.impl.F.e6cf46.1: %A.as.X.impl.F.type.170a02.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %X.facet: %X.type = facet_value %A, (%X.impl_witness) [concrete]
 // CHECK:STDOUT:   %A.as.X.impl.F.type.170a02.2: type = fn_type @A.as.X.impl.F.loc23_14.2 [concrete]
 // CHECK:STDOUT:   %A.as.X.impl.F.e6cf46.2: %A.as.X.impl.F.type.170a02.2 = struct_value () [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.4: type = fn_type @Destroy.Op.loc23_14.4 [concrete]
@@ -870,7 +891,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @A.as.X.impl.F.loc23_14.1() -> out %return.param: %B;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @A.as.X.impl.F.loc23_14.2() -> out %return.param: %A [thunk @A.as.X.impl.%A.as.X.impl.F.decl.loc23_14.1] {
+// CHECK:STDOUT: fn @A.as.X.impl.F.loc23_14.2() -> out %return.param: %A [thunk @A.as.X.impl.%A.as.X.impl.F.decl.loc23_14.1 for @X.WithSelf.%X.WithSelf.F.decl, @X.WithSelf.F(constants.%X.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %A.as.X.impl.F.type.170a02.1 = name_ref F, @A.as.X.impl.%A.as.X.impl.F.decl.loc23_14.1 [concrete = constants.%A.as.X.impl.F.e6cf46.1]
 // CHECK:STDOUT:   %.loc23_14.1: ref %B = temporary_storage
@@ -904,8 +925,11 @@ impl () as I({}) {
 // CHECK:STDOUT: --- generic_function.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %type: type = facet_type <type> [concrete]
 // CHECK:STDOUT:   %.Self: %type = symbolic_binding .Self [symbolic_self]
+// CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
+// CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @empty_tuple.type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %Copy.type: type = facet_type <@Copy> [concrete]
 // CHECK:STDOUT:   %pattern_type.ce2: type = pattern_type %Copy.type [concrete]
 // CHECK:STDOUT:   %U.035: %Copy.type = symbolic_binding U, 0 [symbolic]
@@ -914,6 +938,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %.435d17.2: Core.Form = init_form %U.as_type.255 [symbolic]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.19e4b8.1: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_34.1 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.8be29b.1: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %I.facet: %I.type = facet_value %empty_tuple.type, (%I.impl_witness) [concrete]
 // CHECK:STDOUT:   %T.67d: type = symbolic_binding T, 0 [symbolic]
 // CHECK:STDOUT:   %ptr.e8f: type = ptr_type %T.67d [symbolic]
 // CHECK:STDOUT:   %pattern_type.4f4: type = pattern_type %ptr.e8f [symbolic]
@@ -1024,7 +1049,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %Copy.facet.loc10_34.2: %Copy.type = facet_value %ptr, (%Copy.lookup_impl_witness) [symbolic = %Copy.facet.loc10_34.2 (constants.%Copy.facet)]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.specific_fn.loc10_34.2: <specific function> = specific_function constants.%empty_tuple.type.as.I.impl.F.8be29b.1, @empty_tuple.type.as.I.impl.F.loc10_34.1(%Copy.facet.loc10_34.2) [symbolic = %empty_tuple.type.as.I.impl.F.specific_fn.loc10_34.2 (constants.%empty_tuple.type.as.I.impl.F.specific_fn)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: @empty_tuple.type.as.I.impl.F.loc10_34.2.%ptr (%ptr.e8f)) -> out %return.param: @empty_tuple.type.as.I.impl.F.loc10_34.2.%ptr (%ptr.e8f) [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_34.1] {
+// CHECK:STDOUT:   fn(%x.param: @empty_tuple.type.as.I.impl.F.loc10_34.2.%ptr (%ptr.e8f)) -> out %return.param: @empty_tuple.type.as.I.impl.F.loc10_34.2.%ptr (%ptr.e8f) [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_34.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet, constants.%T.67d)] {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %F.ref: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = name_ref F, @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_34.1 [concrete = constants.%empty_tuple.type.as.I.impl.F.8be29b.1]
 // CHECK:STDOUT:     %Copy.facet.loc10_34.1: %Copy.type = facet_value constants.%ptr.e8f, (constants.%Copy.lookup_impl_witness.2e6) [symbolic = %Copy.facet.loc10_34.2 (constants.%Copy.facet)]
@@ -1067,10 +1092,12 @@ impl () as I({}) {
 // CHECK:STDOUT: --- generic_method.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %type: type = facet_type <type> [concrete]
 // CHECK:STDOUT:   %.Self: %type = symbolic_binding .Self [symbolic_self]
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %empty_tuple: %empty_tuple.type = tuple_value () [concrete]
+// CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @empty_tuple.type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %pattern_type.cb1: type = pattern_type %empty_tuple.type [concrete]
 // CHECK:STDOUT:   %Copy.type: type = facet_type <@Copy> [concrete]
 // CHECK:STDOUT:   %pattern_type.ce2: type = pattern_type %Copy.type [concrete]
@@ -1080,6 +1107,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %.435d17.2: Core.Form = init_form %U.as_type.255 [symbolic]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.19e4b8.1: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_51.1 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.8be29b.1: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %I.facet: %I.type = facet_value %empty_tuple.type, (%I.impl_witness) [concrete]
 // CHECK:STDOUT:   %T.67d: type = symbolic_binding T, 0 [symbolic]
 // CHECK:STDOUT:   %ptr.e8f: type = ptr_type %T.67d [symbolic]
 // CHECK:STDOUT:   %pattern_type.4f4: type = pattern_type %ptr.e8f [symbolic]
@@ -1198,7 +1226,7 @@ impl () as I({}) {
 // CHECK:STDOUT:   %Copy.facet.loc10_51.2: %Copy.type = facet_value %ptr, (%Copy.lookup_impl_witness) [symbolic = %Copy.facet.loc10_51.2 (constants.%Copy.facet)]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.specific_fn.loc10_51.2: <specific function> = specific_function constants.%empty_tuple.type.as.I.impl.F.8be29b.1, @empty_tuple.type.as.I.impl.F.loc10_51.1(%Copy.facet.loc10_51.2) [symbolic = %empty_tuple.type.as.I.impl.F.specific_fn.loc10_51.2 (constants.%empty_tuple.type.as.I.impl.F.specific_fn)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: %empty_tuple.type, %x.param: @empty_tuple.type.as.I.impl.F.loc10_51.2.%ptr (%ptr.e8f)) -> out %return.param: @empty_tuple.type.as.I.impl.F.loc10_51.2.%ptr (%ptr.e8f) [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_51.1] {
+// CHECK:STDOUT:   fn(%self.param: %empty_tuple.type, %x.param: @empty_tuple.type.as.I.impl.F.loc10_51.2.%ptr (%ptr.e8f)) -> out %return.param: @empty_tuple.type.as.I.impl.F.loc10_51.2.%ptr (%ptr.e8f) [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_51.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet, constants.%T.67d)] {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %F.ref: %empty_tuple.type.as.I.impl.F.type.19e4b8.1 = name_ref F, @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_51.1 [concrete = constants.%empty_tuple.type.as.I.impl.F.8be29b.1]
 // CHECK:STDOUT:     %empty_tuple.type.as.I.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -1246,11 +1274,14 @@ impl () as I({}) {
 // CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [concrete]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
 // CHECK:STDOUT:   %empty_struct: %empty_struct_type = struct_value () [concrete]
+// CHECK:STDOUT:   %I.type.ab5: type = facet_type <@I, @I(%empty_struct_type)> [concrete]
+// CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @empty_tuple.type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %struct_type.b.a.1b0: type = struct_type {.b: %empty_struct_type, .a: %empty_struct_type} [concrete]
 // CHECK:STDOUT:   %.3fc: Core.Form = init_form %struct_type.b.a.1b0 [concrete]
 // CHECK:STDOUT:   %pattern_type.914: type = pattern_type %struct_type.b.a.1b0 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.e82c13.1: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_29.1 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.5f0cef.1: %empty_tuple.type.as.I.impl.F.type.e82c13.1 = struct_value () [concrete]
+// CHECK:STDOUT:   %I.facet: %I.type.ab5 = facet_value %empty_tuple.type, (%I.impl_witness) [concrete]
 // CHECK:STDOUT:   %struct_type.a.b.f95: type = struct_type {.a: %empty_struct_type, .b: %empty_struct_type} [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.type.e82c13.2: type = fn_type @empty_tuple.type.as.I.impl.F.loc10_29.2 [concrete]
 // CHECK:STDOUT:   %empty_tuple.type.as.I.impl.F.5f0cef.2: %empty_tuple.type.as.I.impl.F.type.e82c13.2 = struct_value () [concrete]
@@ -1288,7 +1319,7 @@ impl () as I({}) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_29.1() -> out %return.param: %struct_type.b.a.1b0;
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_29.2() -> out %return.param: %struct_type.a.b.f95 [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_29.1] {
+// CHECK:STDOUT: fn @empty_tuple.type.as.I.impl.F.loc10_29.2() -> out %return.param: %struct_type.a.b.f95 [thunk @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_29.1 for @I.WithSelf.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%empty_struct_type, constants.%I.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %empty_tuple.type.as.I.impl.F.type.e82c13.1 = name_ref F, @empty_tuple.type.as.I.impl.%empty_tuple.type.as.I.impl.F.decl.loc10_29.1 [concrete = constants.%empty_tuple.type.as.I.impl.F.5f0cef.1]
 // CHECK:STDOUT:   %.loc10_29.1: ref %struct_type.b.a.1b0 = temporary_storage
diff --git a/toolchain/check/testdata/impl/import_thunk.carbon b/toolchain/check/testdata/impl/import_thunk.carbon
index 8bb17ca0bb76..55350f5d794c 100644
--- a/toolchain/check/testdata/impl/import_thunk.carbon
+++ b/toolchain/check/testdata/impl/import_thunk.carbon
@@ -164,6 +164,7 @@ fn G() {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Main.import_ref.7f4 = import_ref Main//a, loc5_14, unloaded
 // CHECK:STDOUT:   %Main.F: @I.WithSelf.%I.WithSelf.F.type (%I.WithSelf.F.type.a1f) = import_ref Main//a, F, loaded [symbolic = @I.WithSelf.%I.WithSelf.F (constants.%I.WithSelf.F.cc3)]
+// CHECK:STDOUT:   %I.WithSelf.F.decl: %I.WithSelf.F.type.a1f = fn_decl @I.WithSelf.F [symbolic = @I.WithSelf.%I.WithSelf.F (constants.%I.WithSelf.F.cc3)] {} {}
 // CHECK:STDOUT:   %Main.import_ref.2362f8.2: %I.type = import_ref Main//a, loc4_13, loaded [symbolic = constants.%Self.651]
 // CHECK:STDOUT:   %Main.import_ref.c82 = import_ref Main//a, loc4_13, unloaded
 // CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
@@ -307,7 +308,7 @@ fn G() {
 // CHECK:STDOUT:   %specific_impl_fn.2: <specific function> = specific_impl_function %impl.elem0.2, @Destroy.WithSelf.Op(%Destroy.facet) [symbolic = %specific_impl_fn.2 (constants.%specific_impl_fn)]
 // CHECK:STDOUT:   %bound_method.4: <bound method> = bound_method %.6, %specific_impl_fn.2 [symbolic = %bound_method.4 (constants.%bound_method.fc8)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: %empty_struct_type) [thunk @C.as.I.impl.%C.as.I.impl.F.decl.loc8_24.1] {
+// CHECK:STDOUT:   fn(%x.param: %empty_struct_type) [thunk @C.as.I.impl.%C.as.I.impl.F.decl.loc8_24.1 for imports.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet)] {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %.loc8: @C.as.I.impl.F.loc8_24.2.%C.as.I.impl.F.type (%C.as.I.impl.F.type.cf838e.1) = specific_constant @C.as.I.impl.%C.as.I.impl.F.decl.loc8_24.1, @C.as.I.impl(constants.%Y) [symbolic = %C.as.I.impl.F (constants.%C.as.I.impl.F.421e41.1)]
 // CHECK:STDOUT:     %F.ref: @C.as.I.impl.F.loc8_24.2.%C.as.I.impl.F.type (%C.as.I.impl.F.type.cf838e.1) = name_ref F, %.loc8 [symbolic = %C.as.I.impl.F (constants.%C.as.I.impl.F.421e41.1)]
@@ -405,6 +406,11 @@ fn G() {
 // CHECK:STDOUT:   %I.impl_witness.e46: <witness> = impl_witness imports.%I.impl_witness_table, @C.as.I.impl(%Y) [symbolic]
 // CHECK:STDOUT:   %C.as.I.impl.F.type.627915.1: type = fn_type @C.as.I.impl.F.1, @C.as.I.impl(%Y) [symbolic]
 // CHECK:STDOUT:   %C.as.I.impl.F.7061c2.1: %C.as.I.impl.F.type.627915.1 = struct_value () [symbolic]
+// CHECK:STDOUT:   %C.as.I.impl.F.type.627915.2: type = fn_type @C.as.I.impl.F.2, @C.as.I.impl(%Y) [symbolic]
+// CHECK:STDOUT:   %C.as.I.impl.F.7061c2.2: %C.as.I.impl.F.type.627915.2 = struct_value () [symbolic]
+// CHECK:STDOUT:   %pattern_type.fb2: type = pattern_type %C.c8540f.2 [symbolic]
+// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %C.c8540f.2 [symbolic]
+// CHECK:STDOUT:   %I.facet.330: %I.type = facet_value %C.c8540f.2, (%I.impl_witness.e46) [symbolic]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %Destroy.lookup_impl_witness: <witness> = lookup_impl_witness %C.c8540f.2, @Destroy [symbolic]
 // CHECK:STDOUT:   %Destroy.facet.3bf: %Destroy.type = facet_value %C.c8540f.2, (%Destroy.lookup_impl_witness) [symbolic]
@@ -412,12 +418,8 @@ fn G() {
 // CHECK:STDOUT:   %.634: type = fn_type_with_self_type %Destroy.WithSelf.Op.type.696, %Destroy.facet.3bf [symbolic]
 // CHECK:STDOUT:   %impl.elem0: %.634 = impl_witness_access %Destroy.lookup_impl_witness, element0 [symbolic]
 // CHECK:STDOUT:   %specific_impl_fn: <specific function> = specific_impl_function %impl.elem0, @Destroy.WithSelf.Op(%Destroy.facet.3bf) [symbolic]
-// CHECK:STDOUT:   %pattern_type.fb2: type = pattern_type %C.c8540f.2 [symbolic]
 // CHECK:STDOUT:   %C.val.6cb: %C.c8540f.2 = struct_value () [symbolic]
 // CHECK:STDOUT:   %.5fa: ref %C.c8540f.2 = temporary invalid, %C.val.6cb [symbolic]
-// CHECK:STDOUT:   %C.as.I.impl.F.type.627915.2: type = fn_type @C.as.I.impl.F.2, @C.as.I.impl(%Y) [symbolic]
-// CHECK:STDOUT:   %C.as.I.impl.F.7061c2.2: %C.as.I.impl.F.type.627915.2 = struct_value () [symbolic]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %C.c8540f.2 [symbolic]
 // CHECK:STDOUT:   %bound_method.ff8: <bound method> = bound_method %.5fa, %specific_impl_fn [symbolic]
 // CHECK:STDOUT:   %bound_method.88b: <bound method> = bound_method %.5fa, %impl.elem0 [symbolic]
 // CHECK:STDOUT:   %C.as.I.impl.F.specific_fn.b2d: <specific function> = specific_function %C.as.I.impl.F.7061c2.2, @C.as.I.impl.F.2(%Y) [symbolic]
@@ -426,10 +428,10 @@ fn G() {
 // CHECK:STDOUT:   %C.as.I.impl.F.be0bb4.1: %C.as.I.impl.F.type.1bc610.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %C.as.I.impl.F.type.1bc610.2: type = fn_type @C.as.I.impl.F.1, @C.as.I.impl(%empty_tuple) [concrete]
 // CHECK:STDOUT:   %C.as.I.impl.F.be0bb4.2: %C.as.I.impl.F.type.1bc610.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %I.facet: %I.type = facet_value %C.387, (%I.impl_witness.b70) [concrete]
-// CHECK:STDOUT:   %I.WithSelf.F.type.0c4: type = fn_type @I.WithSelf.F, @I.WithSelf(%I.facet) [concrete]
+// CHECK:STDOUT:   %I.facet.478: %I.type = facet_value %C.387, (%I.impl_witness.b70) [concrete]
+// CHECK:STDOUT:   %I.WithSelf.F.type.0c4: type = fn_type @I.WithSelf.F, @I.WithSelf(%I.facet.478) [concrete]
 // CHECK:STDOUT:   %I.WithSelf.F.b2b: %I.WithSelf.F.type.0c4 = struct_value () [concrete]
-// CHECK:STDOUT:   %.25a: type = fn_type_with_self_type %I.WithSelf.F.type.0c4, %I.facet [concrete]
+// CHECK:STDOUT:   %.25a: type = fn_type_with_self_type %I.WithSelf.F.type.0c4, %I.facet.478 [concrete]
 // CHECK:STDOUT:   %empty_struct: %empty_struct_type = struct_value () [concrete]
 // CHECK:STDOUT:   %C.as.I.impl.F.specific_fn.53944e.1: <specific function> = specific_function %C.as.I.impl.F.be0bb4.2, @C.as.I.impl.F.1(%empty_tuple) [concrete]
 // CHECK:STDOUT:   %pattern_type.678: type = pattern_type %C.387 [concrete]
@@ -458,14 +460,15 @@ fn G() {
 // CHECK:STDOUT:   %Main.import_ref.c90e1a.1: %empty_tuple.type = import_ref Main//b, loc5_10, loaded [symbolic = @C.%X (constants.%X)]
 // CHECK:STDOUT:   %Main.import_ref.a54: %I.assoc_type = import_ref Main//a, loc5_14, loaded [concrete = constants.%assoc0.a42]
 // CHECK:STDOUT:   %Main.F.768 = import_ref Main//a, F, unloaded
+// CHECK:STDOUT:   %I.WithSelf.F.decl: %I.WithSelf.F.type.a1f = fn_decl @I.WithSelf.F [symbolic = @I.WithSelf.%I.WithSelf.F (constants.%I.WithSelf.F.cc3)] {} {}
 // CHECK:STDOUT:   %Main.import_ref.2362f8.2: %I.type = import_ref Main//a, loc4_13, loaded [symbolic = constants.%Self.651]
 // CHECK:STDOUT:   %Main.import_ref.c82 = import_ref Main//a, loc4_13, unloaded
 // CHECK:STDOUT:   %Main.import_ref.972: @I.WithSelf.%I.WithSelf.F.type (%I.WithSelf.F.type.a1f) = import_ref Main//a, loc5_14, loaded [symbolic = @I.WithSelf.%I.WithSelf.F (constants.%I.WithSelf.F.cc3)]
 // CHECK:STDOUT:   %Main.import_ref.e97: <witness> = import_ref Main//b, loc7_32, loaded [symbolic = @C.as.I.impl.%I.impl_witness (constants.%I.impl_witness.e46)]
 // CHECK:STDOUT:   %Main.import_ref.09c: @C.as.I.impl.%C.as.I.impl.F.type.2 (%C.as.I.impl.F.type.627915.1) = import_ref Main//b, loc8_24, loaded [symbolic = @C.as.I.impl.%C.as.I.impl.F.2 (constants.%C.as.I.impl.F.7061c2.1)]
 // CHECK:STDOUT:   %I.impl_witness_table = impl_witness_table (%Main.import_ref.09c), @C.as.I.impl [concrete]
-// CHECK:STDOUT:   %Main.F.d0d: @C.as.I.impl.%C.as.I.impl.F.type.1 (%C.as.I.impl.F.type.627915.2) = import_ref Main//b, F, loaded [symbolic = @C.as.I.impl.%C.as.I.impl.F.1 (constants.%C.as.I.impl.F.7061c2.2)]
 // CHECK:STDOUT:   %Main.import_ref.c90e1a.2: %empty_tuple.type = import_ref Main//b, loc7_15, loaded [symbolic = @C.as.I.impl.%Y (constants.%Y)]
+// CHECK:STDOUT:   %Main.F.d0d: @C.as.I.impl.%C.as.I.impl.F.type.1 (%C.as.I.impl.F.type.627915.2) = import_ref Main//b, F, loaded [symbolic = @C.as.I.impl.%C.as.I.impl.F.1 (constants.%C.as.I.impl.F.7061c2.2)]
 // CHECK:STDOUT:   %Main.import_ref.c90e1a.3: %empty_tuple.type = import_ref Main//b, loc7_15, loaded [symbolic = @C.as.I.impl.%Y (constants.%Y)]
 // CHECK:STDOUT:   %Main.import_ref.2e2: type = import_ref Main//b, loc7_25, loaded [symbolic = @C.as.I.impl.%C (constants.%C.c8540f.2)]
 // CHECK:STDOUT:   %Main.import_ref.91f: type = import_ref Main//b, loc7_30, loaded [concrete = constants.%I.type]
@@ -533,8 +536,8 @@ fn G() {
 // CHECK:STDOUT:   %C: type = class_type @C, @C(constants.%empty_tuple) [concrete = constants.%C.387]
 // CHECK:STDOUT:   %I.ref: type = name_ref I, imports.%Main.I [concrete = constants.%I.type]
 // CHECK:STDOUT:   %F.ref.loc7_11: %I.assoc_type = name_ref F, imports.%Main.import_ref.a54 [concrete = constants.%assoc0.a42]
-// CHECK:STDOUT:   %I.facet: %I.type = facet_value %C, (constants.%I.impl_witness.b70) [concrete = constants.%I.facet]
-// CHECK:STDOUT:   %.loc7_8: %I.type = converted %C, %I.facet [concrete = constants.%I.facet]
+// CHECK:STDOUT:   %I.facet: %I.type = facet_value %C, (constants.%I.impl_witness.b70) [concrete = constants.%I.facet.478]
+// CHECK:STDOUT:   %.loc7_8: %I.type = converted %C, %I.facet [concrete = constants.%I.facet.478]
 // CHECK:STDOUT:   %impl.elem0: %.25a = impl_witness_access constants.%I.impl_witness.b70, element0 [concrete = constants.%C.as.I.impl.F.be0bb4.2]
 // CHECK:STDOUT:   %.loc7_16.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:   %empty_struct.loc7_16.1: %empty_struct_type = struct_value () [concrete = constants.%empty_struct]
@@ -559,7 +562,7 @@ fn G() {
 // CHECK:STDOUT:   fn;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic fn @C.as.I.impl.F.1(imports.%Main.import_ref.c90e1a.2: %empty_tuple.type) [from "b.carbon"] {
+// CHECK:STDOUT: generic fn @C.as.I.impl.F.1(imports.%Main.import_ref.c90e1a.3: %empty_tuple.type) [from "b.carbon"] {
 // CHECK:STDOUT: !definition:
 // CHECK:STDOUT:   %Y: %empty_tuple.type = symbolic_binding Y, 0 [symbolic = %Y (constants.%Y)]
 // CHECK:STDOUT:   %C.as.I.impl.F.type: type = fn_type @C.as.I.impl.F.2, @C.as.I.impl(%Y) [symbolic = %C.as.I.impl.F.type (constants.%C.as.I.impl.F.type.627915.2)]
@@ -578,10 +581,10 @@ fn G() {
 // CHECK:STDOUT:   %specific_impl_fn: <specific function> = specific_impl_function %impl.elem0, @Destroy.WithSelf.Op(%Destroy.facet) [symbolic = %specific_impl_fn (constants.%specific_impl_fn)]
 // CHECK:STDOUT:   %bound_method.2: <bound method> = bound_method %.1, %specific_impl_fn [symbolic = %bound_method.2 (constants.%bound_method.ff8)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn [thunk imports.%Main.F.d0d];
+// CHECK:STDOUT:   fn [thunk imports.%Main.F.d0d for imports.%I.WithSelf.F.decl, @I.WithSelf.F(constants.%I.facet.330)];
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: generic fn @C.as.I.impl.F.2(imports.%Main.import_ref.c90e1a.3: %empty_tuple.type) [from "b.carbon"] {
+// CHECK:STDOUT: generic fn @C.as.I.impl.F.2(imports.%Main.import_ref.c90e1a.2: %empty_tuple.type) [from "b.carbon"] {
 // CHECK:STDOUT:   %Y: %empty_tuple.type = symbolic_binding Y, 0 [symbolic = %Y (constants.%Y)]
 // CHECK:STDOUT:   %C: type = class_type @C, @C(%Y) [symbolic = %C (constants.%C.c8540f.2)]
 // CHECK:STDOUT:   %pattern_type: type = pattern_type %C [symbolic = %pattern_type (constants.%pattern_type.fb2)]
@@ -645,6 +648,8 @@ fn G() {
 // CHECK:STDOUT:   %require_complete => constants.%require_complete
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: specific @I.WithSelf.F(constants.%I.facet.330) {}
+// CHECK:STDOUT:
 // CHECK:STDOUT: specific @C.as.I.impl.F.1(constants.%Y) {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @C.as.I.impl(constants.%empty_tuple) {
@@ -659,9 +664,9 @@ fn G() {
 // CHECK:STDOUT:   %C.as.I.impl.F.2 => constants.%C.as.I.impl.F.be0bb4.2
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: specific @I.WithSelf(constants.%I.facet) {
+// CHECK:STDOUT: specific @I.WithSelf(constants.%I.facet.478) {
 // CHECK:STDOUT: !definition:
-// CHECK:STDOUT:   %Self => constants.%I.facet
+// CHECK:STDOUT:   %Self => constants.%I.facet.478
 // CHECK:STDOUT:   %I.WithSelf.F.type => constants.%I.WithSelf.F.type.0c4
 // CHECK:STDOUT:   %I.WithSelf.F => constants.%I.WithSelf.F.b2b
 // CHECK:STDOUT: }
diff --git a/toolchain/check/testdata/impl/use_assoc_entity.carbon b/toolchain/check/testdata/impl/use_assoc_entity.carbon
index 8c6bc11fd81a..f96fc4724155 100644
--- a/toolchain/check/testdata/impl/use_assoc_entity.carbon
+++ b/toolchain/check/testdata/impl/use_assoc_entity.carbon
@@ -2727,7 +2727,7 @@ fn F() {
 // CHECK:STDOUT:   return <error>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @E.as.J.impl.F.loc27_21.2(%u.param: %i32) -> out %return.param: %i32 [thunk @E.as.J.impl.%E.as.J.impl.F.decl.loc27_21.1] {
+// CHECK:STDOUT: fn @E.as.J.impl.F.loc27_21.2(%u.param: %i32) -> out %return.param: %i32 [thunk @E.as.J.impl.%E.as.J.impl.F.decl.loc27_21.1 for @J.WithSelf.%J.WithSelf.F.decl, @J.WithSelf.F(constants.%J.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %E.as.J.impl.F.type.4b5c2a.1 = name_ref F, @E.as.J.impl.%E.as.J.impl.F.decl.loc27_21.1 [concrete = constants.%E.as.J.impl.F.b4e6ab.1]
 // CHECK:STDOUT:   %E.as.J.impl.F.call: <error> = call %F.ref(<error>)
@@ -3455,7 +3455,7 @@ fn F() {
 // CHECK:STDOUT:   return %.loc23_50
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @empty_tuple.type.as.J2.impl.F.loc23_40.2(%self.param: %empty_tuple.type) -> <error> [thunk @empty_tuple.type.as.J2.impl.%empty_tuple.type.as.J2.impl.F.decl.loc23_40.1] {
+// CHECK:STDOUT: fn @empty_tuple.type.as.J2.impl.F.loc23_40.2(%self.param: %empty_tuple.type) -> <error> [thunk @empty_tuple.type.as.J2.impl.%empty_tuple.type.as.J2.impl.F.decl.loc23_40.1 for @J2.WithSelf.%J2.WithSelf.F.decl, @J2.WithSelf.F(constants.%J2.facet.6c9)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %empty_tuple.type.as.J2.impl.F.type.56bdaf.1 = name_ref F, @empty_tuple.type.as.J2.impl.%empty_tuple.type.as.J2.impl.F.decl.loc23_40.1 [concrete = constants.%empty_tuple.type.as.J2.impl.F.7b8679.1]
 // CHECK:STDOUT:   %empty_tuple.type.as.J2.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -3473,7 +3473,7 @@ fn F() {
 // CHECK:STDOUT:   return %.loc32_53.4
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @C2.as.J2.impl.F.loc32_40.2(%self.param: %C2) -> <error> [thunk @C2.as.J2.impl.%C2.as.J2.impl.F.decl.loc32_40.1] {
+// CHECK:STDOUT: fn @C2.as.J2.impl.F.loc32_40.2(%self.param: %C2) -> <error> [thunk @C2.as.J2.impl.%C2.as.J2.impl.F.decl.loc32_40.1 for @J2.WithSelf.%J2.WithSelf.F.decl, @J2.WithSelf.F(constants.%J2.facet.f19)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %C2.as.J2.impl.F.type.d2a210.1 = name_ref F, @C2.as.J2.impl.%C2.as.J2.impl.F.decl.loc32_40.1 [concrete = constants.%C2.as.J2.impl.F.720bb2.1]
 // CHECK:STDOUT:   %C2.as.J2.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
@@ -3730,7 +3730,7 @@ fn F() {
 // CHECK:STDOUT:   return %.loc26_62
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @empty_tuple.type.as.K.impl.F.loc26_52.2(%self.param: %empty_tuple.type, %v.param: %struct_type.a) -> out %return.param: %struct_type.a [thunk @empty_tuple.type.as.K.impl.%empty_tuple.type.as.K.impl.F.decl.loc26_52.1] {
+// CHECK:STDOUT: fn @empty_tuple.type.as.K.impl.F.loc26_52.2(%self.param: %empty_tuple.type, %v.param: %struct_type.a) -> out %return.param: %struct_type.a [thunk @empty_tuple.type.as.K.impl.%empty_tuple.type.as.K.impl.F.decl.loc26_52.1 for @K.WithSelf.%K.WithSelf.F.decl, @K.WithSelf.F(constants.%K.facet)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %F.ref: %empty_tuple.type.as.K.impl.F.type.1710d5.1 = name_ref F, @empty_tuple.type.as.K.impl.%empty_tuple.type.as.K.impl.F.decl.loc26_52.1 [concrete = constants.%empty_tuple.type.as.K.impl.F.907e52.1]
 // CHECK:STDOUT:   %empty_tuple.type.as.K.impl.F.bound: <bound method> = bound_method %self.param, %F.ref
diff --git a/toolchain/check/testdata/interop/cpp/function/import/default_arg.carbon b/toolchain/check/testdata/interop/cpp/function/import/default_arg.carbon
index 8d448f8d1cfd..426ec89d80c6 100644
--- a/toolchain/check/testdata/interop/cpp/function/import/default_arg.carbon
+++ b/toolchain/check/testdata/interop/cpp/function/import/default_arg.carbon
@@ -478,8 +478,13 @@ fn Call() {
 // CHECK:STDOUT:   %D__carbon_thunk.type: type = fn_type @D__carbon_thunk [concrete]
 // CHECK:STDOUT:   %D__carbon_thunk: %D__carbon_thunk.type = struct_value () [concrete]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
+// CHECK:STDOUT:   %Self.765: %Destroy.type = symbolic_binding Self, 0 [symbolic]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.type.cb2: type = fn_type @Destroy.WithSelf.Op, @Destroy.WithSelf(%Self.765) [symbolic]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.9f1: %Destroy.WithSelf.Op.type.cb2 = struct_value () [symbolic]
 // CHECK:STDOUT:   %X.cpp_destructor.type: type = fn_type @X.cpp_destructor [concrete]
 // CHECK:STDOUT:   %X.cpp_destructor: %X.cpp_destructor.type = struct_value () [concrete]
+// CHECK:STDOUT:   %custom_witness.efb: <witness> = custom_witness (), @Destroy [concrete]
+// CHECK:STDOUT:   %Destroy.facet.2e4: %Destroy.type = facet_value %X, (%custom_witness.efb) [concrete]
 // CHECK:STDOUT:   %X.Op.type: type = fn_type @X.Op [concrete]
 // CHECK:STDOUT:   %X.Op: %X.Op.type = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -632,6 +637,7 @@ fn Call() {
 // CHECK:STDOUT:     %a: %i32 = value_binding a, %a.param
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.decl: %Destroy.WithSelf.Op.type.cb2 = fn_decl @Destroy.WithSelf.Op [symbolic = @Destroy.WithSelf.%Destroy.WithSelf.Op (constants.%Destroy.WithSelf.Op.9f1)] {} {}
 // CHECK:STDOUT:   %X.cpp_destructor.decl: %X.cpp_destructor.type = fn_decl @X.cpp_destructor [concrete = constants.%X.cpp_destructor] {
 // CHECK:STDOUT:     %self.param_patt: %pattern_type.46b = ref_param_pattern [concrete]
 // CHECK:STDOUT:     %self.patt: %pattern_type.46b = at_binding_pattern self, %self.param_patt [concrete]
@@ -829,7 +835,7 @@ fn Call() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @X.cpp_destructor(%self.param: ref %X) = "no_op";
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @X.Op(%self.param: ref %X) [thunk imports.%X.cpp_destructor.decl] {
+// CHECK:STDOUT: fn @X.Op(%self.param: ref %X) [thunk imports.%X.cpp_destructor.decl for imports.%Destroy.WithSelf.Op.decl, @Destroy.WithSelf.Op(constants.%Destroy.facet.2e4)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %Op.ref: %X.cpp_destructor.type = name_ref Op, imports.%X.cpp_destructor.decl [concrete = constants.%X.cpp_destructor]
 // CHECK:STDOUT:   %X.cpp_destructor.bound: <bound method> = bound_method %self.param, %Op.ref
diff --git a/toolchain/check/testdata/interop/cpp/impls/destroy.carbon b/toolchain/check/testdata/interop/cpp/impls/destroy.carbon
index 0671a02631c6..b9882b5e0eb4 100644
--- a/toolchain/check/testdata/interop/cpp/impls/destroy.carbon
+++ b/toolchain/check/testdata/interop/cpp/impls/destroy.carbon
@@ -213,8 +213,12 @@ fn EqualWitnesses(p: Wrap(Cpp.PublicDestructor)*) -> Wrap(Cpp.PublicDestructor)*
 // CHECK:STDOUT:   %empty_struct: %empty_struct_type = struct_value () [concrete]
 // CHECK:STDOUT:   %PublicDestructor.val: %PublicDestructor = struct_value () [concrete]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
+// CHECK:STDOUT:   %Self: %Destroy.type = symbolic_binding Self, 0 [symbolic]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.type.cb2: type = fn_type @Destroy.WithSelf.Op, @Destroy.WithSelf(%Self) [symbolic]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.9f1: %Destroy.WithSelf.Op.type.cb2 = struct_value () [symbolic]
 // CHECK:STDOUT:   %PublicDestructor.cpp_destructor.type: type = fn_type @PublicDestructor.cpp_destructor [concrete]
 // CHECK:STDOUT:   %PublicDestructor.cpp_destructor: %PublicDestructor.cpp_destructor.type = struct_value () [concrete]
+// CHECK:STDOUT:   %custom_witness.efb: <witness> = custom_witness (), @Destroy [concrete]
 // CHECK:STDOUT:   %TrivialDestroy.type: type = fn_type @TrivialDestroy [concrete]
 // CHECK:STDOUT:   %TrivialDestroy: %TrivialDestroy.type = struct_value () [concrete]
 // CHECK:STDOUT:   %TrivialDestructor: type = class_type @TrivialDestructor [concrete]
@@ -222,6 +226,7 @@ fn EqualWitnesses(p: Wrap(Cpp.PublicDestructor)*) -> Wrap(Cpp.PublicDestructor)*
 // CHECK:STDOUT:   %TrivialDestructor.val: %TrivialDestructor = struct_value () [concrete]
 // CHECK:STDOUT:   %TrivialDestructor.cpp_destructor.type: type = fn_type @TrivialDestructor.cpp_destructor [concrete]
 // CHECK:STDOUT:   %TrivialDestructor.cpp_destructor: %TrivialDestructor.cpp_destructor.type = struct_value () [concrete]
+// CHECK:STDOUT:   %Destroy.facet.a0b: %Destroy.type = facet_value %TrivialDestructor, (%custom_witness.efb) [concrete]
 // CHECK:STDOUT:   %TrivialDestructor.Op.type: type = fn_type @TrivialDestructor.Op [concrete]
 // CHECK:STDOUT:   %TrivialDestructor.Op: %TrivialDestructor.Op.type = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -239,6 +244,7 @@ fn EqualWitnesses(p: Wrap(Cpp.PublicDestructor)*) -> Wrap(Cpp.PublicDestructor)*
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %PublicDestructor.decl: type = class_decl @PublicDestructor [concrete = constants.%PublicDestructor] {} {}
 // CHECK:STDOUT:   %Core.Destroy: type = import_ref Core//prelude/parts/destroy, Destroy, loaded [concrete = constants.%Destroy.type]
+// CHECK:STDOUT:   %Destroy.WithSelf.Op.decl: %Destroy.WithSelf.Op.type.cb2 = fn_decl @Destroy.WithSelf.Op [symbolic = @Destroy.WithSelf.%Destroy.WithSelf.Op (constants.%Destroy.WithSelf.Op.9f1)] {} {}
 // CHECK:STDOUT:   %TrivialDestructor.decl: type = class_decl @TrivialDestructor [concrete = constants.%TrivialDestructor] {} {}
 // CHECK:STDOUT:   %TrivialDestructor.cpp_destructor.decl: %TrivialDestructor.cpp_destructor.type = fn_decl @TrivialDestructor.cpp_destructor [concrete = constants.%TrivialDestructor.cpp_destructor] {
 // CHECK:STDOUT:     %self.param_patt: %pattern_type.1b8 = ref_param_pattern [concrete]
@@ -337,7 +343,7 @@ fn EqualWitnesses(p: Wrap(Cpp.PublicDestructor)*) -> Wrap(Cpp.PublicDestructor)*
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @TrivialDestructor.cpp_destructor(%self.param: ref %TrivialDestructor) = "no_op";
 // CHECK:STDOUT:
-// CHECK:STDOUT: fn @TrivialDestructor.Op(%self.param: ref %TrivialDestructor) [thunk imports.%TrivialDestructor.cpp_destructor.decl] {
+// CHECK:STDOUT: fn @TrivialDestructor.Op(%self.param: ref %TrivialDestructor) [thunk imports.%TrivialDestructor.cpp_destructor.decl for imports.%Destroy.WithSelf.Op.decl, @Destroy.WithSelf.Op(constants.%Destroy.facet.a0b)] {
 // CHECK:STDOUT: !entry:
 // CHECK:STDOUT:   %Op.ref: %TrivialDestructor.cpp_destructor.type = name_ref Op, imports.%TrivialDestructor.cpp_destructor.decl [concrete = constants.%TrivialDestructor.cpp_destructor]
 // CHECK:STDOUT:   %TrivialDestructor.cpp_destructor.bound: <bound method> = bound_method %self.param, %Op.ref
diff --git a/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.llp64.carbon b/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.llp64.carbon
index e932e8091bd9..981bcbf8a9a9 100644
--- a/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.llp64.carbon
+++ b/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.llp64.carbon
@@ -1443,32 +1443,32 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %int_1.5a4: %Cpp.long = int_value 1 [concrete]
 // CHECK:STDOUT:   %EqWith.type.494: type = facet_type <@EqWith, @EqWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %EqWith.impl_witness.060: <witness> = impl_witness imports.%EqWith.impl_witness_table.e7b [concrete]
-// CHECK:STDOUT:   %EqWith.facet: %EqWith.type.494 = facet_value %Cpp.long, (%EqWith.impl_witness.060) [concrete]
-// CHECK:STDOUT:   %EqWith.WithSelf.Equal.type.17e: type = fn_type @EqWith.WithSelf.Equal, @EqWith.WithSelf(%Cpp.long, %EqWith.facet) [concrete]
-// CHECK:STDOUT:   %EqWith.WithSelf.NotEqual.type.ed4: type = fn_type @EqWith.WithSelf.NotEqual, @EqWith.WithSelf(%Cpp.long, %EqWith.facet) [concrete]
-// CHECK:STDOUT:   %.e84: type = fn_type_with_self_type %EqWith.WithSelf.Equal.type.17e, %EqWith.facet [concrete]
+// CHECK:STDOUT:   %EqWith.facet.646: %EqWith.type.494 = facet_value %Cpp.long, (%EqWith.impl_witness.060) [concrete]
+// CHECK:STDOUT:   %EqWith.WithSelf.Equal.type.17e: type = fn_type @EqWith.WithSelf.Equal, @EqWith.WithSelf(%Cpp.long, %EqWith.facet.646) [concrete]
+// CHECK:STDOUT:   %EqWith.WithSelf.NotEqual.type.ed4: type = fn_type @EqWith.WithSelf.NotEqual, @EqWith.WithSelf(%Cpp.long, %EqWith.facet.646) [concrete]
+// CHECK:STDOUT:   %.e84: type = fn_type_with_self_type %EqWith.WithSelf.Equal.type.17e, %EqWith.facet.646 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.EqWith.impl.Equal.type.be1: type = fn_type @Cpp.long.as.EqWith.impl.Equal.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.EqWith.impl.Equal.3d5: %Cpp.long.as.EqWith.impl.Equal.type.be1 = struct_value () [concrete]
-// CHECK:STDOUT:   %.681: type = fn_type_with_self_type %EqWith.WithSelf.NotEqual.type.ed4, %EqWith.facet [concrete]
+// CHECK:STDOUT:   %.681: type = fn_type_with_self_type %EqWith.WithSelf.NotEqual.type.ed4, %EqWith.facet.646 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.EqWith.impl.NotEqual.type.35d: type = fn_type @Cpp.long.as.EqWith.impl.NotEqual.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.EqWith.impl.NotEqual.cf9: %Cpp.long.as.EqWith.impl.NotEqual.type.35d = struct_value () [concrete]
 // CHECK:STDOUT:   %OrderedWith.type.a39: type = facet_type <@OrderedWith, @OrderedWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %OrderedWith.impl_witness.109: <witness> = impl_witness imports.%OrderedWith.impl_witness_table.a70 [concrete]
-// CHECK:STDOUT:   %OrderedWith.facet: %OrderedWith.type.a39 = facet_value %Cpp.long, (%OrderedWith.impl_witness.109) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.2ac: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.LessOrEquivalent.type.653: type = fn_type @OrderedWith.WithSelf.LessOrEquivalent, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.Greater.type.df9: type = fn_type @OrderedWith.WithSelf.Greater, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.GreaterOrEquivalent.type.6f9: type = fn_type @OrderedWith.WithSelf.GreaterOrEquivalent, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %.49a: type = fn_type_with_self_type %OrderedWith.WithSelf.Greater.type.df9, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %OrderedWith.facet.88a: %OrderedWith.type.a39 = facet_value %Cpp.long, (%OrderedWith.impl_witness.109) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.2ac: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet.88a) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.LessOrEquivalent.type.653: type = fn_type @OrderedWith.WithSelf.LessOrEquivalent, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet.88a) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.Greater.type.df9: type = fn_type @OrderedWith.WithSelf.Greater, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet.88a) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.GreaterOrEquivalent.type.6f9: type = fn_type @OrderedWith.WithSelf.GreaterOrEquivalent, @OrderedWith.WithSelf(%Cpp.long, %OrderedWith.facet.88a) [concrete]
+// CHECK:STDOUT:   %.49a: type = fn_type_with_self_type %OrderedWith.WithSelf.Greater.type.df9, %OrderedWith.facet.88a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.Greater.type.9ce: type = fn_type @Cpp.long.as.OrderedWith.impl.Greater.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.Greater.1b4: %Cpp.long.as.OrderedWith.impl.Greater.type.9ce = struct_value () [concrete]
-// CHECK:STDOUT:   %.1e2: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.2ac, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.1e2: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.2ac, %OrderedWith.facet.88a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.Less.type.7ac: type = fn_type @Cpp.long.as.OrderedWith.impl.Less.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.Less.4e6: %Cpp.long.as.OrderedWith.impl.Less.type.7ac = struct_value () [concrete]
-// CHECK:STDOUT:   %.eeb: type = fn_type_with_self_type %OrderedWith.WithSelf.GreaterOrEquivalent.type.6f9, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.eeb: type = fn_type_with_self_type %OrderedWith.WithSelf.GreaterOrEquivalent.type.6f9, %OrderedWith.facet.88a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.GreaterOrEquivalent.type.237: type = fn_type @Cpp.long.as.OrderedWith.impl.GreaterOrEquivalent.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.GreaterOrEquivalent.9de: %Cpp.long.as.OrderedWith.impl.GreaterOrEquivalent.type.237 = struct_value () [concrete]
-// CHECK:STDOUT:   %.770: type = fn_type_with_self_type %OrderedWith.WithSelf.LessOrEquivalent.type.653, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.770: type = fn_type_with_self_type %OrderedWith.WithSelf.LessOrEquivalent.type.653, %OrderedWith.facet.88a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.LessOrEquivalent.type.945: type = fn_type @Cpp.long.as.OrderedWith.impl.LessOrEquivalent.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.OrderedWith.impl.LessOrEquivalent.530: %Cpp.long.as.OrderedWith.impl.LessOrEquivalent.type.945 = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -2497,37 +2497,37 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.Negate.impl.Op: %Cpp.long.as.Negate.impl.Op.type = struct_value () [concrete]
 // CHECK:STDOUT:   %AddWith.type.9c2: type = facet_type <@AddWith, @AddWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %AddWith.impl_witness.f2b: <witness> = impl_witness imports.%AddWith.impl_witness_table.819 [concrete]
-// CHECK:STDOUT:   %AddWith.facet: %AddWith.type.9c2 = facet_value %Cpp.long, (%AddWith.impl_witness.f2b) [concrete]
-// CHECK:STDOUT:   %AddWith.WithSelf.Op.type.c8c: type = fn_type @AddWith.WithSelf.Op, @AddWith.WithSelf(%Cpp.long, %AddWith.facet) [concrete]
-// CHECK:STDOUT:   %.a2a: type = fn_type_with_self_type %AddWith.WithSelf.Op.type.c8c, %AddWith.facet [concrete]
+// CHECK:STDOUT:   %AddWith.facet.1b4: %AddWith.type.9c2 = facet_value %Cpp.long, (%AddWith.impl_witness.f2b) [concrete]
+// CHECK:STDOUT:   %AddWith.WithSelf.Op.type.c8c: type = fn_type @AddWith.WithSelf.Op, @AddWith.WithSelf(%Cpp.long, %AddWith.facet.1b4) [concrete]
+// CHECK:STDOUT:   %.a2a: type = fn_type_with_self_type %AddWith.WithSelf.Op.type.c8c, %AddWith.facet.1b4 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddWith.impl.Op.type.c8f: type = fn_type @Cpp.long.as.AddWith.impl.Op.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddWith.impl.Op.c14: %Cpp.long.as.AddWith.impl.Op.type.c8f = struct_value () [concrete]
 // CHECK:STDOUT:   %SubWith.type.e8e: type = facet_type <@SubWith, @SubWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %SubWith.impl_witness.e35: <witness> = impl_witness imports.%SubWith.impl_witness_table.02b [concrete]
-// CHECK:STDOUT:   %SubWith.facet: %SubWith.type.e8e = facet_value %Cpp.long, (%SubWith.impl_witness.e35) [concrete]
-// CHECK:STDOUT:   %SubWith.WithSelf.Op.type.bfa: type = fn_type @SubWith.WithSelf.Op, @SubWith.WithSelf(%Cpp.long, %SubWith.facet) [concrete]
-// CHECK:STDOUT:   %.b47: type = fn_type_with_self_type %SubWith.WithSelf.Op.type.bfa, %SubWith.facet [concrete]
+// CHECK:STDOUT:   %SubWith.facet.f2b: %SubWith.type.e8e = facet_value %Cpp.long, (%SubWith.impl_witness.e35) [concrete]
+// CHECK:STDOUT:   %SubWith.WithSelf.Op.type.bfa: type = fn_type @SubWith.WithSelf.Op, @SubWith.WithSelf(%Cpp.long, %SubWith.facet.f2b) [concrete]
+// CHECK:STDOUT:   %.b47: type = fn_type_with_self_type %SubWith.WithSelf.Op.type.bfa, %SubWith.facet.f2b [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubWith.impl.Op.type.7d6: type = fn_type @Cpp.long.as.SubWith.impl.Op.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubWith.impl.Op.f2a: %Cpp.long.as.SubWith.impl.Op.type.7d6 = struct_value () [concrete]
 // CHECK:STDOUT:   %MulWith.type.a32: type = facet_type <@MulWith, @MulWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %MulWith.impl_witness.7ce: <witness> = impl_witness imports.%MulWith.impl_witness_table.61f [concrete]
-// CHECK:STDOUT:   %MulWith.facet: %MulWith.type.a32 = facet_value %Cpp.long, (%MulWith.impl_witness.7ce) [concrete]
-// CHECK:STDOUT:   %MulWith.WithSelf.Op.type.7fe: type = fn_type @MulWith.WithSelf.Op, @MulWith.WithSelf(%Cpp.long, %MulWith.facet) [concrete]
-// CHECK:STDOUT:   %.b3f: type = fn_type_with_self_type %MulWith.WithSelf.Op.type.7fe, %MulWith.facet [concrete]
+// CHECK:STDOUT:   %MulWith.facet.b05: %MulWith.type.a32 = facet_value %Cpp.long, (%MulWith.impl_witness.7ce) [concrete]
+// CHECK:STDOUT:   %MulWith.WithSelf.Op.type.7fe: type = fn_type @MulWith.WithSelf.Op, @MulWith.WithSelf(%Cpp.long, %MulWith.facet.b05) [concrete]
+// CHECK:STDOUT:   %.b3f: type = fn_type_with_self_type %MulWith.WithSelf.Op.type.7fe, %MulWith.facet.b05 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulWith.impl.Op.type.9a9: type = fn_type @Cpp.long.as.MulWith.impl.Op.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulWith.impl.Op.f69: %Cpp.long.as.MulWith.impl.Op.type.9a9 = struct_value () [concrete]
 // CHECK:STDOUT:   %DivWith.type.0c0: type = facet_type <@DivWith, @DivWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %DivWith.impl_witness.8f1: <witness> = impl_witness imports.%DivWith.impl_witness_table.b92 [concrete]
-// CHECK:STDOUT:   %DivWith.facet: %DivWith.type.0c0 = facet_value %Cpp.long, (%DivWith.impl_witness.8f1) [concrete]
-// CHECK:STDOUT:   %DivWith.WithSelf.Op.type.542: type = fn_type @DivWith.WithSelf.Op, @DivWith.WithSelf(%Cpp.long, %DivWith.facet) [concrete]
-// CHECK:STDOUT:   %.88c: type = fn_type_with_self_type %DivWith.WithSelf.Op.type.542, %DivWith.facet [concrete]
+// CHECK:STDOUT:   %DivWith.facet.d2c: %DivWith.type.0c0 = facet_value %Cpp.long, (%DivWith.impl_witness.8f1) [concrete]
+// CHECK:STDOUT:   %DivWith.WithSelf.Op.type.542: type = fn_type @DivWith.WithSelf.Op, @DivWith.WithSelf(%Cpp.long, %DivWith.facet.d2c) [concrete]
+// CHECK:STDOUT:   %.88c: type = fn_type_with_self_type %DivWith.WithSelf.Op.type.542, %DivWith.facet.d2c [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivWith.impl.Op.type.adc: type = fn_type @Cpp.long.as.DivWith.impl.Op.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivWith.impl.Op.9e1: %Cpp.long.as.DivWith.impl.Op.type.adc = struct_value () [concrete]
 // CHECK:STDOUT:   %ModWith.type.2fc: type = facet_type <@ModWith, @ModWith(%Cpp.long)> [concrete]
 // CHECK:STDOUT:   %ModWith.impl_witness.ad5: <witness> = impl_witness imports.%ModWith.impl_witness_table.578 [concrete]
-// CHECK:STDOUT:   %ModWith.facet: %ModWith.type.2fc = facet_value %Cpp.long, (%ModWith.impl_witness.ad5) [concrete]
-// CHECK:STDOUT:   %ModWith.WithSelf.Op.type.14d: type = fn_type @ModWith.WithSelf.Op, @ModWith.WithSelf(%Cpp.long, %ModWith.facet) [concrete]
-// CHECK:STDOUT:   %.ec5: type = fn_type_with_self_type %ModWith.WithSelf.Op.type.14d, %ModWith.facet [concrete]
+// CHECK:STDOUT:   %ModWith.facet.41b: %ModWith.type.2fc = facet_value %Cpp.long, (%ModWith.impl_witness.ad5) [concrete]
+// CHECK:STDOUT:   %ModWith.WithSelf.Op.type.14d: type = fn_type @ModWith.WithSelf.Op, @ModWith.WithSelf(%Cpp.long, %ModWith.facet.41b) [concrete]
+// CHECK:STDOUT:   %.ec5: type = fn_type_with_self_type %ModWith.WithSelf.Op.type.14d, %ModWith.facet.41b [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModWith.impl.Op.type.d7d: type = fn_type @Cpp.long.as.ModWith.impl.Op.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModWith.impl.Op.922: %Cpp.long.as.ModWith.impl.Op.type.d7d = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -2718,9 +2718,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.ae60d1.1: %Cpp.long.as.AddAssignWith.impl.Op.type.74c6e5.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.type.74c6e5.2: type = fn_type @Cpp.long.as.AddAssignWith.impl.Op.1, @Cpp.long.as.AddAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.ae60d1.2: %Cpp.long.as.AddAssignWith.impl.Op.type.74c6e5.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.bef = facet_value %Cpp.long, (%AddAssignWith.impl_witness.dfa) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.8b3: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%Cpp.long, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.152: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.8b3, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.703: %AddAssignWith.type.bef = facet_value %Cpp.long, (%AddAssignWith.impl_witness.dfa) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.8b3: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%Cpp.long, %AddAssignWith.facet.703) [concrete]
+// CHECK:STDOUT:   %.152: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.8b3, %AddAssignWith.facet.703 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.eef335.1: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.ae60d1.2, @Cpp.long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.eef335.2: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.ae60d1.1, @Cpp.long.as.AddAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %SubAssignWith.type.b12: type = facet_type <@SubAssignWith, @SubAssignWith(%Cpp.long)> [concrete]
@@ -2733,9 +2733,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.fd6475.1: %Cpp.long.as.SubAssignWith.impl.Op.type.658f8e.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.type.658f8e.2: type = fn_type @Cpp.long.as.SubAssignWith.impl.Op.1, @Cpp.long.as.SubAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.fd6475.2: %Cpp.long.as.SubAssignWith.impl.Op.type.658f8e.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %SubAssignWith.facet: %SubAssignWith.type.b12 = facet_value %Cpp.long, (%SubAssignWith.impl_witness.c70) [concrete]
-// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.ee9: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%Cpp.long, %SubAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.c23: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.ee9, %SubAssignWith.facet [concrete]
+// CHECK:STDOUT:   %SubAssignWith.facet.53d: %SubAssignWith.type.b12 = facet_value %Cpp.long, (%SubAssignWith.impl_witness.c70) [concrete]
+// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.ee9: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%Cpp.long, %SubAssignWith.facet.53d) [concrete]
+// CHECK:STDOUT:   %.c23: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.ee9, %SubAssignWith.facet.53d [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.specific_fn.74209d.1: <specific function> = specific_function %Cpp.long.as.SubAssignWith.impl.Op.fd6475.2, @Cpp.long.as.SubAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.specific_fn.74209d.2: <specific function> = specific_function %Cpp.long.as.SubAssignWith.impl.Op.fd6475.1, @Cpp.long.as.SubAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %MulAssignWith.type.59a: type = facet_type <@MulAssignWith, @MulAssignWith(%Cpp.long)> [concrete]
@@ -2748,9 +2748,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.259df5.1: %Cpp.long.as.MulAssignWith.impl.Op.type.792c18.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.type.792c18.2: type = fn_type @Cpp.long.as.MulAssignWith.impl.Op.1, @Cpp.long.as.MulAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.259df5.2: %Cpp.long.as.MulAssignWith.impl.Op.type.792c18.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %MulAssignWith.facet: %MulAssignWith.type.59a = facet_value %Cpp.long, (%MulAssignWith.impl_witness.7cb) [concrete]
-// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.13f: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%Cpp.long, %MulAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.24b: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.13f, %MulAssignWith.facet [concrete]
+// CHECK:STDOUT:   %MulAssignWith.facet.0bc: %MulAssignWith.type.59a = facet_value %Cpp.long, (%MulAssignWith.impl_witness.7cb) [concrete]
+// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.13f: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%Cpp.long, %MulAssignWith.facet.0bc) [concrete]
+// CHECK:STDOUT:   %.24b: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.13f, %MulAssignWith.facet.0bc [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.specific_fn.7330e2.1: <specific function> = specific_function %Cpp.long.as.MulAssignWith.impl.Op.259df5.2, @Cpp.long.as.MulAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.specific_fn.7330e2.2: <specific function> = specific_function %Cpp.long.as.MulAssignWith.impl.Op.259df5.1, @Cpp.long.as.MulAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %DivAssignWith.type.e6d: type = facet_type <@DivAssignWith, @DivAssignWith(%Cpp.long)> [concrete]
@@ -2763,9 +2763,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.42cd1a.1: %Cpp.long.as.DivAssignWith.impl.Op.type.524341.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.type.524341.2: type = fn_type @Cpp.long.as.DivAssignWith.impl.Op.1, @Cpp.long.as.DivAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.42cd1a.2: %Cpp.long.as.DivAssignWith.impl.Op.type.524341.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %DivAssignWith.facet: %DivAssignWith.type.e6d = facet_value %Cpp.long, (%DivAssignWith.impl_witness.376) [concrete]
-// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.220: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%Cpp.long, %DivAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.2e9: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.220, %DivAssignWith.facet [concrete]
+// CHECK:STDOUT:   %DivAssignWith.facet.cd1: %DivAssignWith.type.e6d = facet_value %Cpp.long, (%DivAssignWith.impl_witness.376) [concrete]
+// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.220: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%Cpp.long, %DivAssignWith.facet.cd1) [concrete]
+// CHECK:STDOUT:   %.2e9: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.220, %DivAssignWith.facet.cd1 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.specific_fn.480d87.1: <specific function> = specific_function %Cpp.long.as.DivAssignWith.impl.Op.42cd1a.2, @Cpp.long.as.DivAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.specific_fn.480d87.2: <specific function> = specific_function %Cpp.long.as.DivAssignWith.impl.Op.42cd1a.1, @Cpp.long.as.DivAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %ModAssignWith.type.2a3: type = facet_type <@ModAssignWith, @ModAssignWith(%Cpp.long)> [concrete]
@@ -2778,9 +2778,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.181cf2.1: %Cpp.long.as.ModAssignWith.impl.Op.type.5216aa.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.type.5216aa.2: type = fn_type @Cpp.long.as.ModAssignWith.impl.Op.1, @Cpp.long.as.ModAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.181cf2.2: %Cpp.long.as.ModAssignWith.impl.Op.type.5216aa.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %ModAssignWith.facet: %ModAssignWith.type.2a3 = facet_value %Cpp.long, (%ModAssignWith.impl_witness.474) [concrete]
-// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.66a: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%Cpp.long, %ModAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.b99: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.66a, %ModAssignWith.facet [concrete]
+// CHECK:STDOUT:   %ModAssignWith.facet.8ef: %ModAssignWith.type.2a3 = facet_value %Cpp.long, (%ModAssignWith.impl_witness.474) [concrete]
+// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.66a: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%Cpp.long, %ModAssignWith.facet.8ef) [concrete]
+// CHECK:STDOUT:   %.b99: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.66a, %ModAssignWith.facet.8ef [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.specific_fn.d85655.1: <specific function> = specific_function %Cpp.long.as.ModAssignWith.impl.Op.181cf2.2, @Cpp.long.as.ModAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.specific_fn.d85655.2: <specific function> = specific_function %Cpp.long.as.ModAssignWith.impl.Op.181cf2.1, @Cpp.long.as.ModAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %BitAndAssignWith.type.efd: type = facet_type <@BitAndAssignWith, @BitAndAssignWith(%Cpp.long)> [concrete]
@@ -2793,9 +2793,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.1f3e29.1: %Cpp.long.as.BitAndAssignWith.impl.Op.type.b86dd6.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.type.b86dd6.2: type = fn_type @Cpp.long.as.BitAndAssignWith.impl.Op.1, @Cpp.long.as.BitAndAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.1f3e29.2: %Cpp.long.as.BitAndAssignWith.impl.Op.type.b86dd6.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.facet: %BitAndAssignWith.type.efd = facet_value %Cpp.long, (%BitAndAssignWith.impl_witness.b09) [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.e5c: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%Cpp.long, %BitAndAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.55a: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.e5c, %BitAndAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.facet.6d2: %BitAndAssignWith.type.efd = facet_value %Cpp.long, (%BitAndAssignWith.impl_witness.b09) [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.e5c: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%Cpp.long, %BitAndAssignWith.facet.6d2) [concrete]
+// CHECK:STDOUT:   %.55a: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.e5c, %BitAndAssignWith.facet.6d2 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.specific_fn.32ba3e.1: <specific function> = specific_function %Cpp.long.as.BitAndAssignWith.impl.Op.1f3e29.2, @Cpp.long.as.BitAndAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.specific_fn.32ba3e.2: <specific function> = specific_function %Cpp.long.as.BitAndAssignWith.impl.Op.1f3e29.1, @Cpp.long.as.BitAndAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %BitOrAssignWith.type.b27: type = facet_type <@BitOrAssignWith, @BitOrAssignWith(%Cpp.long)> [concrete]
@@ -2808,9 +2808,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.e40cb6.1: %Cpp.long.as.BitOrAssignWith.impl.Op.type.f6ba26.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.type.f6ba26.2: type = fn_type @Cpp.long.as.BitOrAssignWith.impl.Op.1, @Cpp.long.as.BitOrAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.e40cb6.2: %Cpp.long.as.BitOrAssignWith.impl.Op.type.f6ba26.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.facet: %BitOrAssignWith.type.b27 = facet_value %Cpp.long, (%BitOrAssignWith.impl_witness.942) [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.45b: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%Cpp.long, %BitOrAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.c11: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.45b, %BitOrAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.facet.09c: %BitOrAssignWith.type.b27 = facet_value %Cpp.long, (%BitOrAssignWith.impl_witness.942) [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.45b: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%Cpp.long, %BitOrAssignWith.facet.09c) [concrete]
+// CHECK:STDOUT:   %.c11: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.45b, %BitOrAssignWith.facet.09c [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.specific_fn.de0818.1: <specific function> = specific_function %Cpp.long.as.BitOrAssignWith.impl.Op.e40cb6.2, @Cpp.long.as.BitOrAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.specific_fn.de0818.2: <specific function> = specific_function %Cpp.long.as.BitOrAssignWith.impl.Op.e40cb6.1, @Cpp.long.as.BitOrAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %BitXorAssignWith.type.431: type = facet_type <@BitXorAssignWith, @BitXorAssignWith(%Cpp.long)> [concrete]
@@ -2823,9 +2823,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.db4335.1: %Cpp.long.as.BitXorAssignWith.impl.Op.type.5d3edc.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.type.5d3edc.2: type = fn_type @Cpp.long.as.BitXorAssignWith.impl.Op.1, @Cpp.long.as.BitXorAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.db4335.2: %Cpp.long.as.BitXorAssignWith.impl.Op.type.5d3edc.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.facet: %BitXorAssignWith.type.431 = facet_value %Cpp.long, (%BitXorAssignWith.impl_witness.12c) [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.ce9: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%Cpp.long, %BitXorAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.99b: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.ce9, %BitXorAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.facet.0ad: %BitXorAssignWith.type.431 = facet_value %Cpp.long, (%BitXorAssignWith.impl_witness.12c) [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.ce9: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%Cpp.long, %BitXorAssignWith.facet.0ad) [concrete]
+// CHECK:STDOUT:   %.99b: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.ce9, %BitXorAssignWith.facet.0ad [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.specific_fn.49f737.1: <specific function> = specific_function %Cpp.long.as.BitXorAssignWith.impl.Op.db4335.2, @Cpp.long.as.BitXorAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.specific_fn.49f737.2: <specific function> = specific_function %Cpp.long.as.BitXorAssignWith.impl.Op.db4335.1, @Cpp.long.as.BitXorAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %LeftShiftAssignWith.type.bed: type = facet_type <@LeftShiftAssignWith, @LeftShiftAssignWith(%Cpp.long)> [concrete]
@@ -2838,9 +2838,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.4c9810.1: %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.42094d.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.42094d.2: type = fn_type @Cpp.long.as.LeftShiftAssignWith.impl.Op.1, @Cpp.long.as.LeftShiftAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.4c9810.2: %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.42094d.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.facet: %LeftShiftAssignWith.type.bed = facet_value %Cpp.long, (%LeftShiftAssignWith.impl_witness.d7c) [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.717: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%Cpp.long, %LeftShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.250: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.717, %LeftShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.facet.73c: %LeftShiftAssignWith.type.bed = facet_value %Cpp.long, (%LeftShiftAssignWith.impl_witness.d7c) [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.717: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%Cpp.long, %LeftShiftAssignWith.facet.73c) [concrete]
+// CHECK:STDOUT:   %.250: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.717, %LeftShiftAssignWith.facet.73c [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.specific_fn.de5061.1: <specific function> = specific_function %Cpp.long.as.LeftShiftAssignWith.impl.Op.4c9810.2, @Cpp.long.as.LeftShiftAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.specific_fn.de5061.2: <specific function> = specific_function %Cpp.long.as.LeftShiftAssignWith.impl.Op.4c9810.1, @Cpp.long.as.LeftShiftAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %RightShiftAssignWith.type.222: type = facet_type <@RightShiftAssignWith, @RightShiftAssignWith(%Cpp.long)> [concrete]
@@ -2853,9 +2853,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.d597c8.1: %Cpp.long.as.RightShiftAssignWith.impl.Op.type.7121dc.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.type.7121dc.2: type = fn_type @Cpp.long.as.RightShiftAssignWith.impl.Op.1, @Cpp.long.as.RightShiftAssignWith.impl(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.d597c8.2: %Cpp.long.as.RightShiftAssignWith.impl.Op.type.7121dc.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.facet: %RightShiftAssignWith.type.222 = facet_value %Cpp.long, (%RightShiftAssignWith.impl_witness.44b) [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.302: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%Cpp.long, %RightShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.988: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.302, %RightShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.facet.a87: %RightShiftAssignWith.type.222 = facet_value %Cpp.long, (%RightShiftAssignWith.impl_witness.44b) [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.302: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%Cpp.long, %RightShiftAssignWith.facet.a87) [concrete]
+// CHECK:STDOUT:   %.988: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.302, %RightShiftAssignWith.facet.a87 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.specific_fn.71fc11.1: <specific function> = specific_function %Cpp.long.as.RightShiftAssignWith.impl.Op.d597c8.2, @Cpp.long.as.RightShiftAssignWith.impl.Op.1(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.specific_fn.71fc11.2: <specific function> = specific_function %Cpp.long.as.RightShiftAssignWith.impl.Op.d597c8.1, @Cpp.long.as.RightShiftAssignWith.impl.Op.2(%ImplicitAs.facet.293) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc9_3.2 [concrete]
@@ -3137,9 +3137,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.18480a.1: %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.2: type = fn_type @Cpp.long.as.AddAssignWith.impl.Op.1, @Cpp.long.as.AddAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.18480a.2: %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.794 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.8a4) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.7e7: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i32, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.3bf: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.7e7, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.a4a: %AddAssignWith.type.794 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.8a4) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.7e7: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i32, %AddAssignWith.facet.a4a) [concrete]
+// CHECK:STDOUT:   %.3bf: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.7e7, %AddAssignWith.facet.a4a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.c51759.1: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.18480a.2, @Cpp.long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.595: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%Cpp.long, %ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %.d59: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.595, %ImplicitAs.facet.87f [concrete]
@@ -3156,9 +3156,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.3151e9.1: %Cpp.long.as.SubAssignWith.impl.Op.type.007151.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.type.007151.2: type = fn_type @Cpp.long.as.SubAssignWith.impl.Op.1, @Cpp.long.as.SubAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.3151e9.2: %Cpp.long.as.SubAssignWith.impl.Op.type.007151.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %SubAssignWith.facet: %SubAssignWith.type.ab0 = facet_value %Cpp.long, (%SubAssignWith.impl_witness.cde) [concrete]
-// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.b30: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%i32, %SubAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.0e9: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.b30, %SubAssignWith.facet [concrete]
+// CHECK:STDOUT:   %SubAssignWith.facet.0b8: %SubAssignWith.type.ab0 = facet_value %Cpp.long, (%SubAssignWith.impl_witness.cde) [concrete]
+// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.b30: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%i32, %SubAssignWith.facet.0b8) [concrete]
+// CHECK:STDOUT:   %.0e9: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.b30, %SubAssignWith.facet.0b8 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.specific_fn.f4a251.1: <specific function> = specific_function %Cpp.long.as.SubAssignWith.impl.Op.3151e9.2, @Cpp.long.as.SubAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.SubAssignWith.impl.Op.specific_fn.f4a251.2: <specific function> = specific_function %Cpp.long.as.SubAssignWith.impl.Op.3151e9.1, @Cpp.long.as.SubAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %MulAssignWith.type.743: type = facet_type <@MulAssignWith, @MulAssignWith(%i32)> [concrete]
@@ -3171,9 +3171,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.3df17e.1: %Cpp.long.as.MulAssignWith.impl.Op.type.249066.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.type.249066.2: type = fn_type @Cpp.long.as.MulAssignWith.impl.Op.1, @Cpp.long.as.MulAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.3df17e.2: %Cpp.long.as.MulAssignWith.impl.Op.type.249066.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %MulAssignWith.facet: %MulAssignWith.type.743 = facet_value %Cpp.long, (%MulAssignWith.impl_witness.10f) [concrete]
-// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.bff: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%i32, %MulAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.761: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.bff, %MulAssignWith.facet [concrete]
+// CHECK:STDOUT:   %MulAssignWith.facet.1bb: %MulAssignWith.type.743 = facet_value %Cpp.long, (%MulAssignWith.impl_witness.10f) [concrete]
+// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.bff: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%i32, %MulAssignWith.facet.1bb) [concrete]
+// CHECK:STDOUT:   %.761: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.bff, %MulAssignWith.facet.1bb [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.specific_fn.2a0ec5.1: <specific function> = specific_function %Cpp.long.as.MulAssignWith.impl.Op.3df17e.2, @Cpp.long.as.MulAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.MulAssignWith.impl.Op.specific_fn.2a0ec5.2: <specific function> = specific_function %Cpp.long.as.MulAssignWith.impl.Op.3df17e.1, @Cpp.long.as.MulAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %DivAssignWith.type.786: type = facet_type <@DivAssignWith, @DivAssignWith(%i32)> [concrete]
@@ -3186,9 +3186,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.95c3cb.1: %Cpp.long.as.DivAssignWith.impl.Op.type.f3a6e1.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.type.f3a6e1.2: type = fn_type @Cpp.long.as.DivAssignWith.impl.Op.1, @Cpp.long.as.DivAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.95c3cb.2: %Cpp.long.as.DivAssignWith.impl.Op.type.f3a6e1.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %DivAssignWith.facet: %DivAssignWith.type.786 = facet_value %Cpp.long, (%DivAssignWith.impl_witness.0ea) [concrete]
-// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.99d: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%i32, %DivAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.d78: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.99d, %DivAssignWith.facet [concrete]
+// CHECK:STDOUT:   %DivAssignWith.facet.ae3: %DivAssignWith.type.786 = facet_value %Cpp.long, (%DivAssignWith.impl_witness.0ea) [concrete]
+// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.99d: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%i32, %DivAssignWith.facet.ae3) [concrete]
+// CHECK:STDOUT:   %.d78: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.99d, %DivAssignWith.facet.ae3 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.specific_fn.63c0e6.1: <specific function> = specific_function %Cpp.long.as.DivAssignWith.impl.Op.95c3cb.2, @Cpp.long.as.DivAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.DivAssignWith.impl.Op.specific_fn.63c0e6.2: <specific function> = specific_function %Cpp.long.as.DivAssignWith.impl.Op.95c3cb.1, @Cpp.long.as.DivAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %ModAssignWith.type.e49: type = facet_type <@ModAssignWith, @ModAssignWith(%i32)> [concrete]
@@ -3201,9 +3201,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.a5ea74.1: %Cpp.long.as.ModAssignWith.impl.Op.type.1dde31.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.type.1dde31.2: type = fn_type @Cpp.long.as.ModAssignWith.impl.Op.1, @Cpp.long.as.ModAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.a5ea74.2: %Cpp.long.as.ModAssignWith.impl.Op.type.1dde31.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %ModAssignWith.facet: %ModAssignWith.type.e49 = facet_value %Cpp.long, (%ModAssignWith.impl_witness.b4e) [concrete]
-// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.cae: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%i32, %ModAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.7f1: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.cae, %ModAssignWith.facet [concrete]
+// CHECK:STDOUT:   %ModAssignWith.facet.3d8: %ModAssignWith.type.e49 = facet_value %Cpp.long, (%ModAssignWith.impl_witness.b4e) [concrete]
+// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.cae: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%i32, %ModAssignWith.facet.3d8) [concrete]
+// CHECK:STDOUT:   %.7f1: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.cae, %ModAssignWith.facet.3d8 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.specific_fn.1bddd2.1: <specific function> = specific_function %Cpp.long.as.ModAssignWith.impl.Op.a5ea74.2, @Cpp.long.as.ModAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.ModAssignWith.impl.Op.specific_fn.1bddd2.2: <specific function> = specific_function %Cpp.long.as.ModAssignWith.impl.Op.a5ea74.1, @Cpp.long.as.ModAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %BitAndAssignWith.type.d65: type = facet_type <@BitAndAssignWith, @BitAndAssignWith(%i32)> [concrete]
@@ -3216,9 +3216,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.3b7601.1: %Cpp.long.as.BitAndAssignWith.impl.Op.type.9b8168.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.type.9b8168.2: type = fn_type @Cpp.long.as.BitAndAssignWith.impl.Op.1, @Cpp.long.as.BitAndAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.3b7601.2: %Cpp.long.as.BitAndAssignWith.impl.Op.type.9b8168.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.facet: %BitAndAssignWith.type.d65 = facet_value %Cpp.long, (%BitAndAssignWith.impl_witness.84d) [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.400: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%i32, %BitAndAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.fd7: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.400, %BitAndAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.facet.479: %BitAndAssignWith.type.d65 = facet_value %Cpp.long, (%BitAndAssignWith.impl_witness.84d) [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.400: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%i32, %BitAndAssignWith.facet.479) [concrete]
+// CHECK:STDOUT:   %.fd7: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.400, %BitAndAssignWith.facet.479 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.specific_fn.94318e.1: <specific function> = specific_function %Cpp.long.as.BitAndAssignWith.impl.Op.3b7601.2, @Cpp.long.as.BitAndAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitAndAssignWith.impl.Op.specific_fn.94318e.2: <specific function> = specific_function %Cpp.long.as.BitAndAssignWith.impl.Op.3b7601.1, @Cpp.long.as.BitAndAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %BitOrAssignWith.type.6e9: type = facet_type <@BitOrAssignWith, @BitOrAssignWith(%i32)> [concrete]
@@ -3231,9 +3231,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.dcd7c4.1: %Cpp.long.as.BitOrAssignWith.impl.Op.type.198694.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.type.198694.2: type = fn_type @Cpp.long.as.BitOrAssignWith.impl.Op.1, @Cpp.long.as.BitOrAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.dcd7c4.2: %Cpp.long.as.BitOrAssignWith.impl.Op.type.198694.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.facet: %BitOrAssignWith.type.6e9 = facet_value %Cpp.long, (%BitOrAssignWith.impl_witness.0b0) [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.ef7: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%i32, %BitOrAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.7ba: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.ef7, %BitOrAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.facet.848: %BitOrAssignWith.type.6e9 = facet_value %Cpp.long, (%BitOrAssignWith.impl_witness.0b0) [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.ef7: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%i32, %BitOrAssignWith.facet.848) [concrete]
+// CHECK:STDOUT:   %.7ba: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.ef7, %BitOrAssignWith.facet.848 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.specific_fn.c12656.1: <specific function> = specific_function %Cpp.long.as.BitOrAssignWith.impl.Op.dcd7c4.2, @Cpp.long.as.BitOrAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitOrAssignWith.impl.Op.specific_fn.c12656.2: <specific function> = specific_function %Cpp.long.as.BitOrAssignWith.impl.Op.dcd7c4.1, @Cpp.long.as.BitOrAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %BitXorAssignWith.type.ea8: type = facet_type <@BitXorAssignWith, @BitXorAssignWith(%i32)> [concrete]
@@ -3246,9 +3246,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.1793e8.1: %Cpp.long.as.BitXorAssignWith.impl.Op.type.0c822c.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.type.0c822c.2: type = fn_type @Cpp.long.as.BitXorAssignWith.impl.Op.1, @Cpp.long.as.BitXorAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.1793e8.2: %Cpp.long.as.BitXorAssignWith.impl.Op.type.0c822c.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.facet: %BitXorAssignWith.type.ea8 = facet_value %Cpp.long, (%BitXorAssignWith.impl_witness.77c) [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.a67: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%i32, %BitXorAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.03f: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.a67, %BitXorAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.facet.3f6: %BitXorAssignWith.type.ea8 = facet_value %Cpp.long, (%BitXorAssignWith.impl_witness.77c) [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.a67: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%i32, %BitXorAssignWith.facet.3f6) [concrete]
+// CHECK:STDOUT:   %.03f: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.a67, %BitXorAssignWith.facet.3f6 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.specific_fn.1d9822.1: <specific function> = specific_function %Cpp.long.as.BitXorAssignWith.impl.Op.1793e8.2, @Cpp.long.as.BitXorAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.BitXorAssignWith.impl.Op.specific_fn.1d9822.2: <specific function> = specific_function %Cpp.long.as.BitXorAssignWith.impl.Op.1793e8.1, @Cpp.long.as.BitXorAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %LeftShiftAssignWith.type.92b: type = facet_type <@LeftShiftAssignWith, @LeftShiftAssignWith(%i32)> [concrete]
@@ -3261,9 +3261,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.ba3cb3.1: %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.8bb9f4.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.8bb9f4.2: type = fn_type @Cpp.long.as.LeftShiftAssignWith.impl.Op.1, @Cpp.long.as.LeftShiftAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.ba3cb3.2: %Cpp.long.as.LeftShiftAssignWith.impl.Op.type.8bb9f4.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.facet: %LeftShiftAssignWith.type.92b = facet_value %Cpp.long, (%LeftShiftAssignWith.impl_witness.aa9) [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.483: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%i32, %LeftShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.f43: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.483, %LeftShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.facet.4eb: %LeftShiftAssignWith.type.92b = facet_value %Cpp.long, (%LeftShiftAssignWith.impl_witness.aa9) [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.483: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%i32, %LeftShiftAssignWith.facet.4eb) [concrete]
+// CHECK:STDOUT:   %.f43: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.483, %LeftShiftAssignWith.facet.4eb [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.specific_fn.dc5ccd.1: <specific function> = specific_function %Cpp.long.as.LeftShiftAssignWith.impl.Op.ba3cb3.2, @Cpp.long.as.LeftShiftAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.LeftShiftAssignWith.impl.Op.specific_fn.dc5ccd.2: <specific function> = specific_function %Cpp.long.as.LeftShiftAssignWith.impl.Op.ba3cb3.1, @Cpp.long.as.LeftShiftAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %RightShiftAssignWith.type.8ae: type = facet_type <@RightShiftAssignWith, @RightShiftAssignWith(%i32)> [concrete]
@@ -3276,9 +3276,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.914893.1: %Cpp.long.as.RightShiftAssignWith.impl.Op.type.9da311.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.type.9da311.2: type = fn_type @Cpp.long.as.RightShiftAssignWith.impl.Op.1, @Cpp.long.as.RightShiftAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.914893.2: %Cpp.long.as.RightShiftAssignWith.impl.Op.type.9da311.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.facet: %RightShiftAssignWith.type.8ae = facet_value %Cpp.long, (%RightShiftAssignWith.impl_witness.767) [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.b3d: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%i32, %RightShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.55e: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.b3d, %RightShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.facet.669: %RightShiftAssignWith.type.8ae = facet_value %Cpp.long, (%RightShiftAssignWith.impl_witness.767) [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.b3d: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%i32, %RightShiftAssignWith.facet.669) [concrete]
+// CHECK:STDOUT:   %.55e: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.b3d, %RightShiftAssignWith.facet.669 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.specific_fn.96f972.1: <specific function> = specific_function %Cpp.long.as.RightShiftAssignWith.impl.Op.914893.2, @Cpp.long.as.RightShiftAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.RightShiftAssignWith.impl.Op.specific_fn.96f972.2: <specific function> = specific_function %Cpp.long.as.RightShiftAssignWith.impl.Op.914893.1, @Cpp.long.as.RightShiftAssignWith.impl.Op.2(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc9_3.2 [concrete]
@@ -3626,9 +3626,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.025560.1: %Cpp.long.as.AddAssignWith.impl.Op.type.dedb88.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.type.dedb88.2: type = fn_type @Cpp.long.as.AddAssignWith.impl.Op.1, @Cpp.long.as.AddAssignWith.impl(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.025560.2: %Cpp.long.as.AddAssignWith.impl.Op.type.dedb88.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.761 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.857) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.964: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(Core.IntLiteral, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.e15: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.964, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.4f9: %AddAssignWith.type.761 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.857) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.964: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(Core.IntLiteral, %AddAssignWith.facet.4f9) [concrete]
+// CHECK:STDOUT:   %.e15: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.964, %AddAssignWith.facet.4f9 [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.3f8ea9.1: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.025560.2, @Cpp.long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.3f8ea9.2: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.025560.1, @Cpp.long.as.AddAssignWith.impl.Op.2(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc8_3.2 [concrete]
@@ -3748,9 +3748,9 @@ fn CopyUnsignedLong() {
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.18480a.1: %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.2: type = fn_type @Cpp.long.as.AddAssignWith.impl.Op.1, @Cpp.long.as.AddAssignWith.impl(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.18480a.2: %Cpp.long.as.AddAssignWith.impl.Op.type.88b7ef.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.794 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.8a4) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.7e7: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i32, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.3bf: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.7e7, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.a4a: %AddAssignWith.type.794 = facet_value %Cpp.long, (%AddAssignWith.impl_witness.8a4) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.7e7: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i32, %AddAssignWith.facet.a4a) [concrete]
+// CHECK:STDOUT:   %.3bf: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.7e7, %AddAssignWith.facet.a4a [concrete]
 // CHECK:STDOUT:   %Cpp.long.as.AddAssignWith.impl.Op.specific_fn.c51759.1: <specific function> = specific_function %Cpp.long.as.AddAssignWith.impl.Op.18480a.2, @Cpp.long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.595: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%Cpp.long, %ImplicitAs.facet.87f) [concrete]
 // CHECK:STDOUT:   %.d59: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.595, %ImplicitAs.facet.87f [concrete]
diff --git a/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.lp64.carbon b/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.lp64.carbon
index e9cbbf19f417..00dd6a4329f9 100644
--- a/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.lp64.carbon
+++ b/toolchain/check/testdata/interop/cpp/primitive_types/long_and_long_long.lp64.carbon
@@ -1369,32 +1369,32 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %int_1.092: %Cpp.long_long = int_value 1 [concrete]
 // CHECK:STDOUT:   %EqWith.type.4be: type = facet_type <@EqWith, @EqWith(%Cpp.long_long)> [concrete]
 // CHECK:STDOUT:   %EqWith.impl_witness.891: <witness> = impl_witness imports.%EqWith.impl_witness_table.dc5 [concrete]
-// CHECK:STDOUT:   %EqWith.facet: %EqWith.type.4be = facet_value %Cpp.long_long, (%EqWith.impl_witness.891) [concrete]
-// CHECK:STDOUT:   %EqWith.WithSelf.Equal.type.ca7: type = fn_type @EqWith.WithSelf.Equal, @EqWith.WithSelf(%Cpp.long_long, %EqWith.facet) [concrete]
-// CHECK:STDOUT:   %EqWith.WithSelf.NotEqual.type.41f: type = fn_type @EqWith.WithSelf.NotEqual, @EqWith.WithSelf(%Cpp.long_long, %EqWith.facet) [concrete]
-// CHECK:STDOUT:   %.b62: type = fn_type_with_self_type %EqWith.WithSelf.Equal.type.ca7, %EqWith.facet [concrete]
+// CHECK:STDOUT:   %EqWith.facet.06c: %EqWith.type.4be = facet_value %Cpp.long_long, (%EqWith.impl_witness.891) [concrete]
+// CHECK:STDOUT:   %EqWith.WithSelf.Equal.type.ca7: type = fn_type @EqWith.WithSelf.Equal, @EqWith.WithSelf(%Cpp.long_long, %EqWith.facet.06c) [concrete]
+// CHECK:STDOUT:   %EqWith.WithSelf.NotEqual.type.41f: type = fn_type @EqWith.WithSelf.NotEqual, @EqWith.WithSelf(%Cpp.long_long, %EqWith.facet.06c) [concrete]
+// CHECK:STDOUT:   %.b62: type = fn_type_with_self_type %EqWith.WithSelf.Equal.type.ca7, %EqWith.facet.06c [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.EqWith.impl.Equal.type.5dc: type = fn_type @Cpp.long_long.as.EqWith.impl.Equal.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.EqWith.impl.Equal.1f3: %Cpp.long_long.as.EqWith.impl.Equal.type.5dc = struct_value () [concrete]
-// CHECK:STDOUT:   %.81b: type = fn_type_with_self_type %EqWith.WithSelf.NotEqual.type.41f, %EqWith.facet [concrete]
+// CHECK:STDOUT:   %.81b: type = fn_type_with_self_type %EqWith.WithSelf.NotEqual.type.41f, %EqWith.facet.06c [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.EqWith.impl.NotEqual.type.282: type = fn_type @Cpp.long_long.as.EqWith.impl.NotEqual.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.EqWith.impl.NotEqual.8e9: %Cpp.long_long.as.EqWith.impl.NotEqual.type.282 = struct_value () [concrete]
 // CHECK:STDOUT:   %OrderedWith.type.65e: type = facet_type <@OrderedWith, @OrderedWith(%Cpp.long_long)> [concrete]
 // CHECK:STDOUT:   %OrderedWith.impl_witness.f2c: <witness> = impl_witness imports.%OrderedWith.impl_witness_table.547 [concrete]
-// CHECK:STDOUT:   %OrderedWith.facet: %OrderedWith.type.65e = facet_value %Cpp.long_long, (%OrderedWith.impl_witness.f2c) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.6ab: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.LessOrEquivalent.type.b52: type = fn_type @OrderedWith.WithSelf.LessOrEquivalent, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.Greater.type.969: type = fn_type @OrderedWith.WithSelf.Greater, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %OrderedWith.WithSelf.GreaterOrEquivalent.type.c71: type = fn_type @OrderedWith.WithSelf.GreaterOrEquivalent, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet) [concrete]
-// CHECK:STDOUT:   %.ba7: type = fn_type_with_self_type %OrderedWith.WithSelf.Greater.type.969, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %OrderedWith.facet.20f: %OrderedWith.type.65e = facet_value %Cpp.long_long, (%OrderedWith.impl_witness.f2c) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.Less.type.6ab: type = fn_type @OrderedWith.WithSelf.Less, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet.20f) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.LessOrEquivalent.type.b52: type = fn_type @OrderedWith.WithSelf.LessOrEquivalent, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet.20f) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.Greater.type.969: type = fn_type @OrderedWith.WithSelf.Greater, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet.20f) [concrete]
+// CHECK:STDOUT:   %OrderedWith.WithSelf.GreaterOrEquivalent.type.c71: type = fn_type @OrderedWith.WithSelf.GreaterOrEquivalent, @OrderedWith.WithSelf(%Cpp.long_long, %OrderedWith.facet.20f) [concrete]
+// CHECK:STDOUT:   %.ba7: type = fn_type_with_self_type %OrderedWith.WithSelf.Greater.type.969, %OrderedWith.facet.20f [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.Greater.type.366: type = fn_type @Cpp.long_long.as.OrderedWith.impl.Greater.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.Greater.98e: %Cpp.long_long.as.OrderedWith.impl.Greater.type.366 = struct_value () [concrete]
-// CHECK:STDOUT:   %.3bb: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.6ab, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.3bb: type = fn_type_with_self_type %OrderedWith.WithSelf.Less.type.6ab, %OrderedWith.facet.20f [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.Less.type.14b: type = fn_type @Cpp.long_long.as.OrderedWith.impl.Less.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.Less.806: %Cpp.long_long.as.OrderedWith.impl.Less.type.14b = struct_value () [concrete]
-// CHECK:STDOUT:   %.ab6: type = fn_type_with_self_type %OrderedWith.WithSelf.GreaterOrEquivalent.type.c71, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.ab6: type = fn_type_with_self_type %OrderedWith.WithSelf.GreaterOrEquivalent.type.c71, %OrderedWith.facet.20f [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.GreaterOrEquivalent.type.58e: type = fn_type @Cpp.long_long.as.OrderedWith.impl.GreaterOrEquivalent.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.GreaterOrEquivalent.90e: %Cpp.long_long.as.OrderedWith.impl.GreaterOrEquivalent.type.58e = struct_value () [concrete]
-// CHECK:STDOUT:   %.ae4: type = fn_type_with_self_type %OrderedWith.WithSelf.LessOrEquivalent.type.b52, %OrderedWith.facet [concrete]
+// CHECK:STDOUT:   %.ae4: type = fn_type_with_self_type %OrderedWith.WithSelf.LessOrEquivalent.type.b52, %OrderedWith.facet.20f [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.LessOrEquivalent.type.cba: type = fn_type @Cpp.long_long.as.OrderedWith.impl.LessOrEquivalent.3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.OrderedWith.impl.LessOrEquivalent.01d: %Cpp.long_long.as.OrderedWith.impl.LessOrEquivalent.type.cba = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -2436,9 +2436,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.9f5215.1: %Cpp.long_long.as.AddAssignWith.impl.Op.type.764577.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.type.764577.2: type = fn_type @Cpp.long_long.as.AddAssignWith.impl.Op.1, @Cpp.long_long.as.AddAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.9f5215.2: %Cpp.long_long.as.AddAssignWith.impl.Op.type.764577.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.2ec = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.bf6) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.03b: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%Cpp.long_long, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.e56: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.03b, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.628: %AddAssignWith.type.2ec = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.bf6) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.03b: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%Cpp.long_long, %AddAssignWith.facet.628) [concrete]
+// CHECK:STDOUT:   %.e56: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.03b, %AddAssignWith.facet.628 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.cf84ae.1: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.9f5215.2, @Cpp.long_long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.cf84ae.2: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.9f5215.1, @Cpp.long_long.as.AddAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %SubAssignWith.type.b35: type = facet_type <@SubAssignWith, @SubAssignWith(%Cpp.long_long)> [concrete]
@@ -2451,9 +2451,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.055560.1: %Cpp.long_long.as.SubAssignWith.impl.Op.type.bbcd3f.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.type.bbcd3f.2: type = fn_type @Cpp.long_long.as.SubAssignWith.impl.Op.1, @Cpp.long_long.as.SubAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.055560.2: %Cpp.long_long.as.SubAssignWith.impl.Op.type.bbcd3f.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %SubAssignWith.facet: %SubAssignWith.type.b35 = facet_value %Cpp.long_long, (%SubAssignWith.impl_witness.ca9) [concrete]
-// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.010: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%Cpp.long_long, %SubAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.d9d: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.010, %SubAssignWith.facet [concrete]
+// CHECK:STDOUT:   %SubAssignWith.facet.0a2: %SubAssignWith.type.b35 = facet_value %Cpp.long_long, (%SubAssignWith.impl_witness.ca9) [concrete]
+// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.010: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%Cpp.long_long, %SubAssignWith.facet.0a2) [concrete]
+// CHECK:STDOUT:   %.d9d: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.010, %SubAssignWith.facet.0a2 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.specific_fn.3f0e56.1: <specific function> = specific_function %Cpp.long_long.as.SubAssignWith.impl.Op.055560.2, @Cpp.long_long.as.SubAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.specific_fn.3f0e56.2: <specific function> = specific_function %Cpp.long_long.as.SubAssignWith.impl.Op.055560.1, @Cpp.long_long.as.SubAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %MulAssignWith.type.112: type = facet_type <@MulAssignWith, @MulAssignWith(%Cpp.long_long)> [concrete]
@@ -2466,9 +2466,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.615bbe.1: %Cpp.long_long.as.MulAssignWith.impl.Op.type.930c4a.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.type.930c4a.2: type = fn_type @Cpp.long_long.as.MulAssignWith.impl.Op.1, @Cpp.long_long.as.MulAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.615bbe.2: %Cpp.long_long.as.MulAssignWith.impl.Op.type.930c4a.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %MulAssignWith.facet: %MulAssignWith.type.112 = facet_value %Cpp.long_long, (%MulAssignWith.impl_witness.6f5) [concrete]
-// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.16b: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%Cpp.long_long, %MulAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.3df: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.16b, %MulAssignWith.facet [concrete]
+// CHECK:STDOUT:   %MulAssignWith.facet.3ad: %MulAssignWith.type.112 = facet_value %Cpp.long_long, (%MulAssignWith.impl_witness.6f5) [concrete]
+// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.16b: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%Cpp.long_long, %MulAssignWith.facet.3ad) [concrete]
+// CHECK:STDOUT:   %.3df: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.16b, %MulAssignWith.facet.3ad [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.specific_fn.54521e.1: <specific function> = specific_function %Cpp.long_long.as.MulAssignWith.impl.Op.615bbe.2, @Cpp.long_long.as.MulAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.specific_fn.54521e.2: <specific function> = specific_function %Cpp.long_long.as.MulAssignWith.impl.Op.615bbe.1, @Cpp.long_long.as.MulAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %DivAssignWith.type.45d: type = facet_type <@DivAssignWith, @DivAssignWith(%Cpp.long_long)> [concrete]
@@ -2481,9 +2481,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.edd3fd.1: %Cpp.long_long.as.DivAssignWith.impl.Op.type.0750e7.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.type.0750e7.2: type = fn_type @Cpp.long_long.as.DivAssignWith.impl.Op.1, @Cpp.long_long.as.DivAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.edd3fd.2: %Cpp.long_long.as.DivAssignWith.impl.Op.type.0750e7.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %DivAssignWith.facet: %DivAssignWith.type.45d = facet_value %Cpp.long_long, (%DivAssignWith.impl_witness.18b) [concrete]
-// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.2f0: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%Cpp.long_long, %DivAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.e87: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.2f0, %DivAssignWith.facet [concrete]
+// CHECK:STDOUT:   %DivAssignWith.facet.328: %DivAssignWith.type.45d = facet_value %Cpp.long_long, (%DivAssignWith.impl_witness.18b) [concrete]
+// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.2f0: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%Cpp.long_long, %DivAssignWith.facet.328) [concrete]
+// CHECK:STDOUT:   %.e87: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.2f0, %DivAssignWith.facet.328 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.specific_fn.615d14.1: <specific function> = specific_function %Cpp.long_long.as.DivAssignWith.impl.Op.edd3fd.2, @Cpp.long_long.as.DivAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.specific_fn.615d14.2: <specific function> = specific_function %Cpp.long_long.as.DivAssignWith.impl.Op.edd3fd.1, @Cpp.long_long.as.DivAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %ModAssignWith.type.a2e: type = facet_type <@ModAssignWith, @ModAssignWith(%Cpp.long_long)> [concrete]
@@ -2496,9 +2496,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.b6ce41.1: %Cpp.long_long.as.ModAssignWith.impl.Op.type.423758.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.type.423758.2: type = fn_type @Cpp.long_long.as.ModAssignWith.impl.Op.1, @Cpp.long_long.as.ModAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.b6ce41.2: %Cpp.long_long.as.ModAssignWith.impl.Op.type.423758.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %ModAssignWith.facet: %ModAssignWith.type.a2e = facet_value %Cpp.long_long, (%ModAssignWith.impl_witness.a7a) [concrete]
-// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.e9d: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%Cpp.long_long, %ModAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.1d8: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.e9d, %ModAssignWith.facet [concrete]
+// CHECK:STDOUT:   %ModAssignWith.facet.9c3: %ModAssignWith.type.a2e = facet_value %Cpp.long_long, (%ModAssignWith.impl_witness.a7a) [concrete]
+// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.e9d: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%Cpp.long_long, %ModAssignWith.facet.9c3) [concrete]
+// CHECK:STDOUT:   %.1d8: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.e9d, %ModAssignWith.facet.9c3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.specific_fn.49870b.1: <specific function> = specific_function %Cpp.long_long.as.ModAssignWith.impl.Op.b6ce41.2, @Cpp.long_long.as.ModAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.specific_fn.49870b.2: <specific function> = specific_function %Cpp.long_long.as.ModAssignWith.impl.Op.b6ce41.1, @Cpp.long_long.as.ModAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %BitAndAssignWith.type.9bc: type = facet_type <@BitAndAssignWith, @BitAndAssignWith(%Cpp.long_long)> [concrete]
@@ -2511,9 +2511,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.492145.1: %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.34c5a7.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.34c5a7.2: type = fn_type @Cpp.long_long.as.BitAndAssignWith.impl.Op.1, @Cpp.long_long.as.BitAndAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.492145.2: %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.34c5a7.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.facet: %BitAndAssignWith.type.9bc = facet_value %Cpp.long_long, (%BitAndAssignWith.impl_witness.a42) [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.8bc: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%Cpp.long_long, %BitAndAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.564: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.8bc, %BitAndAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.facet.c25: %BitAndAssignWith.type.9bc = facet_value %Cpp.long_long, (%BitAndAssignWith.impl_witness.a42) [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.8bc: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%Cpp.long_long, %BitAndAssignWith.facet.c25) [concrete]
+// CHECK:STDOUT:   %.564: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.8bc, %BitAndAssignWith.facet.c25 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.specific_fn.1d5894.1: <specific function> = specific_function %Cpp.long_long.as.BitAndAssignWith.impl.Op.492145.2, @Cpp.long_long.as.BitAndAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.specific_fn.1d5894.2: <specific function> = specific_function %Cpp.long_long.as.BitAndAssignWith.impl.Op.492145.1, @Cpp.long_long.as.BitAndAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %BitOrAssignWith.type.219: type = facet_type <@BitOrAssignWith, @BitOrAssignWith(%Cpp.long_long)> [concrete]
@@ -2526,9 +2526,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.97ef88.1: %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.1655c9.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.1655c9.2: type = fn_type @Cpp.long_long.as.BitOrAssignWith.impl.Op.1, @Cpp.long_long.as.BitOrAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.97ef88.2: %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.1655c9.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.facet: %BitOrAssignWith.type.219 = facet_value %Cpp.long_long, (%BitOrAssignWith.impl_witness.7cf) [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.2ae: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%Cpp.long_long, %BitOrAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.620: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.2ae, %BitOrAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.facet.958: %BitOrAssignWith.type.219 = facet_value %Cpp.long_long, (%BitOrAssignWith.impl_witness.7cf) [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.2ae: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%Cpp.long_long, %BitOrAssignWith.facet.958) [concrete]
+// CHECK:STDOUT:   %.620: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.2ae, %BitOrAssignWith.facet.958 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.specific_fn.76b01d.1: <specific function> = specific_function %Cpp.long_long.as.BitOrAssignWith.impl.Op.97ef88.2, @Cpp.long_long.as.BitOrAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.specific_fn.76b01d.2: <specific function> = specific_function %Cpp.long_long.as.BitOrAssignWith.impl.Op.97ef88.1, @Cpp.long_long.as.BitOrAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %BitXorAssignWith.type.f9d: type = facet_type <@BitXorAssignWith, @BitXorAssignWith(%Cpp.long_long)> [concrete]
@@ -2541,9 +2541,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.60b652.1: %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.42f5ff.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.42f5ff.2: type = fn_type @Cpp.long_long.as.BitXorAssignWith.impl.Op.1, @Cpp.long_long.as.BitXorAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.60b652.2: %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.42f5ff.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.facet: %BitXorAssignWith.type.f9d = facet_value %Cpp.long_long, (%BitXorAssignWith.impl_witness.0ca) [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.af7: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%Cpp.long_long, %BitXorAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.efd: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.af7, %BitXorAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.facet.55f: %BitXorAssignWith.type.f9d = facet_value %Cpp.long_long, (%BitXorAssignWith.impl_witness.0ca) [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.af7: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%Cpp.long_long, %BitXorAssignWith.facet.55f) [concrete]
+// CHECK:STDOUT:   %.efd: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.af7, %BitXorAssignWith.facet.55f [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.specific_fn.960526.1: <specific function> = specific_function %Cpp.long_long.as.BitXorAssignWith.impl.Op.60b652.2, @Cpp.long_long.as.BitXorAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.specific_fn.960526.2: <specific function> = specific_function %Cpp.long_long.as.BitXorAssignWith.impl.Op.60b652.1, @Cpp.long_long.as.BitXorAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %LeftShiftAssignWith.type.f24: type = facet_type <@LeftShiftAssignWith, @LeftShiftAssignWith(%Cpp.long_long)> [concrete]
@@ -2556,9 +2556,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.e0e938.1: %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.c0189e.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.c0189e.2: type = fn_type @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.1, @Cpp.long_long.as.LeftShiftAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.e0e938.2: %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.c0189e.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.facet: %LeftShiftAssignWith.type.f24 = facet_value %Cpp.long_long, (%LeftShiftAssignWith.impl_witness.bee) [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.5d0: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%Cpp.long_long, %LeftShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.ecf: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.5d0, %LeftShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.facet.078: %LeftShiftAssignWith.type.f24 = facet_value %Cpp.long_long, (%LeftShiftAssignWith.impl_witness.bee) [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.5d0: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%Cpp.long_long, %LeftShiftAssignWith.facet.078) [concrete]
+// CHECK:STDOUT:   %.ecf: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.5d0, %LeftShiftAssignWith.facet.078 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.specific_fn.330db6.1: <specific function> = specific_function %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.e0e938.2, @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.specific_fn.330db6.2: <specific function> = specific_function %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.e0e938.1, @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %RightShiftAssignWith.type.42e: type = facet_type <@RightShiftAssignWith, @RightShiftAssignWith(%Cpp.long_long)> [concrete]
@@ -2571,9 +2571,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.60f372.1: %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.440250.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.440250.2: type = fn_type @Cpp.long_long.as.RightShiftAssignWith.impl.Op.1, @Cpp.long_long.as.RightShiftAssignWith.impl(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.60f372.2: %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.440250.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.facet: %RightShiftAssignWith.type.42e = facet_value %Cpp.long_long, (%RightShiftAssignWith.impl_witness.b65) [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.b72: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%Cpp.long_long, %RightShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.580: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.b72, %RightShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.facet.6bd: %RightShiftAssignWith.type.42e = facet_value %Cpp.long_long, (%RightShiftAssignWith.impl_witness.b65) [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.b72: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%Cpp.long_long, %RightShiftAssignWith.facet.6bd) [concrete]
+// CHECK:STDOUT:   %.580: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.b72, %RightShiftAssignWith.facet.6bd [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.specific_fn.e2803d.1: <specific function> = specific_function %Cpp.long_long.as.RightShiftAssignWith.impl.Op.60f372.2, @Cpp.long_long.as.RightShiftAssignWith.impl.Op.1(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.specific_fn.e2803d.2: <specific function> = specific_function %Cpp.long_long.as.RightShiftAssignWith.impl.Op.60f372.1, @Cpp.long_long.as.RightShiftAssignWith.impl.Op.2(%ImplicitAs.facet.73b) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc9_3.2 [concrete]
@@ -2855,9 +2855,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.1: %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.2: type = fn_type @Cpp.long_long.as.AddAssignWith.impl.Op.1, @Cpp.long_long.as.AddAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.2: %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.d84 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.c98) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.9f5: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i64, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.605: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.9f5, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.0dd: %AddAssignWith.type.d84 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.c98) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.9f5: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i64, %AddAssignWith.facet.0dd) [concrete]
+// CHECK:STDOUT:   %.605: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.9f5, %AddAssignWith.facet.0dd [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.47f55f.1: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.2, @Cpp.long_long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.479: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%Cpp.long_long, %ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %.48b: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.479, %ImplicitAs.facet.cee [concrete]
@@ -2874,9 +2874,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.65ca20.1: %Cpp.long_long.as.SubAssignWith.impl.Op.type.e891c3.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.type.e891c3.2: type = fn_type @Cpp.long_long.as.SubAssignWith.impl.Op.1, @Cpp.long_long.as.SubAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.65ca20.2: %Cpp.long_long.as.SubAssignWith.impl.Op.type.e891c3.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %SubAssignWith.facet: %SubAssignWith.type.d66 = facet_value %Cpp.long_long, (%SubAssignWith.impl_witness.230) [concrete]
-// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.f81: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%i64, %SubAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.d45: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.f81, %SubAssignWith.facet [concrete]
+// CHECK:STDOUT:   %SubAssignWith.facet.0cd: %SubAssignWith.type.d66 = facet_value %Cpp.long_long, (%SubAssignWith.impl_witness.230) [concrete]
+// CHECK:STDOUT:   %SubAssignWith.WithSelf.Op.type.f81: type = fn_type @SubAssignWith.WithSelf.Op, @SubAssignWith.WithSelf(%i64, %SubAssignWith.facet.0cd) [concrete]
+// CHECK:STDOUT:   %.d45: type = fn_type_with_self_type %SubAssignWith.WithSelf.Op.type.f81, %SubAssignWith.facet.0cd [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.specific_fn.a1a11e.1: <specific function> = specific_function %Cpp.long_long.as.SubAssignWith.impl.Op.65ca20.2, @Cpp.long_long.as.SubAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.SubAssignWith.impl.Op.specific_fn.a1a11e.2: <specific function> = specific_function %Cpp.long_long.as.SubAssignWith.impl.Op.65ca20.1, @Cpp.long_long.as.SubAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %MulAssignWith.type.e40: type = facet_type <@MulAssignWith, @MulAssignWith(%i64)> [concrete]
@@ -2889,9 +2889,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.407d6d.1: %Cpp.long_long.as.MulAssignWith.impl.Op.type.31c331.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.type.31c331.2: type = fn_type @Cpp.long_long.as.MulAssignWith.impl.Op.1, @Cpp.long_long.as.MulAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.407d6d.2: %Cpp.long_long.as.MulAssignWith.impl.Op.type.31c331.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %MulAssignWith.facet: %MulAssignWith.type.e40 = facet_value %Cpp.long_long, (%MulAssignWith.impl_witness.fd5) [concrete]
-// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.51d: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%i64, %MulAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.a7c: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.51d, %MulAssignWith.facet [concrete]
+// CHECK:STDOUT:   %MulAssignWith.facet.ea8: %MulAssignWith.type.e40 = facet_value %Cpp.long_long, (%MulAssignWith.impl_witness.fd5) [concrete]
+// CHECK:STDOUT:   %MulAssignWith.WithSelf.Op.type.51d: type = fn_type @MulAssignWith.WithSelf.Op, @MulAssignWith.WithSelf(%i64, %MulAssignWith.facet.ea8) [concrete]
+// CHECK:STDOUT:   %.a7c: type = fn_type_with_self_type %MulAssignWith.WithSelf.Op.type.51d, %MulAssignWith.facet.ea8 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.specific_fn.da4954.1: <specific function> = specific_function %Cpp.long_long.as.MulAssignWith.impl.Op.407d6d.2, @Cpp.long_long.as.MulAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.MulAssignWith.impl.Op.specific_fn.da4954.2: <specific function> = specific_function %Cpp.long_long.as.MulAssignWith.impl.Op.407d6d.1, @Cpp.long_long.as.MulAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %DivAssignWith.type.511: type = facet_type <@DivAssignWith, @DivAssignWith(%i64)> [concrete]
@@ -2904,9 +2904,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.5f629f.1: %Cpp.long_long.as.DivAssignWith.impl.Op.type.35f78a.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.type.35f78a.2: type = fn_type @Cpp.long_long.as.DivAssignWith.impl.Op.1, @Cpp.long_long.as.DivAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.5f629f.2: %Cpp.long_long.as.DivAssignWith.impl.Op.type.35f78a.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %DivAssignWith.facet: %DivAssignWith.type.511 = facet_value %Cpp.long_long, (%DivAssignWith.impl_witness.b7a) [concrete]
-// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.a7c: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%i64, %DivAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.9e9: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.a7c, %DivAssignWith.facet [concrete]
+// CHECK:STDOUT:   %DivAssignWith.facet.7c8: %DivAssignWith.type.511 = facet_value %Cpp.long_long, (%DivAssignWith.impl_witness.b7a) [concrete]
+// CHECK:STDOUT:   %DivAssignWith.WithSelf.Op.type.a7c: type = fn_type @DivAssignWith.WithSelf.Op, @DivAssignWith.WithSelf(%i64, %DivAssignWith.facet.7c8) [concrete]
+// CHECK:STDOUT:   %.9e9: type = fn_type_with_self_type %DivAssignWith.WithSelf.Op.type.a7c, %DivAssignWith.facet.7c8 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.specific_fn.b4ca85.1: <specific function> = specific_function %Cpp.long_long.as.DivAssignWith.impl.Op.5f629f.2, @Cpp.long_long.as.DivAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.DivAssignWith.impl.Op.specific_fn.b4ca85.2: <specific function> = specific_function %Cpp.long_long.as.DivAssignWith.impl.Op.5f629f.1, @Cpp.long_long.as.DivAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %ModAssignWith.type.2c3: type = facet_type <@ModAssignWith, @ModAssignWith(%i64)> [concrete]
@@ -2919,9 +2919,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.6cec08.1: %Cpp.long_long.as.ModAssignWith.impl.Op.type.710c53.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.type.710c53.2: type = fn_type @Cpp.long_long.as.ModAssignWith.impl.Op.1, @Cpp.long_long.as.ModAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.6cec08.2: %Cpp.long_long.as.ModAssignWith.impl.Op.type.710c53.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %ModAssignWith.facet: %ModAssignWith.type.2c3 = facet_value %Cpp.long_long, (%ModAssignWith.impl_witness.746) [concrete]
-// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.2ef: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%i64, %ModAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.35e: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.2ef, %ModAssignWith.facet [concrete]
+// CHECK:STDOUT:   %ModAssignWith.facet.9ba: %ModAssignWith.type.2c3 = facet_value %Cpp.long_long, (%ModAssignWith.impl_witness.746) [concrete]
+// CHECK:STDOUT:   %ModAssignWith.WithSelf.Op.type.2ef: type = fn_type @ModAssignWith.WithSelf.Op, @ModAssignWith.WithSelf(%i64, %ModAssignWith.facet.9ba) [concrete]
+// CHECK:STDOUT:   %.35e: type = fn_type_with_self_type %ModAssignWith.WithSelf.Op.type.2ef, %ModAssignWith.facet.9ba [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.specific_fn.49ce9c.1: <specific function> = specific_function %Cpp.long_long.as.ModAssignWith.impl.Op.6cec08.2, @Cpp.long_long.as.ModAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.ModAssignWith.impl.Op.specific_fn.49ce9c.2: <specific function> = specific_function %Cpp.long_long.as.ModAssignWith.impl.Op.6cec08.1, @Cpp.long_long.as.ModAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %BitAndAssignWith.type.8af: type = facet_type <@BitAndAssignWith, @BitAndAssignWith(%i64)> [concrete]
@@ -2934,9 +2934,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.98a24e.1: %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.ef8d37.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.ef8d37.2: type = fn_type @Cpp.long_long.as.BitAndAssignWith.impl.Op.1, @Cpp.long_long.as.BitAndAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.98a24e.2: %Cpp.long_long.as.BitAndAssignWith.impl.Op.type.ef8d37.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.facet: %BitAndAssignWith.type.8af = facet_value %Cpp.long_long, (%BitAndAssignWith.impl_witness.a30) [concrete]
-// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.4de: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%i64, %BitAndAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.6cf: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.4de, %BitAndAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.facet.a43: %BitAndAssignWith.type.8af = facet_value %Cpp.long_long, (%BitAndAssignWith.impl_witness.a30) [concrete]
+// CHECK:STDOUT:   %BitAndAssignWith.WithSelf.Op.type.4de: type = fn_type @BitAndAssignWith.WithSelf.Op, @BitAndAssignWith.WithSelf(%i64, %BitAndAssignWith.facet.a43) [concrete]
+// CHECK:STDOUT:   %.6cf: type = fn_type_with_self_type %BitAndAssignWith.WithSelf.Op.type.4de, %BitAndAssignWith.facet.a43 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.specific_fn.2fa8b1.1: <specific function> = specific_function %Cpp.long_long.as.BitAndAssignWith.impl.Op.98a24e.2, @Cpp.long_long.as.BitAndAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitAndAssignWith.impl.Op.specific_fn.2fa8b1.2: <specific function> = specific_function %Cpp.long_long.as.BitAndAssignWith.impl.Op.98a24e.1, @Cpp.long_long.as.BitAndAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %BitOrAssignWith.type.172: type = facet_type <@BitOrAssignWith, @BitOrAssignWith(%i64)> [concrete]
@@ -2949,9 +2949,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.efcdd8.1: %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.a11270.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.a11270.2: type = fn_type @Cpp.long_long.as.BitOrAssignWith.impl.Op.1, @Cpp.long_long.as.BitOrAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.efcdd8.2: %Cpp.long_long.as.BitOrAssignWith.impl.Op.type.a11270.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.facet: %BitOrAssignWith.type.172 = facet_value %Cpp.long_long, (%BitOrAssignWith.impl_witness.f30) [concrete]
-// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.3d7: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%i64, %BitOrAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.49d: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.3d7, %BitOrAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.facet.6e0: %BitOrAssignWith.type.172 = facet_value %Cpp.long_long, (%BitOrAssignWith.impl_witness.f30) [concrete]
+// CHECK:STDOUT:   %BitOrAssignWith.WithSelf.Op.type.3d7: type = fn_type @BitOrAssignWith.WithSelf.Op, @BitOrAssignWith.WithSelf(%i64, %BitOrAssignWith.facet.6e0) [concrete]
+// CHECK:STDOUT:   %.49d: type = fn_type_with_self_type %BitOrAssignWith.WithSelf.Op.type.3d7, %BitOrAssignWith.facet.6e0 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.specific_fn.bee85f.1: <specific function> = specific_function %Cpp.long_long.as.BitOrAssignWith.impl.Op.efcdd8.2, @Cpp.long_long.as.BitOrAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitOrAssignWith.impl.Op.specific_fn.bee85f.2: <specific function> = specific_function %Cpp.long_long.as.BitOrAssignWith.impl.Op.efcdd8.1, @Cpp.long_long.as.BitOrAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %BitXorAssignWith.type.2c8: type = facet_type <@BitXorAssignWith, @BitXorAssignWith(%i64)> [concrete]
@@ -2964,9 +2964,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.427b1c.1: %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.533a57.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.533a57.2: type = fn_type @Cpp.long_long.as.BitXorAssignWith.impl.Op.1, @Cpp.long_long.as.BitXorAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.427b1c.2: %Cpp.long_long.as.BitXorAssignWith.impl.Op.type.533a57.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.facet: %BitXorAssignWith.type.2c8 = facet_value %Cpp.long_long, (%BitXorAssignWith.impl_witness.637) [concrete]
-// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.b41: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%i64, %BitXorAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.cd3: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.b41, %BitXorAssignWith.facet [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.facet.c45: %BitXorAssignWith.type.2c8 = facet_value %Cpp.long_long, (%BitXorAssignWith.impl_witness.637) [concrete]
+// CHECK:STDOUT:   %BitXorAssignWith.WithSelf.Op.type.b41: type = fn_type @BitXorAssignWith.WithSelf.Op, @BitXorAssignWith.WithSelf(%i64, %BitXorAssignWith.facet.c45) [concrete]
+// CHECK:STDOUT:   %.cd3: type = fn_type_with_self_type %BitXorAssignWith.WithSelf.Op.type.b41, %BitXorAssignWith.facet.c45 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.specific_fn.659754.1: <specific function> = specific_function %Cpp.long_long.as.BitXorAssignWith.impl.Op.427b1c.2, @Cpp.long_long.as.BitXorAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.BitXorAssignWith.impl.Op.specific_fn.659754.2: <specific function> = specific_function %Cpp.long_long.as.BitXorAssignWith.impl.Op.427b1c.1, @Cpp.long_long.as.BitXorAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %LeftShiftAssignWith.type.b97: type = facet_type <@LeftShiftAssignWith, @LeftShiftAssignWith(%i64)> [concrete]
@@ -2979,9 +2979,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.3761f5.1: %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.b8e2a1.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.b8e2a1.2: type = fn_type @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.1, @Cpp.long_long.as.LeftShiftAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.3761f5.2: %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.type.b8e2a1.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.facet: %LeftShiftAssignWith.type.b97 = facet_value %Cpp.long_long, (%LeftShiftAssignWith.impl_witness.cea) [concrete]
-// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.726: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%i64, %LeftShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.90e: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.726, %LeftShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.facet.77c: %LeftShiftAssignWith.type.b97 = facet_value %Cpp.long_long, (%LeftShiftAssignWith.impl_witness.cea) [concrete]
+// CHECK:STDOUT:   %LeftShiftAssignWith.WithSelf.Op.type.726: type = fn_type @LeftShiftAssignWith.WithSelf.Op, @LeftShiftAssignWith.WithSelf(%i64, %LeftShiftAssignWith.facet.77c) [concrete]
+// CHECK:STDOUT:   %.90e: type = fn_type_with_self_type %LeftShiftAssignWith.WithSelf.Op.type.726, %LeftShiftAssignWith.facet.77c [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.specific_fn.ab2c2b.1: <specific function> = specific_function %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.3761f5.2, @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.specific_fn.ab2c2b.2: <specific function> = specific_function %Cpp.long_long.as.LeftShiftAssignWith.impl.Op.3761f5.1, @Cpp.long_long.as.LeftShiftAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %RightShiftAssignWith.type.721: type = facet_type <@RightShiftAssignWith, @RightShiftAssignWith(%i64)> [concrete]
@@ -2994,9 +2994,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.be7a73.1: %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.71dc97.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.71dc97.2: type = fn_type @Cpp.long_long.as.RightShiftAssignWith.impl.Op.1, @Cpp.long_long.as.RightShiftAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.be7a73.2: %Cpp.long_long.as.RightShiftAssignWith.impl.Op.type.71dc97.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.facet: %RightShiftAssignWith.type.721 = facet_value %Cpp.long_long, (%RightShiftAssignWith.impl_witness.cea) [concrete]
-// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.1c1: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%i64, %RightShiftAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.ec8: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.1c1, %RightShiftAssignWith.facet [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.facet.b25: %RightShiftAssignWith.type.721 = facet_value %Cpp.long_long, (%RightShiftAssignWith.impl_witness.cea) [concrete]
+// CHECK:STDOUT:   %RightShiftAssignWith.WithSelf.Op.type.1c1: type = fn_type @RightShiftAssignWith.WithSelf.Op, @RightShiftAssignWith.WithSelf(%i64, %RightShiftAssignWith.facet.b25) [concrete]
+// CHECK:STDOUT:   %.ec8: type = fn_type_with_self_type %RightShiftAssignWith.WithSelf.Op.type.1c1, %RightShiftAssignWith.facet.b25 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.specific_fn.3074f6.1: <specific function> = specific_function %Cpp.long_long.as.RightShiftAssignWith.impl.Op.be7a73.2, @Cpp.long_long.as.RightShiftAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.RightShiftAssignWith.impl.Op.specific_fn.3074f6.2: <specific function> = specific_function %Cpp.long_long.as.RightShiftAssignWith.impl.Op.be7a73.1, @Cpp.long_long.as.RightShiftAssignWith.impl.Op.2(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc9_3.2 [concrete]
@@ -3344,9 +3344,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.65d685.1: %Cpp.long_long.as.AddAssignWith.impl.Op.type.9da307.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.type.9da307.2: type = fn_type @Cpp.long_long.as.AddAssignWith.impl.Op.1, @Cpp.long_long.as.AddAssignWith.impl(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.65d685.2: %Cpp.long_long.as.AddAssignWith.impl.Op.type.9da307.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.761 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.d24) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.4c6: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(Core.IntLiteral, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.2d5: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.4c6, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.fc3: %AddAssignWith.type.761 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.d24) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.4c6: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(Core.IntLiteral, %AddAssignWith.facet.fc3) [concrete]
+// CHECK:STDOUT:   %.2d5: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.4c6, %AddAssignWith.facet.fc3 [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.616d71.1: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.65d685.2, @Cpp.long_long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.616d71.2: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.65d685.1, @Cpp.long_long.as.AddAssignWith.impl.Op.2(%ImplicitAs.facet) [concrete]
 // CHECK:STDOUT:   %Destroy.Op.type.bae255.2: type = fn_type @Destroy.Op.loc8_3.2 [concrete]
@@ -3466,9 +3466,9 @@ fn CopyUnsignedLongLong() {
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.1: %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.1 = struct_value () [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.2: type = fn_type @Cpp.long_long.as.AddAssignWith.impl.Op.1, @Cpp.long_long.as.AddAssignWith.impl(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.2: %Cpp.long_long.as.AddAssignWith.impl.Op.type.61f9d4.2 = struct_value () [concrete]
-// CHECK:STDOUT:   %AddAssignWith.facet: %AddAssignWith.type.d84 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.c98) [concrete]
-// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.9f5: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i64, %AddAssignWith.facet) [concrete]
-// CHECK:STDOUT:   %.605: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.9f5, %AddAssignWith.facet [concrete]
+// CHECK:STDOUT:   %AddAssignWith.facet.0dd: %AddAssignWith.type.d84 = facet_value %Cpp.long_long, (%AddAssignWith.impl_witness.c98) [concrete]
+// CHECK:STDOUT:   %AddAssignWith.WithSelf.Op.type.9f5: type = fn_type @AddAssignWith.WithSelf.Op, @AddAssignWith.WithSelf(%i64, %AddAssignWith.facet.0dd) [concrete]
+// CHECK:STDOUT:   %.605: type = fn_type_with_self_type %AddAssignWith.WithSelf.Op.type.9f5, %AddAssignWith.facet.0dd [concrete]
 // CHECK:STDOUT:   %Cpp.long_long.as.AddAssignWith.impl.Op.specific_fn.47f55f.1: <specific function> = specific_function %Cpp.long_long.as.AddAssignWith.impl.Op.3aaab8.2, @Cpp.long_long.as.AddAssignWith.impl.Op.1(%ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.479: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%Cpp.long_long, %ImplicitAs.facet.cee) [concrete]
 // CHECK:STDOUT:   %.48b: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.479, %ImplicitAs.facet.cee [concrete]
diff --git a/toolchain/check/testdata/interop/cpp/primitive_types/void_pointer.carbon b/toolchain/check/testdata/interop/cpp/primitive_types/void_pointer.carbon
index a5bb88632c91..7e4d8ca01a1f 100644
--- a/toolchain/check/testdata/interop/cpp/primitive_types/void_pointer.carbon
+++ b/toolchain/check/testdata/interop/cpp/primitive_types/void_pointer.carbon
@@ -151,9 +151,9 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ImplicitAs.impl_witness.429: <witness> = impl_witness imports.%ImplicitAs.impl_witness_table.e02, @ptr.as.ImplicitAs.impl.1b5(%S) [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.type.31c: type = fn_type @ptr.as.ImplicitAs.impl.Convert.1, @ptr.as.ImplicitAs.impl.1b5(%S) [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.b9d: %ptr.as.ImplicitAs.impl.Convert.type.31c = struct_value () [concrete]
-// CHECK:STDOUT:   %ImplicitAs.facet: %ImplicitAs.type.02d = facet_value %ptr.5c7, (%ImplicitAs.impl_witness.429) [concrete]
-// CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.068: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%ptr.874, %ImplicitAs.facet) [concrete]
-// CHECK:STDOUT:   %.d36: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.068, %ImplicitAs.facet [concrete]
+// CHECK:STDOUT:   %ImplicitAs.facet.ed7: %ImplicitAs.type.02d = facet_value %ptr.5c7, (%ImplicitAs.impl_witness.429) [concrete]
+// CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.068: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%ptr.874, %ImplicitAs.facet.ed7) [concrete]
+// CHECK:STDOUT:   %.d36: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.068, %ImplicitAs.facet.ed7 [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.specific_fn.9f6: <specific function> = specific_function %ptr.as.ImplicitAs.impl.Convert.b9d, @ptr.as.ImplicitAs.impl.Convert.1(%S) [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -205,9 +205,9 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ImplicitAs.impl_witness.f70: <witness> = impl_witness imports.%ImplicitAs.impl_witness_table.e02, @ptr.as.ImplicitAs.impl.1b5(%C) [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.type.791: type = fn_type @ptr.as.ImplicitAs.impl.Convert.1, @ptr.as.ImplicitAs.impl.1b5(%C) [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.af8: %ptr.as.ImplicitAs.impl.Convert.type.791 = struct_value () [concrete]
-// CHECK:STDOUT:   %ImplicitAs.facet: %ImplicitAs.type.02d = facet_value %ptr.31e, (%ImplicitAs.impl_witness.f70) [concrete]
-// CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.1e1: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%ptr.874, %ImplicitAs.facet) [concrete]
-// CHECK:STDOUT:   %.41e: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.1e1, %ImplicitAs.facet [concrete]
+// CHECK:STDOUT:   %ImplicitAs.facet.bcb: %ImplicitAs.type.02d = facet_value %ptr.31e, (%ImplicitAs.impl_witness.f70) [concrete]
+// CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.type.1e1: type = fn_type @ImplicitAs.WithSelf.Convert, @ImplicitAs.WithSelf(%ptr.874, %ImplicitAs.facet.bcb) [concrete]
+// CHECK:STDOUT:   %.41e: type = fn_type_with_self_type %ImplicitAs.WithSelf.Convert.type.1e1, %ImplicitAs.facet.bcb [concrete]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.specific_fn.a56: <specific function> = specific_function %ptr.as.ImplicitAs.impl.Convert.af8, @ptr.as.ImplicitAs.impl.Convert.1(%C) [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -261,14 +261,14 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.type.502: type = fn_type @ptr.as.ImplicitAs.impl.Convert.1, @ptr.as.ImplicitAs.impl.1b5(%T.67d) [symbolic]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.02e: %ptr.as.ImplicitAs.impl.Convert.type.502 = struct_value () [symbolic]
 // CHECK:STDOUT:   %ImplicitAs.impl_witness.429: <witness> = impl_witness imports.%ImplicitAs.impl_witness_table.e02, @ptr.as.ImplicitAs.impl.1b5(%S) [concrete]
-// CHECK:STDOUT:   %ImplicitAs.facet: %ImplicitAs.type.02d = facet_value %ptr.5c7, (%ImplicitAs.impl_witness.429) [concrete]
-// CHECK:STDOUT:   %As.impl_witness.58f: <witness> = impl_witness imports.%As.impl_witness_table.0dc, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet) [concrete]
-// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.type.d89: type = fn_type @T.as_type.as.As.impl.Convert, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet) [concrete]
+// CHECK:STDOUT:   %ImplicitAs.facet.ed7: %ImplicitAs.type.02d = facet_value %ptr.5c7, (%ImplicitAs.impl_witness.429) [concrete]
+// CHECK:STDOUT:   %As.impl_witness.58f: <witness> = impl_witness imports.%As.impl_witness_table.0dc, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet.ed7) [concrete]
+// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.type.d89: type = fn_type @T.as_type.as.As.impl.Convert, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet.ed7) [concrete]
 // CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.e8b: %T.as_type.as.As.impl.Convert.type.d89 = struct_value () [concrete]
 // CHECK:STDOUT:   %As.facet: %As.type.d24 = facet_value %ptr.5c7, (%As.impl_witness.58f) [concrete]
 // CHECK:STDOUT:   %As.WithSelf.Convert.type.2d8: type = fn_type @As.WithSelf.Convert, @As.WithSelf(%ptr.874, %As.facet) [concrete]
 // CHECK:STDOUT:   %.187: type = fn_type_with_self_type %As.WithSelf.Convert.type.2d8, %As.facet [concrete]
-// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.specific_fn: <specific function> = specific_function %T.as_type.as.As.impl.Convert.e8b, @T.as_type.as.As.impl.Convert(%ptr.874, %ImplicitAs.facet) [concrete]
+// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.specific_fn: <specific function> = specific_function %T.as_type.as.As.impl.Convert.e8b, @T.as_type.as.As.impl.Convert(%ptr.874, %ImplicitAs.facet.ed7) [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -295,7 +295,7 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ptr.loc10_46: type = ptr_type %void.ref.loc10_41 [concrete = constants.%ptr.874]
 // CHECK:STDOUT:   %impl.elem0: %.187 = impl_witness_access constants.%As.impl_witness.58f, element0 [concrete = constants.%T.as_type.as.As.impl.Convert.e8b]
 // CHECK:STDOUT:   %bound_method.loc10_35.1: <bound method> = bound_method %input.ref, %impl.elem0
-// CHECK:STDOUT:   %specific_fn: <specific function> = specific_function %impl.elem0, @T.as_type.as.As.impl.Convert(constants.%ptr.874, constants.%ImplicitAs.facet) [concrete = constants.%T.as_type.as.As.impl.Convert.specific_fn]
+// CHECK:STDOUT:   %specific_fn: <specific function> = specific_function %impl.elem0, @T.as_type.as.As.impl.Convert(constants.%ptr.874, constants.%ImplicitAs.facet.ed7) [concrete = constants.%T.as_type.as.As.impl.Convert.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc10_35.2: <bound method> = bound_method %input.ref, %specific_fn
 // CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.call: init %ptr.874 = call %bound_method.loc10_35.2(%input.ref)
 // CHECK:STDOUT:   %.loc10_35.1: %ptr.874 = value_of_initializer %T.as_type.as.As.impl.Convert.call
@@ -328,14 +328,14 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.type.502: type = fn_type @ptr.as.ImplicitAs.impl.Convert.1, @ptr.as.ImplicitAs.impl.1b5(%T.67d) [symbolic]
 // CHECK:STDOUT:   %ptr.as.ImplicitAs.impl.Convert.02e: %ptr.as.ImplicitAs.impl.Convert.type.502 = struct_value () [symbolic]
 // CHECK:STDOUT:   %ImplicitAs.impl_witness.f70: <witness> = impl_witness imports.%ImplicitAs.impl_witness_table.e02, @ptr.as.ImplicitAs.impl.1b5(%C) [concrete]
-// CHECK:STDOUT:   %ImplicitAs.facet: %ImplicitAs.type.02d = facet_value %ptr.31e, (%ImplicitAs.impl_witness.f70) [concrete]
-// CHECK:STDOUT:   %As.impl_witness.a9a: <witness> = impl_witness imports.%As.impl_witness_table.0dc, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet) [concrete]
-// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.type.758: type = fn_type @T.as_type.as.As.impl.Convert, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet) [concrete]
+// CHECK:STDOUT:   %ImplicitAs.facet.bcb: %ImplicitAs.type.02d = facet_value %ptr.31e, (%ImplicitAs.impl_witness.f70) [concrete]
+// CHECK:STDOUT:   %As.impl_witness.a9a: <witness> = impl_witness imports.%As.impl_witness_table.0dc, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet.bcb) [concrete]
+// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.type.758: type = fn_type @T.as_type.as.As.impl.Convert, @T.as_type.as.As.impl(%ptr.874, %ImplicitAs.facet.bcb) [concrete]
 // CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.57a: %T.as_type.as.As.impl.Convert.type.758 = struct_value () [concrete]
 // CHECK:STDOUT:   %As.facet: %As.type.d24 = facet_value %ptr.31e, (%As.impl_witness.a9a) [concrete]
 // CHECK:STDOUT:   %As.WithSelf.Convert.type.dc8: type = fn_type @As.WithSelf.Convert, @As.WithSelf(%ptr.874, %As.facet) [concrete]
 // CHECK:STDOUT:   %.85e: type = fn_type_with_self_type %As.WithSelf.Convert.type.dc8, %As.facet [concrete]
-// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.specific_fn: <specific function> = specific_function %T.as_type.as.As.impl.Convert.57a, @T.as_type.as.As.impl.Convert(%ptr.874, %ImplicitAs.facet) [concrete]
+// CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.specific_fn: <specific function> = specific_function %T.as_type.as.As.impl.Convert.57a, @T.as_type.as.As.impl.Convert(%ptr.874, %ImplicitAs.facet.bcb) [concrete]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -360,7 +360,7 @@ fn F(input: Cpp.void*) {
 // CHECK:STDOUT:   %ptr.loc10_46: type = ptr_type %void.ref.loc10_41 [concrete = constants.%ptr.874]
 // CHECK:STDOUT:   %impl.elem0: %.85e = impl_witness_access constants.%As.impl_witness.a9a, element0 [concrete = constants.%T.as_type.as.As.impl.Convert.57a]
 // CHECK:STDOUT:   %bound_method.loc10_35.1: <bound method> = bound_method %input.ref, %impl.elem0
-// CHECK:STDOUT:   %specific_fn: <specific function> = specific_function %impl.elem0, @T.as_type.as.As.impl.Convert(constants.%ptr.874, constants.%ImplicitAs.facet) [concrete = constants.%T.as_type.as.As.impl.Convert.specific_fn]
+// CHECK:STDOUT:   %specific_fn: <specific function> = specific_function %impl.elem0, @T.as_type.as.As.impl.Convert(constants.%ptr.874, constants.%ImplicitAs.facet.bcb) [concrete = constants.%T.as_type.as.As.impl.Convert.specific_fn]
 // CHECK:STDOUT:   %bound_method.loc10_35.2: <bound method> = bound_method %input.ref, %specific_fn
 // CHECK:STDOUT:   %T.as_type.as.As.impl.Convert.call: init %ptr.874 = call %bound_method.loc10_35.2(%input.ref)
 // CHECK:STDOUT:   %.loc10_35.1: %ptr.874 = value_of_initializer %T.as_type.as.As.impl.Convert.call
diff --git a/toolchain/check/thunk.cpp b/toolchain/check/thunk.cpp
index 2eaf74e0fdef..0f3cd074a2c5 100644
--- a/toolchain/check/thunk.cpp
+++ b/toolchain/check/thunk.cpp
@@ -29,6 +29,7 @@
 #include "toolchain/sem_ir/ids.h"
 #include "toolchain/sem_ir/inst.h"
 #include "toolchain/sem_ir/pattern.h"
+#include "toolchain/sem_ir/thunk.h"
 #include "toolchain/sem_ir/typed_insts.h"
 
 namespace Carbon::Check {
@@ -489,12 +490,17 @@ auto BuildThunk(Context& context, SemIR::FunctionId signature_id,
   // We can't use the function directly. Build a thunk.
   // TODO: Check for and diagnose obvious reasons why this will fail, such as
   // arity mismatch, before trying to build the thunk.
-  auto [function_id, thunk_id] =
+  auto [function_id, thunk_inst_id] =
       CloneFunctionDecl(context, SemIR::LocId(callee_id), signature_id,
                         signature_specific_id, callee.function_id);
 
+  auto thunk_id =
+      context.sem_ir().thunks().Add({.callee_id = callee_id,
+                                     .signature_id = signature_id,
+                                     .specific_id = signature_specific_id});
+
   // Track that this function is a thunk.
-  context.functions().Get(function_id).SetThunk(callee_id);
+  context.functions().Get(function_id).SetThunk(thunk_id);
 
   if (defer_definition) {
     // Register the thunk to be defined when we reach the end of the enclosing
@@ -504,16 +510,16 @@ auto BuildThunk(Context& context, SemIR::FunctionId signature_id,
         context, {
                      .signature_id = signature_id,
                      .function_id = function_id,
-                     .decl_id = thunk_id,
+                     .decl_id = thunk_inst_id,
                      .callee_id = callee_id,
                  });
   } else {
-    BuildThunkDefinition(context, signature_id, function_id, thunk_id,
+    BuildThunkDefinition(context, signature_id, function_id, thunk_inst_id,
                          callee_id);
     context.scope_stack().Pop();
   }
 
-  return thunk_id;
+  return thunk_inst_id;
 }
 
 auto BuildDestroyThunk(Context& context, SemIR::LocId loc_id,
@@ -528,7 +534,7 @@ auto BuildDestroyThunk(Context& context, SemIR::LocId loc_id,
                                  .self_type_id = class_info.self_type_id});
 
   auto& thunk_function = context.functions().Get(thunk_function_id);
-  thunk_function.SetThunk(SemIR::InstId::None);
+  thunk_function.SetThunk(SemIR::ThunkId::None);
 
   context.scope_stack().PushForDeclName();
   StartFunctionDefinition(context, thunk_inst_id, thunk_function_id);
diff --git a/toolchain/driver/testdata/compile/optimize/optimize_debug.carbon b/toolchain/driver/testdata/compile/optimize/optimize_debug.carbon
index 5d6e4733505b..3521693bb873 100644
--- a/toolchain/driver/testdata/compile/optimize/optimize_debug.carbon
+++ b/toolchain/driver/testdata/compile/optimize/optimize_debug.carbon
@@ -120,7 +120,7 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT: !22 = !DILocation(line: 18, column: 9, scope: !16)
 // CHECK:STDOUT: !23 = !DILocation(line: 19, column: 5, scope: !16)
 // CHECK:STDOUT: !24 = !DILocation(line: 299, column: 3, scope: !25, inlinedAt: !32)
-// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !26, line: 299, type: !27, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !29)
+// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !26, line: 299, type: !27, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !29)
 // CHECK:STDOUT: !26 = !DIFile(filename: "{{.*}}/prelude/types/int.carbon", directory: "")
 // CHECK:STDOUT: !27 = !DISubroutineType(types: !28)
 // CHECK:STDOUT: !28 = !{null, !7, !7}
diff --git a/toolchain/driver/testdata/compile/optimize/optimize_default.carbon b/toolchain/driver/testdata/compile/optimize/optimize_default.carbon
index fa27740bdc78..d2734013eb1a 100644
--- a/toolchain/driver/testdata/compile/optimize/optimize_default.carbon
+++ b/toolchain/driver/testdata/compile/optimize/optimize_default.carbon
@@ -120,7 +120,7 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT: !22 = !DILocation(line: 18, column: 9, scope: !16)
 // CHECK:STDOUT: !23 = !DILocation(line: 19, column: 5, scope: !16)
 // CHECK:STDOUT: !24 = !DILocation(line: 299, column: 3, scope: !25, inlinedAt: !32)
-// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !26, line: 299, type: !27, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !29)
+// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !26, line: 299, type: !27, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !29)
 // CHECK:STDOUT: !26 = !DIFile(filename: "{{.*}}/prelude/types/int.carbon", directory: "")
 // CHECK:STDOUT: !27 = !DISubroutineType(types: !28)
 // CHECK:STDOUT: !28 = !{null, !7, !7}
diff --git a/toolchain/driver/testdata/compile/optimize/optimize_none.carbon b/toolchain/driver/testdata/compile/optimize/optimize_none.carbon
index 4a4a28a96b24..25998d1b6a19 100644
--- a/toolchain/driver/testdata/compile/optimize/optimize_none.carbon
+++ b/toolchain/driver/testdata/compile/optimize/optimize_none.carbon
@@ -94,12 +94,12 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: noinline nounwind optnone
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !34 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !38
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !38
 // CHECK:STDOUT:   ret void, !dbg !39
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: noinline nounwind optnone
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #0 !dbg !40 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #0 !dbg !40 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.1f02987e9673cc00:ImplicitAs.d993a5132e000405.Core.dc9462e6da0d394c"(i32 %other), !dbg !46
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !47
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !47
@@ -164,7 +164,7 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT: !37 = !DILocalVariable(arg: 1, scope: !34, type: !7)
 // CHECK:STDOUT: !38 = !DILocation(line: 365, column: 5, scope: !34)
 // CHECK:STDOUT: !39 = !DILocation(line: 363, column: 3, scope: !34)
-// CHECK:STDOUT: !40 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !35, line: 299, type: !41, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !43)
+// CHECK:STDOUT: !40 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !35, line: 299, type: !41, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !43)
 // CHECK:STDOUT: !41 = !DISubroutineType(types: !42)
 // CHECK:STDOUT: !42 = !{null, !7, !7}
 // CHECK:STDOUT: !43 = !{!44, !45}
diff --git a/toolchain/driver/testdata/compile/optimize/optimize_size.carbon b/toolchain/driver/testdata/compile/optimize/optimize_size.carbon
index 26b2597759c3..d686abf669fb 100644
--- a/toolchain/driver/testdata/compile/optimize/optimize_size.carbon
+++ b/toolchain/driver/testdata/compile/optimize/optimize_size.carbon
@@ -93,12 +93,12 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: minsize nounwind optsize
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !34 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !38
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !38
 // CHECK:STDOUT:   ret void, !dbg !39
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline minsize nounwind optsize
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !40 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !40 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.1f02987e9673cc00:ImplicitAs.d993a5132e000405.Core.dc9462e6da0d394c"(i32 %other), !dbg !46
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !47
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !47
@@ -164,7 +164,7 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT: !37 = !DILocalVariable(arg: 1, scope: !34, type: !7)
 // CHECK:STDOUT: !38 = !DILocation(line: 365, column: 5, scope: !34)
 // CHECK:STDOUT: !39 = !DILocation(line: 363, column: 3, scope: !34)
-// CHECK:STDOUT: !40 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !35, line: 299, type: !41, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !43)
+// CHECK:STDOUT: !40 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !35, line: 299, type: !41, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !43)
 // CHECK:STDOUT: !41 = !DISubroutineType(types: !42)
 // CHECK:STDOUT: !42 = !{null, !7, !7}
 // CHECK:STDOUT: !43 = !{!44, !45}
diff --git a/toolchain/driver/testdata/compile/optimize/optimize_speed.carbon b/toolchain/driver/testdata/compile/optimize/optimize_speed.carbon
index c42331260842..bbef64c7f374 100644
--- a/toolchain/driver/testdata/compile/optimize/optimize_speed.carbon
+++ b/toolchain/driver/testdata/compile/optimize/optimize_speed.carbon
@@ -135,7 +135,7 @@ fn VectorizedWithOptSpeed(a: array(i32, 65536)*) {
 // CHECK:STDOUT: !21 = !DILocalVariable(arg: 1, scope: !16, type: !19)
 // CHECK:STDOUT: !22 = !DILocation(line: 18, column: 9, scope: !16)
 // CHECK:STDOUT: !23 = !DILocation(line: 299, column: 3, scope: !24, inlinedAt: !31)
-// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !25, line: 299, type: !26, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !28)
+// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !25, line: 299, type: !26, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !28)
 // CHECK:STDOUT: !25 = !DIFile(filename: "{{.*}}/prelude/types/int.carbon", directory: "")
 // CHECK:STDOUT: !26 = !DISubroutineType(types: !27)
 // CHECK:STDOUT: !27 = !{null, !7, !7}
diff --git a/toolchain/lower/testdata/array/iterate.carbon b/toolchain/lower/testdata/array/iterate.carbon
index 4da5a4ba1525..2c21103febc4 100644
--- a/toolchain/lower/testdata/array/iterate.carbon
+++ b/toolchain/lower/testdata/array/iterate.carbon
@@ -141,7 +141,7 @@ fn F() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !77 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b"(ptr %self, i32 1), !dbg !81
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.37e622b8bcf1ddff.Core:Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b"(ptr %self, i32 1), !dbg !81
 // CHECK:STDOUT:   ret void, !dbg !82
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -173,7 +173,7 @@ fn F() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b"(ptr %self, i32 %other) #2 !dbg !105 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.37e622b8bcf1ddff.Core:Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b"(ptr %self, i32 %other) #2 !dbg !105 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.0b8d6a4f60e9338d:ImplicitAs.11da3bb3c3dce533.Core.fe879877fb5b368f"(i32 %other), !dbg !111
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !112
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !112
@@ -323,7 +323,7 @@ fn F() {
 // CHECK:STDOUT: !102 = !DILocalVariable(arg: 1, scope: !100, type: !26)
 // CHECK:STDOUT: !103 = !DILocation(line: 136, column: 12, scope: !100)
 // CHECK:STDOUT: !104 = !DILocation(line: 136, column: 5, scope: !100)
-// CHECK:STDOUT: !105 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b", scope: null, file: !78, line: 299, type: !106, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !108)
+// CHECK:STDOUT: !105 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.37e622b8bcf1ddff.Core:Int.9452f4c51951679b.Core:AddAssignWith.3fed4bf7a4851faa.Core.5c85b74322e1187b", scope: null, file: !78, line: 299, type: !106, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !108)
 // CHECK:STDOUT: !106 = !DISubroutineType(types: !107)
 // CHECK:STDOUT: !107 = !{null, !15, !15}
 // CHECK:STDOUT: !108 = !{!109, !110}
diff --git a/toolchain/lower/testdata/for/break_continue.carbon b/toolchain/lower/testdata/for/break_continue.carbon
index 681058deb200..c6a87e1230bb 100644
--- a/toolchain/lower/testdata/for/break_continue.carbon
+++ b/toolchain/lower/testdata/for/break_continue.carbon
@@ -173,7 +173,7 @@ fn For() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !90 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !94
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !94
 // CHECK:STDOUT:   ret void, !dbg !95
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -205,7 +205,7 @@ fn For() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !118 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !118 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.1f02987e9673cc00:ImplicitAs.d993a5132e000405.Core.dc9462e6da0d394c"(i32 %other), !dbg !124
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !125
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !125
@@ -368,7 +368,7 @@ fn For() {
 // CHECK:STDOUT: !115 = !DILocalVariable(arg: 1, scope: !113, type: !33)
 // CHECK:STDOUT: !116 = !DILocation(line: 136, column: 12, scope: !113)
 // CHECK:STDOUT: !117 = !DILocation(line: 136, column: 5, scope: !113)
-// CHECK:STDOUT: !118 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !91, line: 299, type: !119, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !121)
+// CHECK:STDOUT: !118 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !91, line: 299, type: !119, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !121)
 // CHECK:STDOUT: !119 = !DISubroutineType(types: !120)
 // CHECK:STDOUT: !120 = !{null, !22, !22}
 // CHECK:STDOUT: !121 = !{!122, !123}
diff --git a/toolchain/lower/testdata/for/for.carbon b/toolchain/lower/testdata/for/for.carbon
index 26a86d814b65..c2054d75d7e1 100644
--- a/toolchain/lower/testdata/for/for.carbon
+++ b/toolchain/lower/testdata/for/for.carbon
@@ -161,7 +161,7 @@ fn For() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !86 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !90
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !90
 // CHECK:STDOUT:   ret void, !dbg !91
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -193,7 +193,7 @@ fn For() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !114 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !114 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.1f02987e9673cc00:ImplicitAs.d993a5132e000405.Core.dc9462e6da0d394c"(i32 %other), !dbg !120
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !121
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !121
@@ -352,7 +352,7 @@ fn For() {
 // CHECK:STDOUT: !111 = !DILocalVariable(arg: 1, scope: !109, type: !29)
 // CHECK:STDOUT: !112 = !DILocation(line: 136, column: 12, scope: !109)
 // CHECK:STDOUT: !113 = !DILocation(line: 136, column: 5, scope: !109)
-// CHECK:STDOUT: !114 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !87, line: 299, type: !115, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !117)
+// CHECK:STDOUT: !114 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.848b00090916d4a0.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !87, line: 299, type: !115, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !117)
 // CHECK:STDOUT: !115 = !DISubroutineType(types: !116)
 // CHECK:STDOUT: !116 = !{null, !18, !18}
 // CHECK:STDOUT: !117 = !{!118, !119}
diff --git a/toolchain/lower/testdata/impl/import_thunk.carbon b/toolchain/lower/testdata/impl/import_thunk.carbon
index 4469e120cea2..18fbd41d296e 100644
--- a/toolchain/lower/testdata/impl/import_thunk.carbon
+++ b/toolchain/lower/testdata/impl/import_thunk.carbon
@@ -100,7 +100,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_CF:thunk.61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
+// CHECK:STDOUT: define void @"_CF:thunk:I.5ae44f439e6b6107.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %.loc20_19.1.temp = alloca { i32 }, align 8, !dbg !28
 // CHECK:STDOUT:   %.loc16_9.1.temp = alloca { i32 }, align 8, !dbg !29
@@ -171,7 +171,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT: !22 = !DILocation(line: 20, column: 34, scope: !19)
 // CHECK:STDOUT: !23 = !DILocation(line: 20, column: 28, scope: !19)
 // CHECK:STDOUT: !24 = !DILocation(line: 20, column: 21, scope: !19)
-// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk.61ea2aba74ab3bf1:I.Main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
+// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk:I.5ae44f439e6b6107.Main:61ea2aba74ab3bf1:I.Main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
 // CHECK:STDOUT: !26 = !{!27}
 // CHECK:STDOUT: !27 = !DILocalVariable(arg: 1, scope: !25, type: !7)
 // CHECK:STDOUT: !28 = !DILocation(line: 20, column: 3, scope: !25)
@@ -213,7 +213,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT:   ret void, !dbg !12
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: declare void @"_CF:thunk.61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }), ptr)
+// CHECK:STDOUT: declare void @"_CF:thunk:I.1ede6ff4110118d7.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }), ptr)
 // CHECK:STDOUT:
 // CHECK:STDOUT: declare void @"_CF.61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }), ptr)
 // CHECK:STDOUT:
@@ -296,7 +296,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_CF:thunk.X.Main:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !13 {
+// CHECK:STDOUT: define void @"_CF:thunk:I.e55c78367db83a6b.Main:X.Main:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !13 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %.loc9_19.1.temp = alloca { i32 }, align 8, !dbg !16
 // CHECK:STDOUT:   %.2.temp = alloca { i32 }, align 8
@@ -359,7 +359,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT: !10 = !DILocation(line: 9, column: 34, scope: !4)
 // CHECK:STDOUT: !11 = !DILocation(line: 9, column: 28, scope: !4)
 // CHECK:STDOUT: !12 = !DILocation(line: 9, column: 21, scope: !4)
-// CHECK:STDOUT: !13 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk.X.Main:I.Main", scope: null, file: !3, line: 9, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !14)
+// CHECK:STDOUT: !13 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk:I.e55c78367db83a6b.Main:X.Main:I.Main", scope: null, file: !3, line: 9, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !14)
 // CHECK:STDOUT: !14 = !{!15}
 // CHECK:STDOUT: !15 = !DILocalVariable(arg: 1, scope: !13, type: !7)
 // CHECK:STDOUT: !16 = !DILocation(line: 9, column: 3, scope: !13)
@@ -401,7 +401,7 @@ fn Test(a: A) -> C {
 // CHECK:STDOUT:   ret void, !dbg !12
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
-// CHECK:STDOUT: declare void @"_CF:thunk.X.Main:I.Main"(ptr sret({ i32 }), ptr)
+// CHECK:STDOUT: declare void @"_CF:thunk:I.9d1db36de5cccc48.Main:X.Main:I.Main"(ptr sret({ i32 }), ptr)
 // CHECK:STDOUT:
 // CHECK:STDOUT: declare void @"_CF.X.Main:I.Main"(ptr sret({ i32 }), ptr)
 // CHECK:STDOUT:
diff --git a/toolchain/lower/testdata/impl/thunk.carbon b/toolchain/lower/testdata/impl/thunk.carbon
index 63eada751a61..e36a8be8a730 100644
--- a/toolchain/lower/testdata/impl/thunk.carbon
+++ b/toolchain/lower/testdata/impl/thunk.carbon
@@ -104,7 +104,7 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_CF:thunk.61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
+// CHECK:STDOUT: define void @"_CF:thunk:I.5ae44f439e6b6107.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %.loc20_19.1.temp = alloca { i32 }, align 8, !dbg !28
 // CHECK:STDOUT:   %.loc16_9.1.temp = alloca { i32 }, align 8, !dbg !29
@@ -192,7 +192,7 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
 // CHECK:STDOUT: !22 = !DILocation(line: 20, column: 34, scope: !19)
 // CHECK:STDOUT: !23 = !DILocation(line: 20, column: 28, scope: !19)
 // CHECK:STDOUT: !24 = !DILocation(line: 20, column: 21, scope: !19)
-// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk.61ea2aba74ab3bf1:I.Main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
+// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk:I.5ae44f439e6b6107.Main:61ea2aba74ab3bf1:I.Main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
 // CHECK:STDOUT: !26 = !{!27}
 // CHECK:STDOUT: !27 = !DILocalVariable(arg: 1, scope: !25, type: !7)
 // CHECK:STDOUT: !28 = !DILocation(line: 20, column: 3, scope: !25)
@@ -289,12 +289,12 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @_CCallGeneric.Main.0bac38e8a17f7a1f(ptr sret({}) %return, ptr %c, ptr %b) #0 !dbg !41 {
 // CHECK:STDOUT: entry:
-// CHECK:STDOUT:   call void @"_CF:thunk.C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f"(ptr %return, ptr %c, ptr %b), !dbg !45
+// CHECK:STDOUT:   call void @"_CF:thunk:I.1f5037c5d69ffaf4.Main:C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f"(ptr %return, ptr %c, ptr %b), !dbg !45
 // CHECK:STDOUT:   ret void, !dbg !46
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_CF:thunk.C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f"(ptr sret({}) %return, ptr %self, ptr %x) #3 !dbg !47 {
+// CHECK:STDOUT: define linkonce_odr void @"_CF:thunk:I.1f5037c5d69ffaf4.Main:C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f"(ptr sret({}) %return, ptr %self, ptr %x) #3 !dbg !47 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   %.loc18_38.2.temp = alloca {}, align 8, !dbg !51
 // CHECK:STDOUT:   %.loc18_38.6.temp = alloca {}, align 8, !dbg !51
@@ -370,7 +370,7 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
 // CHECK:STDOUT: !44 = !DILocalVariable(arg: 2, scope: !41, type: !7)
 // CHECK:STDOUT: !45 = !DILocation(line: 26, column: 10, scope: !41)
 // CHECK:STDOUT: !46 = !DILocation(line: 26, column: 3, scope: !41)
-// CHECK:STDOUT: !47 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk.C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f", scope: null, file: !3, line: 18, type: !22, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !48)
+// CHECK:STDOUT: !47 = distinct !DISubprogram(name: "F", linkageName: "_CF:thunk:I.1f5037c5d69ffaf4.Main:C.eb057aa32837c84e.Main:I.eb057aa32837c84e.Main.e43630e9a6c38c3f", scope: null, file: !3, line: 18, type: !22, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !48)
 // CHECK:STDOUT: !48 = !{!49, !50}
 // CHECK:STDOUT: !49 = !DILocalVariable(arg: 1, scope: !47, type: !7)
 // CHECK:STDOUT: !50 = !DILocalVariable(arg: 2, scope: !47, type: !7)
diff --git a/toolchain/lower/testdata/interop/cpp/constructor.carbon b/toolchain/lower/testdata/interop/cpp/constructor.carbon
index 1b694de1106a..a9d69a563635 100644
--- a/toolchain/lower/testdata/interop/cpp/constructor.carbon
+++ b/toolchain/lower/testdata/interop/cpp/constructor.carbon
@@ -296,7 +296,7 @@ fn Four() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.C.Cpp"(ptr sret([8 x i8]) %return) #2 !dbg !19 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr sret([8 x i8]) %return) #2 !dbg !19 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN1CC1Ev.carbon_thunk(ptr %return), !dbg !24
 // CHECK:STDOUT:   ret void, !dbg !24
@@ -307,7 +307,7 @@ fn Four() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.93349b0fe912a29b"(ptr sret([8 x i8]) %return) #0 !dbg !25 {
-// CHECK:STDOUT:   call void @"_COp:thunk.C.Cpp"(ptr %return), !dbg !27
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr %return), !dbg !27
 // CHECK:STDOUT:   ret void, !dbg !28
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -353,7 +353,7 @@ fn Four() {
 // CHECK:STDOUT: !16 = !{!17, !17, i64 0}
 // CHECK:STDOUT: !17 = !{!"p1 _ZTS1C", !18, i64 0}
 // CHECK:STDOUT: !18 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !19 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.C.Cpp", scope: null, file: !20, line: 4, type: !21, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !19 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp", scope: null, file: !20, line: 4, type: !21, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !20 = !DIFile(filename: "./default.h", directory: "")
 // CHECK:STDOUT: !21 = !DISubroutineType(types: !22)
 // CHECK:STDOUT: !22 = !{!23}
@@ -407,7 +407,7 @@ fn Four() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.ImplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !22 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.2e5fb550c65543cf.Core:ImplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !22 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN26ImplicitlyDefaultedDefaultC1Ev.carbon_thunk(ptr %return), !dbg !27
 // CHECK:STDOUT:   ret void, !dbg !27
@@ -424,7 +424,7 @@ fn Four() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.ExplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !30 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.cad83ce9b7db87bf.Core:ExplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !30 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN26ExplicitlyDefaultedDefaultC1Ev.carbon_thunk(ptr %return), !dbg !31
 // CHECK:STDOUT:   ret void, !dbg !31
@@ -435,13 +435,13 @@ fn Four() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.22b4681b019423d7"(ptr sret([4 x i8]) %return) #0 !dbg !32 {
-// CHECK:STDOUT:   call void @"_COp:thunk.ImplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !34
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.2e5fb550c65543cf.Core:ImplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !34
 // CHECK:STDOUT:   ret void, !dbg !35
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.1a27c303748a2360"(ptr sret([4 x i8]) %return) #0 !dbg !36 {
-// CHECK:STDOUT:   call void @"_COp:thunk.ExplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !37
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.cad83ce9b7db87bf.Core:ExplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !37
 // CHECK:STDOUT:   ret void, !dbg !38
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -503,7 +503,7 @@ fn Four() {
 // CHECK:STDOUT: !19 = !{!20, !20, i64 0}
 // CHECK:STDOUT: !20 = !{!"p1 _ZTS26ImplicitlyDefaultedDefault", !21, i64 0}
 // CHECK:STDOUT: !21 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.ImplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 2, type: !24, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.2e5fb550c65543cf.Core:ImplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 2, type: !24, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !23 = !DIFile(filename: "./defaulted_default.h", directory: "")
 // CHECK:STDOUT: !24 = !DISubroutineType(types: !25)
 // CHECK:STDOUT: !25 = !{!26}
@@ -511,7 +511,7 @@ fn Four() {
 // CHECK:STDOUT: !27 = !DILocation(line: 2, column: 8, scope: !22)
 // CHECK:STDOUT: !28 = !{!29, !29, i64 0}
 // CHECK:STDOUT: !29 = !{!"p1 _ZTS26ExplicitlyDefaultedDefault", !21, i64 0}
-// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.ExplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 7, type: !24, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.cad83ce9b7db87bf.Core:ExplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 7, type: !24, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !31 = !DILocation(line: 7, column: 3, scope: !30)
 // CHECK:STDOUT: !32 = distinct !DISubprogram(name: "Op", linkageName: "_COp.d288d62be0e5d791:DefaultOrUnformed.Core.22b4681b019423d7", scope: null, file: !33, line: 9, type: !24, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !33 = !DIFile(filename: "min_prelude/parts/default.carbon", directory: "")
@@ -552,7 +552,7 @@ fn Four() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.Copy.Cpp"(ptr sret([4 x i8]) %return, ptr %self) #2 !dbg !22 {
+// CHECK:STDOUT: define void @"_COp:thunk:Copy.692da64e78c7deec.Core:Copy.Cpp"(ptr sret([4 x i8]) %return, ptr %self) #2 !dbg !22 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN4CopyC1ERKS_.carbon_thunk(ptr %self, ptr %return), !dbg !26
 // CHECK:STDOUT:   ret void, !dbg !26
@@ -595,7 +595,7 @@ fn Four() {
 // CHECK:STDOUT: !19 = !{!20, !20, i64 0}
 // CHECK:STDOUT: !20 = !{!"p1 _ZTS4Copy", !21, i64 0}
 // CHECK:STDOUT: !21 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Copy.Cpp", scope: null, file: !23, line: 5, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !24)
+// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Copy.692da64e78c7deec.Core:Copy.Cpp", scope: null, file: !23, line: 5, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !24)
 // CHECK:STDOUT: !23 = !DIFile(filename: "./copy.h", directory: "")
 // CHECK:STDOUT: !24 = !{!25}
 // CHECK:STDOUT: !25 = !DILocalVariable(arg: 1, scope: !22, type: !14)
diff --git a/toolchain/lower/testdata/interop/cpp/parameters.carbon b/toolchain/lower/testdata/interop/cpp/parameters.carbon
index 1db96776a589..ed79da3dddf8 100644
--- a/toolchain/lower/testdata/interop/cpp/parameters.carbon
+++ b/toolchain/lower/testdata/interop/cpp/parameters.carbon
@@ -388,7 +388,7 @@ fn PassValueExpr(y: Cpp.Y) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.X.Cpp"(ptr sret([12 x i8]) %return) #2 !dbg !23 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.17a84649916546b3.Core:X.Cpp"(ptr sret([12 x i8]) %return) #2 !dbg !23 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN1XC1Ev.carbon_thunk(ptr %return), !dbg !28
 // CHECK:STDOUT:   ret void, !dbg !28
@@ -417,7 +417,7 @@ fn PassValueExpr(y: Cpp.Y) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.64f6b96556a8f2d4"(ptr sret([12 x i8]) %return) #0 !dbg !30 {
-// CHECK:STDOUT:   call void @"_COp:thunk.X.Cpp"(ptr %return), !dbg !32
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.17a84649916546b3.Core:X.Cpp"(ptr %return), !dbg !32
 // CHECK:STDOUT:   ret void, !dbg !33
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -464,7 +464,7 @@ fn PassValueExpr(y: Cpp.Y) {
 // CHECK:STDOUT: !20 = !{!21, !21, i64 0}
 // CHECK:STDOUT: !21 = !{!"p1 _ZTS1X", !22, i64 0}
 // CHECK:STDOUT: !22 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.X.Cpp", scope: null, file: !24, line: 2, type: !25, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.17a84649916546b3.Core:X.Cpp", scope: null, file: !24, line: 2, type: !25, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !24 = !DIFile(filename: "./struct.h", directory: "")
 // CHECK:STDOUT: !25 = !DISubroutineType(types: !26)
 // CHECK:STDOUT: !26 = !{!27}
diff --git a/toolchain/lower/testdata/interop/cpp/reference.carbon b/toolchain/lower/testdata/interop/cpp/reference.carbon
index 95c9a6b9eee0..393bb2f6e0ea 100644
--- a/toolchain/lower/testdata/interop/cpp/reference.carbon
+++ b/toolchain/lower/testdata/interop/cpp/reference.carbon
@@ -176,7 +176,7 @@ fn GetRefs() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.C.Cpp"(ptr sret({}) %return) #2 !dbg !29 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr sret({}) %return) #2 !dbg !29 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN1CC1Ev.carbon_thunk(ptr %return), !dbg !33
 // CHECK:STDOUT:   ret void, !dbg !33
@@ -237,7 +237,7 @@ fn GetRefs() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.93349b0fe912a29b"(ptr sret({}) %return) #0 !dbg !43 {
-// CHECK:STDOUT:   call void @"_COp:thunk.C.Cpp"(ptr %return), !dbg !45
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr %return), !dbg !45
 // CHECK:STDOUT:   ret void, !dbg !46
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -297,7 +297,7 @@ fn GetRefs() {
 // CHECK:STDOUT: !26 = !{!27, !27, i64 0}
 // CHECK:STDOUT: !27 = !{!"p1 _ZTS1C", !28, i64 0}
 // CHECK:STDOUT: !28 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.C.Cpp", scope: null, file: !6, line: 5, type: !30, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp", scope: null, file: !6, line: 5, type: !30, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !30 = !DISubroutineType(types: !31)
 // CHECK:STDOUT: !31 = !{!32}
 // CHECK:STDOUT: !32 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
@@ -365,7 +365,7 @@ fn GetRefs() {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define void @"_COp:thunk.C.Cpp"(ptr sret({}) %return) #2 !dbg !29 {
+// CHECK:STDOUT: define void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr sret({}) %return) #2 !dbg !29 {
 // CHECK:STDOUT: entry:
 // CHECK:STDOUT:   call void @_ZN1CC1Ev.carbon_thunk(ptr %return), !dbg !33
 // CHECK:STDOUT:   ret void, !dbg !33
@@ -448,7 +448,7 @@ fn GetRefs() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.d288d62be0e5d791:DefaultOrUnformed.Core.93349b0fe912a29b"(ptr sret({}) %return) #0 !dbg !45 {
-// CHECK:STDOUT:   call void @"_COp:thunk.C.Cpp"(ptr %return), !dbg !47
+// CHECK:STDOUT:   call void @"_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp"(ptr %return), !dbg !47
 // CHECK:STDOUT:   ret void, !dbg !48
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -508,7 +508,7 @@ fn GetRefs() {
 // CHECK:STDOUT: !26 = !{!27, !27, i64 0}
 // CHECK:STDOUT: !27 = !{!"p1 _ZTS1C", !28, i64 0}
 // CHECK:STDOUT: !28 = !{!"any pointer", !9, i64 0}
-// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.C.Cpp", scope: null, file: !6, line: 5, type: !30, spFlags: DISPFlagDefinition, unit: !5)
+// CHECK:STDOUT: !29 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.7b1e6a57c714cdb7.Core:C.Cpp", scope: null, file: !6, line: 5, type: !30, spFlags: DISPFlagDefinition, unit: !5)
 // CHECK:STDOUT: !30 = !DISubroutineType(types: !31)
 // CHECK:STDOUT: !31 = !{!32}
 // CHECK:STDOUT: !32 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
diff --git a/toolchain/lower/testdata/interop/cpp/thunks.carbon b/toolchain/lower/testdata/interop/cpp/thunks.carbon
new file mode 100644
index 000000000000..6c5b25772758
--- /dev/null
+++ b/toolchain/lower/testdata/interop/cpp/thunks.carbon
@@ -0,0 +1,127 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/primitives.carbon
+// EXTRA-ARGS: --clang-arg=-std=c++26
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/interop/cpp/thunks.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/interop/cpp/thunks.carbon
+
+// --- need_thunk.h
+
+struct NeedThunk {
+  NeedThunk();
+  NeedThunk(const NeedThunk&);
+  ~NeedThunk() = default;
+};
+
+// --- multiple_thunks_in_one_class.carbon
+
+library "[[@TEST_NAME]]";
+
+import Cpp library "need_thunk.h";
+
+// We intend to create multiple thunks named `Op` here to demonstrate the need
+// for the mangling to include the signature function.
+fn Call(n: Cpp.NeedThunk) {
+  var unused n2: Cpp.NeedThunk = n;
+}
+
+// CHECK:STDOUT: ; ModuleID = 'multiple_thunks_in_one_class.carbon'
+// CHECK:STDOUT: source_filename = "multiple_thunks_in_one_class.carbon"
+// CHECK:STDOUT: target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+// CHECK:STDOUT: target triple = "x86_64-unknown-linux-gnu"
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CCall.Main(ptr %n) #0 !dbg !11 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %n2.var = alloca [1 x i8], align 1, !dbg !17
+// CHECK:STDOUT:   %.loc9_34.1.temp = alloca [1 x i8], align 1, !dbg !18
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %n2.var), !dbg !17
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %.loc9_34.1.temp), !dbg !18
+// CHECK:STDOUT:   call void @_ZN9NeedThunkC1ERKS_.carbon_thunk(ptr %n, ptr %n2.var), !dbg !18
+// CHECK:STDOUT:   ret void, !dbg !19
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: alwaysinline mustprogress uwtable
+// CHECK:STDOUT: define internal void @_ZN9NeedThunkC1ERKS_.carbon_thunk(ptr noundef %0, ptr noundef %return) #1 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %.addr = alloca ptr, align 8
+// CHECK:STDOUT:   %return.addr = alloca ptr, align 8
+// CHECK:STDOUT:   store ptr %0, ptr %.addr, align 8, !tbaa !20
+// CHECK:STDOUT:   store ptr %return, ptr %return.addr, align 8, !tbaa !20
+// CHECK:STDOUT:   %1 = load ptr, ptr %return.addr, align 8, !tbaa !20
+// CHECK:STDOUT:   %2 = load ptr, ptr %.addr, align 8, !tbaa !20
+// CHECK:STDOUT:   call void @_ZN9NeedThunkC1ERKS_(ptr noundef nonnull align 1 dereferenceable(1) %1, ptr noundef nonnull align 1 dereferenceable(1) %2)
+// CHECK:STDOUT:   ret void
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
+// CHECK:STDOUT: define void @"_COp:thunk:Copy.fdeb6dbda014bd1f.Core:NeedThunk.Cpp"(ptr sret([1 x i8]) %return, ptr %self) #2 !dbg !23 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   call void @_ZN9NeedThunkC1ERKS_.carbon_thunk(ptr %self, ptr %return), !dbg !29
+// CHECK:STDOUT:   ret void, !dbg !29
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
+// CHECK:STDOUT: define void @"_COp:thunk:Destroy.91afe58d20fe9768.Core:NeedThunk.Cpp"(ptr %self) #2 !dbg !30 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   ret void, !dbg !33
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #3
+// CHECK:STDOUT:
+// CHECK:STDOUT: declare void @_ZN9NeedThunkC1ERKS_(ptr noundef nonnull align 1 dereferenceable(1), ptr noundef nonnull align 1 dereferenceable(1)) unnamed_addr #4
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; uselistorder directives
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 1, 0 }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nounwind }
+// CHECK:STDOUT: attributes #1 = { alwaysinline mustprogress uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+// CHECK:STDOUT: attributes #2 = { alwaysinline nounwind }
+// CHECK:STDOUT: attributes #3 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+// CHECK:STDOUT: attributes #4 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1, !2, !3, !4}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!5}
+// CHECK:STDOUT: !llvm.errno.tbaa = !{!7}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = !{i32 8, !"PIC Level", i32 2}
+// CHECK:STDOUT: !3 = !{i32 7, !"PIE Level", i32 2}
+// CHECK:STDOUT: !4 = !{i32 7, !"uwtable", i32 2}
+// CHECK:STDOUT: !5 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !6, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !6 = !DIFile(filename: "multiple_thunks_in_one_class.carbon", directory: "")
+// CHECK:STDOUT: !7 = !{!8, !8, i64 0}
+// CHECK:STDOUT: !8 = !{!"int", !9, i64 0}
+// CHECK:STDOUT: !9 = !{!"omnipotent char", !10, i64 0}
+// CHECK:STDOUT: !10 = !{!"Simple C++ TBAA"}
+// CHECK:STDOUT: !11 = distinct !DISubprogram(name: "Call", linkageName: "_CCall.Main", scope: null, file: !6, line: 8, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !15)
+// CHECK:STDOUT: !12 = !DISubroutineType(types: !13)
+// CHECK:STDOUT: !13 = !{null, !14}
+// CHECK:STDOUT: !14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
+// CHECK:STDOUT: !15 = !{!16}
+// CHECK:STDOUT: !16 = !DILocalVariable(arg: 1, scope: !11, type: !14)
+// CHECK:STDOUT: !17 = !DILocation(line: 9, column: 3, scope: !11)
+// CHECK:STDOUT: !18 = !DILocation(line: 9, column: 34, scope: !11)
+// CHECK:STDOUT: !19 = !DILocation(line: 8, column: 1, scope: !11)
+// CHECK:STDOUT: !20 = !{!21, !21, i64 0}
+// CHECK:STDOUT: !21 = !{!"p1 _ZTS9NeedThunk", !22, i64 0}
+// CHECK:STDOUT: !22 = !{!"any pointer", !9, i64 0}
+// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Copy.fdeb6dbda014bd1f.Core:NeedThunk.Cpp", scope: null, file: !24, line: 4, type: !25, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !27)
+// CHECK:STDOUT: !24 = !DIFile(filename: "./need_thunk.h", directory: "")
+// CHECK:STDOUT: !25 = !DISubroutineType(types: !26)
+// CHECK:STDOUT: !26 = !{!14, !14}
+// CHECK:STDOUT: !27 = !{!28}
+// CHECK:STDOUT: !28 = !DILocalVariable(arg: 1, scope: !23, type: !14)
+// CHECK:STDOUT: !29 = !DILocation(line: 4, column: 3, scope: !23)
+// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Destroy.91afe58d20fe9768.Core:NeedThunk.Cpp", scope: null, file: !24, line: 5, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !31)
+// CHECK:STDOUT: !31 = !{!32}
+// CHECK:STDOUT: !32 = !DILocalVariable(arg: 1, scope: !30, type: !14)
+// CHECK:STDOUT: !33 = !DILocation(line: 5, column: 3, scope: !30)
diff --git a/toolchain/lower/testdata/interop/cpp/void.carbon b/toolchain/lower/testdata/interop/cpp/void.carbon
index 7e4ee2c6eec7..7f76343d278f 100644
--- a/toolchain/lower/testdata/interop/cpp/void.carbon
+++ b/toolchain/lower/testdata/interop/cpp/void.carbon
@@ -182,7 +182,7 @@ fn ConvertFromConstVoidPtr(p: const Cpp.void*) -> const i32* {
 // CHECK:STDOUT: define linkonce_odr ptr @"_CConvert.81a1ecd9155a3498:OptionalAs.f58b2ba767714873.Core.030cb6453373b89b"(ptr %self) #0 !dbg !83 {
 // CHECK:STDOUT:   %temp = alloca ptr, align 8, !dbg !86
 // CHECK:STDOUT:   call void @llvm.lifetime.start.p0(ptr %temp), !dbg !86
-// CHECK:STDOUT:   %1 = call ptr @"_CConvert:thunk.e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4"(ptr %self), !dbg !86
+// CHECK:STDOUT:   %1 = call ptr @"_CConvert:thunk:ImplicitAs.a2a0c15925bee468.Core:e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4"(ptr %self), !dbg !86
 // CHECK:STDOUT:   store ptr %1, ptr %temp, align 8, !dbg !86
 // CHECK:STDOUT:   %2 = load ptr, ptr %temp, align 8, !dbg !86
 // CHECK:STDOUT:   %3 = call ptr @_CSome.Optional.Core.f238af349d589061(ptr %2), !dbg !87
@@ -196,7 +196,7 @@ fn ConvertFromConstVoidPtr(p: const Cpp.void*) -> const i32* {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr ptr @"_CConvert:thunk.e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4"(ptr %self) #3 !dbg !94 {
+// CHECK:STDOUT: define linkonce_odr ptr @"_CConvert:thunk:ImplicitAs.a2a0c15925bee468.Core:e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4"(ptr %self) #3 !dbg !94 {
 // CHECK:STDOUT:   ret ptr %self, !dbg !98
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -336,7 +336,7 @@ fn ConvertFromConstVoidPtr(p: const Cpp.void*) -> const i32* {
 // CHECK:STDOUT: !91 = !DILocalVariable(arg: 1, scope: !89, type: !14)
 // CHECK:STDOUT: !92 = !DILocation(line: 31, column: 12, scope: !89)
 // CHECK:STDOUT: !93 = !DILocation(line: 31, column: 5, scope: !89)
-// CHECK:STDOUT: !94 = distinct !DISubprogram(name: "Convert", linkageName: "_CConvert:thunk.e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4", scope: null, file: !95, line: 40, type: !56, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !96)
+// CHECK:STDOUT: !94 = distinct !DISubprogram(name: "Convert", linkageName: "_CConvert:thunk:ImplicitAs.a2a0c15925bee468.Core:e8f8f92d3d08d149:ImplicitAs.ffd58aeb29886b72.Core.b88d1103f417c6d4", scope: null, file: !95, line: 40, type: !56, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !96)
 // CHECK:STDOUT: !95 = !DIFile(filename: "{{.*}}/prelude/types/cpp/void.carbon", directory: "")
 // CHECK:STDOUT: !96 = !{!97}
 // CHECK:STDOUT: !97 = !DILocalVariable(arg: 1, scope: !94, type: !14)
diff --git a/toolchain/lower/testdata/operators/increment.carbon b/toolchain/lower/testdata/operators/increment.carbon
index 105740d85cc8..8abb35562dc0 100644
--- a/toolchain/lower/testdata/operators/increment.carbon
+++ b/toolchain/lower/testdata/operators/increment.carbon
@@ -44,12 +44,12 @@ fn IncrSigned() {
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define linkonce_odr void @"_COp.Int.9452f4c51951679b.Core:Inc.Core.be1e879c1ad406d8"(ptr %self) #0 !dbg !17 {
-// CHECK:STDOUT:   call void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !21
+// CHECK:STDOUT:   call void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 1), !dbg !21
 // CHECK:STDOUT:   ret void, !dbg !22
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
-// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !23 {
+// CHECK:STDOUT: define linkonce_odr void @"_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda"(ptr %self, i32 %other) #2 !dbg !23 {
 // CHECK:STDOUT:   %1 = call i32 @"_CConvert.1f02987e9673cc00:ImplicitAs.d993a5132e000405.Core.dc9462e6da0d394c"(i32 %other), !dbg !29
 // CHECK:STDOUT:   %2 = load i32, ptr %self, align 4, !dbg !30
 // CHECK:STDOUT:   %3 = add i32 %2, %1, !dbg !30
@@ -98,7 +98,7 @@ fn IncrSigned() {
 // CHECK:STDOUT: !20 = !DILocalVariable(arg: 1, scope: !17, type: !13)
 // CHECK:STDOUT: !21 = !DILocation(line: 365, column: 5, scope: !17)
 // CHECK:STDOUT: !22 = !DILocation(line: 363, column: 3, scope: !17)
-// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk.Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !18, line: 299, type: !24, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
+// CHECK:STDOUT: !23 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:AddAssignWith.808ff30fe61f0791.Core:Int.9452f4c51951679b.Core:AddAssignWith.c820bd8c65a452f9.Core.bb7b2a0b30fd4cda", scope: null, file: !18, line: 299, type: !24, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !26)
 // CHECK:STDOUT: !24 = !DISubroutineType(types: !25)
 // CHECK:STDOUT: !25 = !{null, !13, !13}
 // CHECK:STDOUT: !26 = !{!27, !28}
diff --git a/toolchain/sem_ir/BUILD b/toolchain/sem_ir/BUILD
index bad6f8e23007..22e4e9bd9d66 100644
--- a/toolchain/sem_ir/BUILD
+++ b/toolchain/sem_ir/BUILD
@@ -129,6 +129,7 @@ cc_library(
         "pattern.h",
         "require_impls.h",
         "struct_type_field.h",
+        "thunk.h",
         "type.h",
         "type_info.h",
         "type_iterator.h",
diff --git a/toolchain/sem_ir/file.cpp b/toolchain/sem_ir/file.cpp
index 7d1867dd5b77..aa6b89ab0548 100644
--- a/toolchain/sem_ir/file.cpp
+++ b/toolchain/sem_ir/file.cpp
@@ -38,6 +38,7 @@ File::File(const Parse::Tree* parse_tree, CheckIRId check_ir_id,
       cpp_global_vars_(check_ir_id),
       functions_(check_ir_id),
       cpp_overload_sets_(check_ir_id),
+      thunks_(check_ir_id),
       classes_(check_ir_id),
       interfaces_(check_ir_id),
       named_constraints_(check_ir_id),
@@ -189,6 +190,7 @@ auto File::CollectMemUsage(MemUsage& mem_usage, llvm::StringRef label) const
   mem_usage.Collect(MemUsage::ConcatLabel(label, "cpp_global_vars_"),
                     cpp_global_vars_);
   mem_usage.Collect(MemUsage::ConcatLabel(label, "functions_"), functions_);
+  mem_usage.Collect(MemUsage::ConcatLabel(label, "thunks_"), thunks_);
   mem_usage.Collect(MemUsage::ConcatLabel(label, "classes_"), classes_);
   mem_usage.Collect(MemUsage::ConcatLabel(label, "interfaces_"), interfaces_);
   mem_usage.Collect(MemUsage::ConcatLabel(label, "impls_"), impls_);
diff --git a/toolchain/sem_ir/file.h b/toolchain/sem_ir/file.h
index d70313a483f8..81541b3b0960 100644
--- a/toolchain/sem_ir/file.h
+++ b/toolchain/sem_ir/file.h
@@ -41,6 +41,7 @@
 #include "toolchain/sem_ir/singleton_insts.h"
 #include "toolchain/sem_ir/specific_interface.h"
 #include "toolchain/sem_ir/struct_type_field.h"
+#include "toolchain/sem_ir/thunk.h"
 #include "toolchain/sem_ir/type.h"
 #include "toolchain/sem_ir/type_info.h"
 #include "toolchain/sem_ir/vtable.h"
@@ -174,6 +175,8 @@ class File : public Printable<File> {
   auto cpp_overload_sets() const -> const CppOverloadSetStore& {
     return cpp_overload_sets_;
   }
+  auto thunks() -> ThunkStore& { return thunks_; }
+  auto thunks() const -> const ThunkStore& { return thunks_; }
   auto classes() -> ClassStore& { return classes_; }
   auto classes() const -> const ClassStore& { return classes_; }
   auto interfaces() -> InterfaceStore& { return interfaces_; }
@@ -334,6 +337,9 @@ class File : public Printable<File> {
   // Storage for CppOverloadSet.
   CppOverloadSetStore cpp_overload_sets_;
 
+  // Storage for thunk info records.
+  ThunkStore thunks_;
+
   // Storage for classes.
   ClassStore classes_;
 
diff --git a/toolchain/sem_ir/formatter.cpp b/toolchain/sem_ir/formatter.cpp
index 684ba9966b16..bca624bed22d 100644
--- a/toolchain/sem_ir/formatter.cpp
+++ b/toolchain/sem_ir/formatter.cpp
@@ -569,9 +569,20 @@ auto Formatter::FormatFunction(FunctionId id, const Function& fn) -> void {
                            /*use_hex_escapes=*/true)
           << "\"";
   }
-  if (fn.thunk_decl_id().has_value()) {
+  if (fn.thunk_id().has_value()) {
     out() << " [thunk ";
-    FormatArg(fn.thunk_decl_id());
+    const auto& thunk_info = sem_ir_->thunks().Get(fn.thunk_id());
+    FormatArg(thunk_info.callee_id);
+    if (thunk_info.signature_id.has_value()) {
+      out() << " for ";
+      FormatName(sem_ir_->functions()
+                     .Get(thunk_info.signature_id)
+                     .first_owning_decl_id);
+      if (thunk_info.specific_id.has_value()) {
+        out() << ", ";
+        FormatName(thunk_info.specific_id);
+      }
+    }
     out() << "]";
   }
 
diff --git a/toolchain/sem_ir/function.h b/toolchain/sem_ir/function.h
index 3b10777871f4..535d4b65c608 100644
--- a/toolchain/sem_ir/function.h
+++ b/toolchain/sem_ir/function.h
@@ -212,12 +212,11 @@ struct Function : public EntityWithParamsBase,
                : BuiltinFunctionKind::None;
   }
 
-  // Returns the declaration that this is a non C++ thunk for, or None if this
-  // function is not a thunk.
-  auto thunk_decl_id() const -> InstId {
+  // Returns the ThunkId for this thunk function, or None if it's not a thunk.
+  auto thunk_id() const -> ThunkId {
     return special_function_kind == SpecialFunctionKind::Thunk
-               ? InstId(special_function_kind_data.index)
-               : InstId::None;
+               ? ThunkId(special_function_kind_data.index)
+               : ThunkId::None;
   }
 
   // Returns the declaration of the thunk that should be called to call this
@@ -282,10 +281,10 @@ struct Function : public EntityWithParamsBase,
   }
 
   // Sets that this function is a thunk.
-  auto SetThunk(InstId decl_id) -> void {
+  auto SetThunk(ThunkId thunk_id) -> void {
     CARBON_CHECK(special_function_kind == SpecialFunctionKind::None);
     special_function_kind = SpecialFunctionKind::Thunk;
-    special_function_kind_data = AnyRawId(decl_id.index);
+    special_function_kind_data = AnyRawId(thunk_id.index);
   }
 
   // Sets that this function is a C++ thunk.
diff --git a/toolchain/sem_ir/ids.h b/toolchain/sem_ir/ids.h
index 2010be67498d..81b5307e3d06 100644
--- a/toolchain/sem_ir/ids.h
+++ b/toolchain/sem_ir/ids.h
@@ -307,6 +307,13 @@ struct FunctionId : public IdBase<FunctionId> {
   using IdBase::IdBase;
 };
 
+// The ID of a thunk info record.
+struct ThunkId : public IdBase<ThunkId> {
+  static constexpr llvm::StringLiteral Label = "thunk";
+
+  using IdBase::IdBase;
+};
+
 // The ID of an IR within the set of all IRs being evaluated in the current
 // check execution.
 struct CheckIRId : public IdBase<CheckIRId> {
diff --git a/toolchain/sem_ir/mangler.cpp b/toolchain/sem_ir/mangler.cpp
index 9558757b9e81..6ec33877c4b9 100644
--- a/toolchain/sem_ir/mangler.cpp
+++ b/toolchain/sem_ir/mangler.cpp
@@ -13,6 +13,7 @@
 #include "toolchain/sem_ir/pattern.h"
 #include "toolchain/sem_ir/specific_interface.h"
 #include "toolchain/sem_ir/specific_named_constraint.h"
+#include "toolchain/sem_ir/thunk.h"
 #include "toolchain/sem_ir/typed_insts.h"
 
 namespace Carbon::SemIR {
@@ -25,8 +26,9 @@ auto Mangler::MangleNameId(llvm::raw_ostream& os, SemIR::NameId name_id)
 }
 
 auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
-                                              SemIR::NameScopeId name_scope_id)
-    -> void {
+                                              SemIR::NameScopeId name_scope_id,
+                                              SemIR::SpecificId specific_id,
+                                              char initial_prefix) -> void {
   // Maintain a stack of names for delayed rendering of interface impls.
   struct NameEntry {
     SemIR::NameScopeId name_scope_id;
@@ -40,8 +42,8 @@ auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
   };
   llvm::SmallVector<NameEntry> names_to_render;
   names_to_render.push_back({.name_scope_id = name_scope_id,
-                             .specific_id = SemIR::SpecificId::None,
-                             .prefix = '.'});
+                             .specific_id = specific_id,
+                             .prefix = initial_prefix});
   while (!names_to_render.empty()) {
     auto [name_scope_id, specific_id, prefix] = names_to_render.pop_back_val();
     if (!name_scope_id.has_value()) {
@@ -67,6 +69,7 @@ auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
       continue;
     }
     const auto& name_scope = sem_ir().name_scopes().Get(name_scope_id);
+    auto next_scope_id = name_scope.parent_scope_id();
     CARBON_KIND_SWITCH(sem_ir().insts().Get(name_scope.inst_id())) {
       case CARBON_KIND(SemIR::ImplDecl impl_decl): {
         const auto& impl = sem_ir().impls().Get(impl_decl.impl_id);
@@ -107,7 +110,7 @@ auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
                  .specific_id = class_type.specific_id,
                  .prefix = '.'});
 
-            MangleUnqualifiedClass(os, class_info, class_type.specific_id);
+            MangleUnqualifiedName(os, class_info, class_type.specific_id);
             break;
           }
           case SemIR::AutoType::Kind:
@@ -148,14 +151,24 @@ auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
         continue;
       }
       case CARBON_KIND(SemIR::ClassDecl class_decl): {
-        MangleUnqualifiedClass(os, sem_ir().classes().Get(class_decl.class_id),
-                               specific_id);
+        MangleUnqualifiedName(os, sem_ir().classes().Get(class_decl.class_id),
+                              specific_id);
         break;
       }
       case CARBON_KIND(SemIR::InterfaceDecl interface_decl): {
-        MangleNameId(
-            os, sem_ir().interfaces().Get(interface_decl.interface_id).name_id);
-        MangleSpecificId(os, specific_id);
+        MangleUnqualifiedName(
+            os, sem_ir().interfaces().Get(interface_decl.interface_id),
+            specific_id);
+        break;
+      }
+      case CARBON_KIND(SemIR::InterfaceWithSelfDecl interface_with_self_decl): {
+        MangleUnqualifiedName(
+            os,
+            sem_ir().interfaces().Get(interface_with_self_decl.interface_id),
+            specific_id);
+        // Skip the enclosing `InterfaceDecl` as we already mangled its name.
+        next_scope_id =
+            sem_ir().name_scopes().Get(next_scope_id).parent_scope_id();
         break;
       }
       case SemIR::Namespace::Kind: {
@@ -167,7 +180,7 @@ auto Mangler::MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
         break;
     }
     if (!name_scope.is_imported_package()) {
-      names_to_render.push_back({.name_scope_id = name_scope.parent_scope_id(),
+      names_to_render.push_back({.name_scope_id = next_scope_id,
                                  .specific_id = SemIR::SpecificId::None,
                                  .prefix = '.'});
     }
@@ -190,6 +203,7 @@ auto Mangler::Mangle(SemIR::FunctionId function_id,
   os << "_C";
 
   MangleNameId(os, function.name_id);
+  char separator = '.';
 
   // For a special function, add a marker to disambiguate.
   switch (function.special_function_kind) {
@@ -206,6 +220,20 @@ auto Mangler::Mangle(SemIR::FunctionId function_id,
       break;
     case SemIR::Function::SpecialFunctionKind::Thunk:
       os << ":thunk";
+      if (function.thunk_id().has_value()) {
+        const auto& thunk_info = sem_ir().thunks().Get(function.thunk_id());
+        if (thunk_info.signature_id.has_value()) {
+          const auto& sig_fn =
+              sem_ir().functions().Get(thunk_info.signature_id);
+          // If this ever becomes possible, we'll need to include the signature
+          // name in the mangling too.
+          CARBON_CHECK(sig_fn.name_id == function.name_id,
+                       "Thunk name mismatches signature name");
+          MangleInverseQualifiedNameScope(os, sig_fn.parent_scope_id,
+                                          thunk_info.specific_id, ':');
+          separator = ':';
+        }
+      }
       break;
 
     case SemIR::Function::SpecialFunctionKind::Builtin:
@@ -217,7 +245,8 @@ auto Mangler::Mangle(SemIR::FunctionId function_id,
 
   // TODO: If the function is private, also include the library name as part of
   // the mangling.
-  MangleInverseQualifiedNameScope(os, function.parent_scope_id);
+  MangleInverseQualifiedNameScope(os, function.parent_scope_id,
+                                  SemIR::SpecificId::None, separator);
 
   MangleSpecificId(os, specific_id);
 
@@ -281,10 +310,10 @@ auto Mangler::MangleVTable(const SemIR::Class& class_info,
   return os.TakeStr();
 }
 
-auto Mangler::MangleUnqualifiedClass(llvm::raw_ostream& os,
-                                     const SemIR::Class& class_info,
-                                     SemIR::SpecificId specific_id) -> void {
-  MangleNameId(os, class_info.name_id);
+auto Mangler::MangleUnqualifiedName(llvm::raw_ostream& os,
+                                    const SemIR::EntityWithParamsBase& entity,
+                                    SemIR::SpecificId specific_id) -> void {
+  MangleNameId(os, entity.name_id);
   MangleSpecificId(os, specific_id);
 }
 }  // namespace Carbon::SemIR
diff --git a/toolchain/sem_ir/mangler.h b/toolchain/sem_ir/mangler.h
index 396c02520eb2..dc8398c8289b 100644
--- a/toolchain/sem_ir/mangler.h
+++ b/toolchain/sem_ir/mangler.h
@@ -51,15 +51,16 @@ class Mangler {
   // Mangle this qualified name with inner scope first, working outwards. This
   // may reduce the incidence of common prefixes in the name mangling. (i.e.:
   // every standard library name won't have a common prefix that has to be
-  // skipped and compared before getting to the interesting part)
-  auto MangleInverseQualifiedNameScope(llvm::raw_ostream& os,
-                                       SemIR::NameScopeId name_scope_id)
-      -> void;
+  // skipped and compared before getting to the interesting part).
+  auto MangleInverseQualifiedNameScope(
+      llvm::raw_ostream& os, SemIR::NameScopeId name_scope_id,
+      SemIR::SpecificId specific_id = SemIR::SpecificId::None,
+      char initial_prefix = '.') -> void;
 
-  // Mangle the unqualified name of the specified `Class`.
-  auto MangleUnqualifiedClass(llvm::raw_ostream& os,
-                              const SemIR::Class& class_info,
-                              SemIR::SpecificId specific_id) -> void;
+  // Mangle the unqualified name of the specified entity.
+  auto MangleUnqualifiedName(llvm::raw_ostream& os,
+                             const SemIR::EntityWithParamsBase& entity,
+                             SemIR::SpecificId specific_id) -> void;
 
   // Generates a mangled name using Clang mangling for imported C++ functions.
   auto MangleCppClang(const clang::NamedDecl* decl) -> std::string;
diff --git a/toolchain/sem_ir/thunk.h b/toolchain/sem_ir/thunk.h
new file mode 100644
index 000000000000..a0844f3c547f
--- /dev/null
+++ b/toolchain/sem_ir/thunk.h
@@ -0,0 +1,25 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef CARBON_TOOLCHAIN_SEM_IR_THUNK_H_
+#define CARBON_TOOLCHAIN_SEM_IR_THUNK_H_
+
+#include "toolchain/base/value_store.h"
+#include "toolchain/sem_ir/ids.h"
+
+namespace Carbon::SemIR {
+
+// Metadata tracking information about a thunk's signature, callee, and specific
+// generic parameters.
+struct ThunkInfo {
+  InstId callee_id;
+  FunctionId signature_id = FunctionId::None;
+  SpecificId specific_id = SpecificId::None;
+};
+
+using ThunkStore = ValueStore<ThunkId, ThunkInfo, Tag<CheckIRId>>;
+
+}  // namespace Carbon::SemIR
+
+#endif  // CARBON_TOOLCHAIN_SEM_IR_THUNK_H_