Only propagate .Self dependence in facet types from extended constraints (#7253)

When forming the constant value of a `where` expression, don't consider it to be `.Self`-dependent if the dependence only comes from the RHS of the `where`. More generally, ignore `.Self` dependence when evaluating a facet type unless it comes from an extended interface or named constraint. While we can get other kinds of constraint from the left-hand side of a `where`, such constraints must either come from the right-hand side of other `where` expressions or be extend constraints. This fixes a crash in lowering caused by a concrete function containing a `.Self`-symbolic `where` constant. Assisted-by: Gemini via Antigravity
2026-09-24 15:10:12 +01:00 · 2026-05-27 22:04:48 +00:00
parent 7569aff619
commit 9986d0da69
9 changed files with 254 additions and 87 deletions
@@ -475,33 +475,6 @@ static auto RequireConstantValue(EvalContext& eval_context,
  return SemIR::ErrorInst::InstId;
 }

-// If the given instruction is constant, returns its constant value. Otherwise,
-// produces an error diagnostic. When determining the phase of the result,
-// ignore any dependence on `.Self`.
-//
-// This is used when evaluating facet types, for which `where` expressions using
-// `.Self` should not be considered symbolic
-// - `Interface where .Self impls I and .A = bool` -> concrete
-// - `T:! type` ... `Interface where .A = T` -> symbolic, since uses `T` which
-//   is symbolic and not due to `.Self`.
-static auto RequireConstantValueIgnoringPeriodSelf(EvalContext& eval_context,
-                                                   SemIR::InstId inst_id,
-                                                   Phase* phase)
-    -> SemIR::InstId {
-  if (!inst_id.has_value()) {
-    return SemIR::InstId::None;
-  }
-  Phase constant_phase = *phase;
-  auto const_inst_id =
-      RequireConstantValue(eval_context, inst_id, &constant_phase);
-  // Since LatestPhase(x, Phase::Concrete) == x, this is equivalent to replacing
-  // Phase::PeriodSelfSymbolic with Phase::Concrete.
-  if (constant_phase != Phase::PeriodSelfSymbolic) {
-    *phase = LatestPhase(*phase, constant_phase);
-  }
-  return const_inst_id;
-}
-
 // Gets a constant value for an `inst_id`, diagnosing when the input is not
 // constant, and CHECKing that it is concrete. Should only be used in contexts
 // where non-concrete constants cannot appear.
@@ -723,6 +696,10 @@ static auto GetConstantFacetTypeInfo(EvalContext& eval_context,
                                     Phase* phase) -> SemIR::FacetTypeInfo {
  SemIR::FacetTypeInfo info = {};

+  // Phase of constraints whose `.Self` refers to the type constrained by this
+  // facet type.
+  Phase self_phase = Phase::Concrete;
+
  info.extend_constraints.reserve(orig.extend_constraints.size());
  for (const auto& extend : orig.extend_constraints) {
    // TODO: Add GetConstantValue for SpecificInterface.
@@ -737,8 +714,8 @@ static auto GetConstantFacetTypeInfo(EvalContext& eval_context,
    // TODO: Add GetConstantValue for SpecificInterface.
    info.self_impls_constraints.push_back(
        {.interface_id = self_impls.interface_id,
-         .specific_id =
-             GetConstantValue(eval_context, self_impls.specific_id, phase)});
+         .specific_id = GetConstantValue(eval_context, self_impls.specific_id,
+                                         &self_phase)});
  }

  info.extend_named_constraints.reserve(orig.extend_named_constraints.size());
@@ -756,21 +733,21 @@ static auto GetConstantFacetTypeInfo(EvalContext& eval_context,
    // TODO: Add GetConstantValue for SpecificNamedConstraint.
    info.self_impls_named_constraints.push_back(
        {.named_constraint_id = self_impls.named_constraint_id,
-         .specific_id =
-             GetConstantValue(eval_context, self_impls.specific_id, phase)});
+         .specific_id = GetConstantValue(eval_context, self_impls.specific_id,
+                                         &self_phase)});
  }

  info.type_impls_interfaces.reserve(orig.type_impls_interfaces.size());
  for (const auto& type_impls : orig.type_impls_interfaces) {
    info.type_impls_interfaces.push_back(
        {.self_type =
-             GetConstantValue(eval_context, type_impls.self_type, phase),
+             GetConstantValue(eval_context, type_impls.self_type, &self_phase),
         // TODO: Add GetConstantValue for SpecificInterface.
         .specific_interface = {
             .interface_id = type_impls.specific_interface.interface_id,
             .specific_id = GetConstantValue(
                 eval_context, type_impls.specific_interface.specific_id,
-                 phase)}});
+                 &self_phase)}});
  }

  info.type_impls_named_constraints.reserve(
@@ -778,14 +755,14 @@ static auto GetConstantFacetTypeInfo(EvalContext& eval_context,
  for (const auto& type_impls : orig.type_impls_named_constraints) {
    info.type_impls_named_constraints.push_back(
        {.self_type =
-             GetConstantValue(eval_context, type_impls.self_type, phase),
+             GetConstantValue(eval_context, type_impls.self_type, &self_phase),
         // TODO: Add GetConstantValue for SpecificNamedConstraint.
         .specific_named_constraint = {
             .named_constraint_id =
                 type_impls.specific_named_constraint.named_constraint_id,
             .specific_id = GetConstantValue(
                 eval_context, type_impls.specific_named_constraint.specific_id,
-                 phase)}});
+                 &self_phase)}});
  }

  // Rewrite constraints are resolved first before replacing them with their
@@ -806,14 +783,19 @@ static auto GetConstantFacetTypeInfo(EvalContext& eval_context,
  }

  for (auto& rewrite : info.rewrite_constraints) {
-    // `where` requirements using `.Self` should not be considered symbolic.
-    auto lhs_id = RequireConstantValueIgnoringPeriodSelf(eval_context,
-                                                         rewrite.lhs_id, phase);
-    auto rhs_id = RequireConstantValueIgnoringPeriodSelf(eval_context,
-                                                         rewrite.rhs_id, phase);
+    auto lhs_id =
+        RequireConstantValue(eval_context, rewrite.lhs_id, &self_phase);
+    auto rhs_id =
+        RequireConstantValue(eval_context, rewrite.rhs_id, &self_phase);
    rewrite = {.lhs_id = lhs_id, .rhs_id = rhs_id};
  }

+  // Update phase, ignoring `.Self` dependence from constraints whose `.Self` is
+  // scoped to this facet type.
+  if (self_phase > Phase::PeriodSelfSymbolic) {
+    *phase = LatestPhase(*phase, self_phase);
+  }
+
  // TODO: Process other requirements.
  info.other_requirements = orig.other_requirements;

@@ -274,8 +274,8 @@ fn F(unused U:! type, V:! Core.Destroy where {} impls Core.ImplicitAs(.Self)) {
 // CHECK:STDOUT:   %ImplicitAs.WithSelf.Convert.751: %ImplicitAs.WithSelf.Convert.type.7c0 = struct_value () [symbolic]
 // CHECK:STDOUT:   %.Self.as_type: type = facet_access_type %.Self.d91 [symbolic_self]
 // CHECK:STDOUT:   %ImplicitAs.type.33a: type = facet_type <@ImplicitAs, @ImplicitAs(%.Self.as_type)> [symbolic_self]
-// CHECK:STDOUT:   %Destroy_where.type: type = facet_type <@Destroy where %empty_struct_type impls @ImplicitAs, @ImplicitAs(%.Self.as_type)> [symbolic_self]
-// CHECK:STDOUT:   %pattern_type.785: type = pattern_type %Destroy_where.type [symbolic_self]
+// CHECK:STDOUT:   %Destroy_where.type: type = facet_type <@Destroy where %empty_struct_type impls @ImplicitAs, @ImplicitAs(%.Self.as_type)> [concrete]
+// CHECK:STDOUT:   %pattern_type.785: type = pattern_type %Destroy_where.type [concrete]
 // CHECK:STDOUT:   %V: %Destroy_where.type = symbolic_binding V, 1 [symbolic]
 // CHECK:STDOUT:   %F.type: type = fn_type @F [concrete]
 // CHECK:STDOUT:   %F: %F.type = struct_value () [concrete]
@@ -347,7 +347,7 @@ fn F(unused U:! type, V:! Core.Destroy where {} impls Core.ImplicitAs(.Self)) {
 // CHECK:STDOUT:       %.loc9_17.2: type = type_literal type [concrete = type]
 // CHECK:STDOUT:     }
 // CHECK:STDOUT:     %U.loc9_14.2: type = symbolic_binding U, 0 [symbolic = %U.loc9_14.1 (constants.%U)]
-// CHECK:STDOUT:     %.loc9_40.1: type = splice_block %.loc9_40.2 [symbolic_self = constants.%Destroy_where.type] {
+// CHECK:STDOUT:     %.loc9_40.1: type = splice_block %.loc9_40.2 [concrete = constants.%Destroy_where.type] {
 // CHECK:STDOUT:       %.Self.loc9_24: %type = symbolic_binding .Self [symbolic_self = constants.%.Self.c39]
 // CHECK:STDOUT:       %Core.ref.loc9_27: <namespace> = name_ref Core, imports.%Core [concrete = imports.%Core]
 // CHECK:STDOUT:       %Destroy.ref: type = name_ref Destroy, imports.%Core.Destroy [concrete = constants.%Destroy.type]
@@ -360,7 +360,7 @@ fn F(unused U:! type, V:! Core.Destroy where {} impls Core.ImplicitAs(.Self)) {
 // CHECK:STDOUT:       %.loc9_76: type = converted %.Self.ref, %.Self.as_type [symbolic_self = constants.%.Self.as_type]
 // CHECK:STDOUT:       %ImplicitAs.type.loc9: type = facet_type <@ImplicitAs, @ImplicitAs(constants.%.Self.as_type)> [symbolic_self = constants.%ImplicitAs.type.33a]
 // CHECK:STDOUT:       %.loc9_47.2: type = converted %.loc9_47.1, constants.%empty_struct_type [concrete = constants.%empty_struct_type]
-// CHECK:STDOUT:       %.loc9_40.2: type = where_expr [symbolic_self = constants.%Destroy_where.type] {
+// CHECK:STDOUT:       %.loc9_40.2: type = where_expr [concrete = constants.%Destroy_where.type] {
 // CHECK:STDOUT:         requirement_base_facet_type %Destroy.ref
 // CHECK:STDOUT:         requirement_impls %.loc9_47.2, %ImplicitAs.type.loc9
 // CHECK:STDOUT:       }
@@ -62,9 +62,9 @@ fn G(T:! L) {
  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_non_final_impl.carbon:[[@LINE+7]]:3: error: cannot convert type `T` that implements `L` into type implementing `type where C(.Self) impls M and C(.Self).(M.M0) = {}` [ConversionFailureFacetToFacet]
  // CHECK:STDERR:   F(T);
  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_non_final_impl.carbon:[[@LINE-10]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_non_final_impl.carbon:[[@LINE-10]]:13: note: initializing generic parameter `U` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(unused U:! type where C(.Self) impls (M where .M0 = {})) {}
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F(T);
 }
@@ -107,9 +107,9 @@ fn G(T:! L) {
  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_type_differs.carbon:[[@LINE+7]]:3: error: cannot convert type `T` that implements `L` into type implementing `type where C(.Self) impls M and C(.Self).(M.M0) = {}` [ConversionFailureFacetToFacet]
  // CHECK:STDERR:   F(T);
  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_type_differs.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_type_type_differs.carbon:[[@LINE-6]]:13: note: initializing generic parameter `U` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(unused U:! type where C(.Self) impls (M where .M0 = {})) {}
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F(T);
 }
@@ -137,9 +137,9 @@ fn G(T:! L) {
  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_non_final_impl.carbon:[[@LINE+7]]:3: error: cannot convert type `T` that implements `L` into type implementing `type where C impls M(.Self) and C.(M(.Self).M0) = {}` [ConversionFailureFacetToFacet]
  // CHECK:STDERR:   F(T);
  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_non_final_impl.carbon:[[@LINE-10]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_non_final_impl.carbon:[[@LINE-10]]:13: note: initializing generic parameter `U` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(unused U:! type where C impls (M(.Self) where .M0 = {})) {}
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F(T);
 }
@@ -182,9 +182,9 @@ fn G(T:! L) {
  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_type_differs.carbon:[[@LINE+7]]:3: error: cannot convert type `T` that implements `L` into type implementing `type where C impls M(.Self) and C.(M(.Self).M0) = {}` [ConversionFailureFacetToFacet]
  // CHECK:STDERR:   F(T);
  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_type_differs.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_where_impls_tests_associated_constant_of_generic_interface_type_differs.carbon:[[@LINE-6]]:13: note: initializing generic parameter `U` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(unused U:! type where C impls (M(.Self) where .M0 = {})) {}
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F(T);
 }
@@ -356,9 +356,9 @@ fn G() {
  // CHECK:STDERR: fail_concrete_witness_without_impl.carbon:[[@LINE+7]]:3: error: cannot convert type `C` into type implementing `I where .(I.I1) impls J` [ConversionFailureTypeToFacet]
  // CHECK:STDERR:   F(C);
  // CHECK:STDERR:   ^~~~
-  // CHECK:STDERR: fail_concrete_witness_without_impl.carbon:[[@LINE-16]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_concrete_witness_without_impl.carbon:[[@LINE-16]]:6: note: initializing generic parameter `_` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(_:! I where .I1 impls J) {}
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:      ^~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F(C);
 }
@@ -93,9 +93,9 @@ fn CallF() {
  // CHECK:STDERR: fail_todo_constrained_fn.carbon:[[@LINE+7]]:3: error: cannot convert type `{}` into type implementing `I where {} impls Core.ImplicitAs(.Self) and .(I.V) = {}` [ConversionFailureTypeToFacet]
  // CHECK:STDERR:   F({});
  // CHECK:STDERR:   ^~~~~
-  // CHECK:STDERR: fail_todo_constrained_fn.carbon:[[@LINE-7]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
+  // CHECK:STDERR: fail_todo_constrained_fn.carbon:[[@LINE-7]]:6: note: initializing generic parameter `T` declared here [InitializingGenericParam]
  // CHECK:STDERR: fn F(T:! I where {} impls Core.ImplicitAs(.Self) and .V = {});
-  // CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  // CHECK:STDERR:      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  // CHECK:STDERR:
  F({});
 }
@@ -750,8 +750,8 @@ fn CallF() {
 // CHECK:STDOUT:   %ImplicitAs.type.7ec: type = facet_type <@ImplicitAs, @ImplicitAs(%.Self.as_type)> [symbolic_self]
 // CHECK:STDOUT:   %I.lookup_impl_witness.5fc: <witness> = lookup_impl_witness %.Self.908, @I [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %.Self.as_type = impl_witness_access %I.lookup_impl_witness.5fc, element0 [symbolic_self]
-// CHECK:STDOUT:   %I_where.type: type = facet_type <@I where %empty_struct_type impls @ImplicitAs, @ImplicitAs(%.Self.as_type) and %impl.elem0 = %empty_struct> [symbolic_self]
-// CHECK:STDOUT:   %pattern_type.010: type = pattern_type %I_where.type [symbolic_self]
+// CHECK:STDOUT:   %I_where.type: type = facet_type <@I where %empty_struct_type impls @ImplicitAs, @ImplicitAs(%.Self.as_type) and %impl.elem0 = %empty_struct> [concrete]
+// CHECK:STDOUT:   %pattern_type.010: type = pattern_type %I_where.type [concrete]
 // CHECK:STDOUT:   %T: %I_where.type = symbolic_binding T, 0 [symbolic]
 // CHECK:STDOUT:   %F.type: type = fn_type @F [concrete]
 // CHECK:STDOUT:   %F: %F.type = struct_value () [concrete]
@@ -780,7 +780,7 @@ fn CallF() {
 // CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [concrete = constants.%F] {
 // CHECK:STDOUT:     %T.patt: %pattern_type.010 = symbolic_binding_pattern T, 0 [concrete]
 // CHECK:STDOUT:   } {
-// CHECK:STDOUT:     %.loc8_12.1: type = splice_block %.loc8_12.2 [symbolic_self = constants.%I_where.type] {
+// CHECK:STDOUT:     %.loc8_12.1: type = splice_block %.loc8_12.2 [concrete = constants.%I_where.type] {
 // CHECK:STDOUT:       %.Self.loc8_7: %type = symbolic_binding .Self [symbolic_self = constants.%.Self.c39]
 // CHECK:STDOUT:       %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
 // CHECK:STDOUT:       %.Self.loc8_12: %I.type = symbolic_binding .Self [symbolic_self = constants.%.Self.908]
@@ -800,7 +800,7 @@ fn CallF() {
 // CHECK:STDOUT:       %.loc8_60.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:       %empty_struct: %empty_struct_type = struct_value () [concrete = constants.%empty_struct]
 // CHECK:STDOUT:       %.loc8_60.2: %empty_struct_type = converted %.loc8_60.1, %empty_struct [concrete = constants.%empty_struct]
-// CHECK:STDOUT:       %.loc8_12.2: type = where_expr [symbolic_self = constants.%I_where.type] {
+// CHECK:STDOUT:       %.loc8_12.2: type = where_expr [concrete = constants.%I_where.type] {
 // CHECK:STDOUT:         requirement_base_facet_type %I.ref
 // CHECK:STDOUT:         requirement_impls %.loc8_19.2, %ImplicitAs.type
 // CHECK:STDOUT:         requirement_rewrite %impl.elem0, %.loc8_60.2
@@ -477,7 +477,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %impl.elem0.354: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element0 [symbolic_self]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %impl.elem1.fdc: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element1 [symbolic_self]
-// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [symbolic_self]
+// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [concrete]
 // CHECK:STDOUT:   %R: %CppRangeForIterate_where.type = symbolic_binding R, 0 [symbolic]
 // CHECK:STDOUT:   %R.as_type: type = facet_access_type %R [symbolic]
 // CHECK:STDOUT:   %pattern_type.ff859f.2: type = pattern_type %R.as_type [symbolic]
@@ -524,7 +524,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Iterator.Op.type.f11: type = fn_type @Iterator.Op.1 [concrete]
 // CHECK:STDOUT:   %Iterator.Op.78e: %Iterator.Op.type.f11 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.b91: <witness> = custom_witness (%Iterator.Op.78e), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.665: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.7e3fb2.1, %custom_witness.b91) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.665: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.7e3fb2.1, %custom_witness.b91) [concrete]
 // CHECK:STDOUT:   %Iterator.a7566c.2: type = class_type @Iterator.2 [concrete]
 // CHECK:STDOUT:   %ConstRange.Begin.type: type = fn_type @ConstRange.Begin [concrete]
 // CHECK:STDOUT:   %ConstRange.Begin: %ConstRange.Begin.type = struct_value () [concrete]
@@ -535,7 +535,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Iterator.Op.type.798: type = fn_type @Iterator.Op.2 [concrete]
 // CHECK:STDOUT:   %Iterator.Op.250: %Iterator.Op.type.798 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.018: <witness> = custom_witness (%Iterator.Op.250), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.57a: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.7e3fb2.2, %custom_witness.018) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.57a: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.7e3fb2.2, %custom_witness.018) [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.Begin.type.a13: type = fn_type @CppRangeForIterate.WithSelf.Begin, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.d24) [concrete]
 // CHECK:STDOUT:   %.a34: type = fn_type_with_self_type %CppRangeForIterate.WithSelf.Begin.type.a13, %CppRangeForIterate.facet.d24 [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.End.type.e9f: type = fn_type @CppRangeForIterate.WithSelf.End, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.d24) [concrete]
@@ -714,7 +714,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %impl.elem0.354: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element0 [symbolic_self]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %impl.elem1.fdc: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element1 [symbolic_self]
-// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [symbolic_self]
+// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [concrete]
 // CHECK:STDOUT:   %R: %CppRangeForIterate_where.type = symbolic_binding R, 0 [symbolic]
 // CHECK:STDOUT:   %R.as_type: type = facet_access_type %R [symbolic]
 // CHECK:STDOUT:   %pattern_type.ff859f.2: type = pattern_type %R.as_type [symbolic]
@@ -765,7 +765,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Sentinel.Op.type.f11: type = fn_type @Sentinel.Op.1 [concrete]
 // CHECK:STDOUT:   %Sentinel.Op.78e: %Sentinel.Op.type.f11 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.b916b4.2: <witness> = custom_witness (%Sentinel.Op.78e), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.8f5: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.607036.1, %custom_witness.b916b4.1, %custom_witness.b916b4.2) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.8f5: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.607036.1, %custom_witness.b916b4.1, %custom_witness.b916b4.2) [concrete]
 // CHECK:STDOUT:   %Iterator.a7566c.2: type = class_type @Iterator.2 [concrete]
 // CHECK:STDOUT:   %Sentinel.885798.2: type = class_type @Sentinel.2 [concrete]
 // CHECK:STDOUT:   %ConstRange.Begin.type: type = fn_type @ConstRange.Begin [concrete]
@@ -780,7 +780,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Sentinel.Op.type.798: type = fn_type @Sentinel.Op.2 [concrete]
 // CHECK:STDOUT:   %Sentinel.Op.250: %Sentinel.Op.type.798 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.0183d1.2: <witness> = custom_witness (%Sentinel.Op.250), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.058: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.607036.2, %custom_witness.0183d1.1, %custom_witness.0183d1.2) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.058: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.607036.2, %custom_witness.0183d1.1, %custom_witness.0183d1.2) [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.Begin.type.dc4: type = fn_type @CppRangeForIterate.WithSelf.Begin, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.5b8) [concrete]
 // CHECK:STDOUT:   %.314: type = fn_type_with_self_type %CppRangeForIterate.WithSelf.Begin.type.dc4, %CppRangeForIterate.facet.5b8 [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.End.type.143: type = fn_type @CppRangeForIterate.WithSelf.End, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.5b8) [concrete]
@@ -965,7 +965,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %impl.elem0.354: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element0 [symbolic_self]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %impl.elem1.fdc: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element1 [symbolic_self]
-// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [symbolic_self]
+// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [concrete]
 // CHECK:STDOUT:   %R: %CppRangeForIterate_where.type = symbolic_binding R, 0 [symbolic]
 // CHECK:STDOUT:   %R.as_type: type = facet_access_type %R [symbolic]
 // CHECK:STDOUT:   %pattern_type.ff859f.2: type = pattern_type %R.as_type [symbolic]
@@ -1012,7 +1012,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Iterator.Op.type.37d: type = fn_type @Iterator.Op.1 [concrete]
 // CHECK:STDOUT:   %Iterator.Op.26b: %Iterator.Op.type.37d = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.415: <witness> = custom_witness (%Iterator.Op.26b), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.c35: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.827774.1, %custom_witness.415) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.c35: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.827774.1, %custom_witness.415) [concrete]
 // CHECK:STDOUT:   %Iterator.b6bc8f.2: type = class_type @Iterator.2 [concrete]
 // CHECK:STDOUT:   %Begin.type.793876.2: type = fn_type @Begin.2 [concrete]
 // CHECK:STDOUT:   %Begin.1544bb.2: %Begin.type.793876.2 = struct_value () [concrete]
@@ -1023,7 +1023,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Iterator.Op.type.152: type = fn_type @Iterator.Op.2 [concrete]
 // CHECK:STDOUT:   %Iterator.Op.84b: %Iterator.Op.type.152 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.0d3: <witness> = custom_witness (%Iterator.Op.84b), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.057: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.827774.2, %custom_witness.0d3) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.057: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.827774.2, %custom_witness.0d3) [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.Begin.type.bfa: type = fn_type @CppRangeForIterate.WithSelf.Begin, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.a7f) [concrete]
 // CHECK:STDOUT:   %.73f: type = fn_type_with_self_type %CppRangeForIterate.WithSelf.Begin.type.bfa, %CppRangeForIterate.facet.a7f [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.End.type.c37: type = fn_type @CppRangeForIterate.WithSelf.End, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.a7f) [concrete]
@@ -1202,7 +1202,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %impl.elem0.354: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element0 [symbolic_self]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %impl.elem1.fdc: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element1 [symbolic_self]
-// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [symbolic_self]
+// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [concrete]
 // CHECK:STDOUT:   %R: %CppRangeForIterate_where.type = symbolic_binding R, 0 [symbolic]
 // CHECK:STDOUT:   %R.as_type: type = facet_access_type %R [symbolic]
 // CHECK:STDOUT:   %pattern_type.ff859f.2: type = pattern_type %R.as_type [symbolic]
@@ -1253,7 +1253,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Sentinel.Op.type.37d: type = fn_type @Sentinel.Op.1 [concrete]
 // CHECK:STDOUT:   %Sentinel.Op.26b: %Sentinel.Op.type.37d = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.415faa.2: <witness> = custom_witness (%Sentinel.Op.26b), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.b34: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.1bf5e5.1, %custom_witness.415faa.1, %custom_witness.415faa.2) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.b34: %CppRangeForIterate_where.type = facet_value %MutableRange, (%custom_witness.1bf5e5.1, %custom_witness.415faa.1, %custom_witness.415faa.2) [concrete]
 // CHECK:STDOUT:   %Iterator.b6bc8f.2: type = class_type @Iterator.2 [concrete]
 // CHECK:STDOUT:   %Sentinel.50a788.2: type = class_type @Sentinel.2 [concrete]
 // CHECK:STDOUT:   %Begin.type.793876.2: type = fn_type @Begin.2 [concrete]
@@ -1268,7 +1268,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Sentinel.Op.type.152: type = fn_type @Sentinel.Op.2 [concrete]
 // CHECK:STDOUT:   %Sentinel.Op.84b: %Sentinel.Op.type.152 = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.0d3cfa.2: <witness> = custom_witness (%Sentinel.Op.84b), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value.11c: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.1bf5e5.2, %custom_witness.0d3cfa.1, %custom_witness.0d3cfa.2) [symbolic_self]
+// CHECK:STDOUT:   %facet_value.11c: %CppRangeForIterate_where.type = facet_value %ConstRange, (%custom_witness.1bf5e5.2, %custom_witness.0d3cfa.1, %custom_witness.0d3cfa.2) [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.Begin.type.bf8: type = fn_type @CppRangeForIterate.WithSelf.Begin, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.d1e) [concrete]
 // CHECK:STDOUT:   %.504: type = fn_type_with_self_type %CppRangeForIterate.WithSelf.Begin.type.bf8, %CppRangeForIterate.facet.d1e [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.End.type.580: type = fn_type @CppRangeForIterate.WithSelf.End, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.d1e) [concrete]
@@ -1453,7 +1453,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %impl.elem0.354: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element0 [symbolic_self]
 // CHECK:STDOUT:   %Destroy.type: type = facet_type <@Destroy> [concrete]
 // CHECK:STDOUT:   %impl.elem1.fdc: type = impl_witness_access %CppRangeForIterate.lookup_impl_witness.ae8, element1 [symbolic_self]
-// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [symbolic_self]
+// CHECK:STDOUT:   %CppRangeForIterate_where.type: type = facet_type <@CppRangeForIterate where %impl.elem0.354 impls @Destroy and %impl.elem1.fdc impls @Destroy> [concrete]
 // CHECK:STDOUT:   %R: %CppRangeForIterate_where.type = symbolic_binding R, 0 [symbolic]
 // CHECK:STDOUT:   %R.as_type: type = facet_access_type %R [symbolic]
 // CHECK:STDOUT:   %pattern_type.ff859f.2: type = pattern_type %R.as_type [symbolic]
@@ -1498,7 +1498,7 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   %Iterator.Op.type: type = fn_type @Iterator.Op [concrete]
 // CHECK:STDOUT:   %Iterator.Op: %Iterator.Op.type = struct_value () [concrete]
 // CHECK:STDOUT:   %custom_witness.2d3: <witness> = custom_witness (%Iterator.Op), @Destroy [concrete]
-// CHECK:STDOUT:   %facet_value: %CppRangeForIterate_where.type = facet_value %MutableAndConstRange, (%custom_witness.827, %custom_witness.2d3) [symbolic_self]
+// CHECK:STDOUT:   %facet_value: %CppRangeForIterate_where.type = facet_value %MutableAndConstRange, (%custom_witness.827, %custom_witness.2d3) [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.Begin.type.706: type = fn_type @CppRangeForIterate.WithSelf.Begin, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.98b) [concrete]
 // CHECK:STDOUT:   %.ff3: type = fn_type_with_self_type %CppRangeForIterate.WithSelf.Begin.type.706, %CppRangeForIterate.facet.98b [concrete]
 // CHECK:STDOUT:   %CppRangeForIterate.WithSelf.End.type.5f8: type = fn_type @CppRangeForIterate.WithSelf.End, @CppRangeForIterate.WithSelf(%CppRangeForIterate.facet.98b) [concrete]
@@ -1425,7 +1425,7 @@ constraint N {
 // CHECK:STDOUT:   %.Self.c14: %Z.type = symbolic_binding .Self [symbolic_self]
 // CHECK:STDOUT:   %.Self.as_type.324: type = facet_access_type %.Self.c14 [symbolic_self]
 // CHECK:STDOUT:   %Y.type.e27: type = facet_type <@Y, @Y(%.Self.as_type.324)> [symbolic_self]
-// CHECK:STDOUT:   %Z_where.type.87e: type = facet_type <@Z where .Self impls @Y, @Y(%.Self.as_type.324)> [symbolic_self]
+// CHECK:STDOUT:   %Z_where.type.87e: type = facet_type <@Z where .Self impls @Y, @Y(%.Self.as_type.324)> [concrete]
 // CHECK:STDOUT:   %Z_where.type.f50: type = facet_type <@Z where .Self impls @Y, @Y(%Self.as_type.4b4)> [symbolic]
 // CHECK:STDOUT:   %.Self.as_type.246: type = facet_access_type %.Self.c39 [symbolic_self]
 // CHECK:STDOUT:   %facet_type: type = facet_type <@Z & @Y, @Y(%.Self.as_type.246)> [symbolic_self]
@@ -1457,7 +1457,7 @@ constraint N {
 // CHECK:STDOUT:     %Y.type: type = facet_type <@Y, @Y(constants.%.Self.as_type.324)> [symbolic_self = constants.%Y.type.e27]
 // CHECK:STDOUT:     %.Self.as_type.loc10_25: type = facet_access_type %.Self.ref.loc10_25 [symbolic_self = constants.%.Self.as_type.324]
 // CHECK:STDOUT:     %.loc10_25: type = converted %.Self.ref.loc10_25, %.Self.as_type.loc10_25 [symbolic_self = constants.%.Self.as_type.324]
-// CHECK:STDOUT:     %.loc10_19: type = where_expr [symbolic_self = constants.%Z_where.type.87e] {
+// CHECK:STDOUT:     %.loc10_19: type = where_expr [concrete = constants.%Z_where.type.87e] {
 // CHECK:STDOUT:       requirement_base_facet_type %Z.ref
 // CHECK:STDOUT:       requirement_impls %.loc10_25, %Y.type
 // CHECK:STDOUT:     }
@@ -1518,7 +1518,7 @@ constraint N {
 // CHECK:STDOUT:   %.Self.as_type: type = facet_access_type %.Self.069 [symbolic_self]
 // CHECK:STDOUT:   %C.e61: type = class_type @C, @C(%.Self.as_type) [symbolic_self]
 // CHECK:STDOUT:   %Y.type.313: type = facet_type <@Y, @Y(%.Self.as_type)> [symbolic_self]
-// CHECK:STDOUT:   %Z_where.type.d5dfdf.1: type = facet_type <@Z where %C.e61 impls @Y, @Y(%.Self.as_type)> [symbolic_self]
+// CHECK:STDOUT:   %Z_where.type.d5dfdf.1: type = facet_type <@Z where %C.e61 impls @Y, @Y(%.Self.as_type)> [concrete]
 // CHECK:STDOUT:   %C.e28: type = class_type @C, @C(%Self.as_type) [symbolic]
 // CHECK:STDOUT:   %Z_where.type.d5dfdf.2: type = facet_type <@Z where %C.e28 impls @Y, @Y(%Self.as_type)> [symbolic]
 // CHECK:STDOUT:   %T.067: %Z.type = symbolic_binding T, 0 [symbolic]
@@ -1552,7 +1552,7 @@ constraint N {
 // CHECK:STDOUT:     %.Self.as_type.loc10_47: type = facet_access_type %.Self.ref.loc10_42 [symbolic_self = constants.%.Self.as_type]
 // CHECK:STDOUT:     %.loc10_47: type = converted %.Self.ref.loc10_42, %.Self.as_type.loc10_47 [symbolic_self = constants.%.Self.as_type]
 // CHECK:STDOUT:     %Y.type: type = facet_type <@Y, @Y(constants.%.Self.as_type)> [symbolic_self = constants.%Y.type.313]
-// CHECK:STDOUT:     %.loc10_19: type = where_expr [symbolic_self = constants.%Z_where.type.d5dfdf.1] {
+// CHECK:STDOUT:     %.loc10_19: type = where_expr [concrete = constants.%Z_where.type.d5dfdf.1] {
 // CHECK:STDOUT:       requirement_base_facet_type %Z.ref
 // CHECK:STDOUT:       requirement_impls %C.loc10_32, %Y.type
 // CHECK:STDOUT:     }
@@ -439,8 +439,8 @@ fn F() {
 // CHECK:STDOUT:   %K.lookup_impl_witness: <witness> = lookup_impl_witness %.Self.cb7, @K [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %L.type = impl_witness_access %K.lookup_impl_witness, element0 [symbolic_self]
 // CHECK:STDOUT:   %as_type: type = facet_access_type %impl.elem0 [symbolic_self]
-// CHECK:STDOUT:   %K_where.type: type = facet_type <@K where %impl.elem0 impls @M> [symbolic_self]
-// CHECK:STDOUT:   %pattern_type: type = pattern_type %K_where.type [symbolic_self]
+// CHECK:STDOUT:   %K_where.type: type = facet_type <@K where %impl.elem0 impls @M> [concrete]
+// CHECK:STDOUT:   %pattern_type: type = pattern_type %K_where.type [concrete]
 // CHECK:STDOUT:   %W: %K_where.type = symbolic_binding W, 0 [symbolic]
 // CHECK:STDOUT:   %AssociatedTypeImpls.type: type = fn_type @AssociatedTypeImpls [concrete]
 // CHECK:STDOUT:   %AssociatedTypeImpls: %AssociatedTypeImpls.type = struct_value () [concrete]
@@ -450,7 +450,7 @@ fn F() {
 // CHECK:STDOUT:   %AssociatedTypeImpls.decl: %AssociatedTypeImpls.type = fn_decl @AssociatedTypeImpls [concrete = constants.%AssociatedTypeImpls] {
 // CHECK:STDOUT:     %W.patt: %pattern_type = symbolic_binding_pattern W, 0 [concrete]
 // CHECK:STDOUT:   } {
-// CHECK:STDOUT:     %.loc12_30.1: type = splice_block %.loc12_30.2 [symbolic_self = constants.%K_where.type] {
+// CHECK:STDOUT:     %.loc12_30.1: type = splice_block %.loc12_30.2 [concrete = constants.%K_where.type] {
 // CHECK:STDOUT:       %.Self.loc12_25: %type = symbolic_binding .Self [symbolic_self = constants.%.Self.c39]
 // CHECK:STDOUT:       %K.ref: type = name_ref K, file.%K.decl [concrete = constants.%K.type]
 // CHECK:STDOUT:       %.Self.loc12_30: %K.type = symbolic_binding .Self [symbolic_self = constants.%.Self.cb7]
@@ -462,7 +462,7 @@ fn F() {
 // CHECK:STDOUT:       %M.ref: type = name_ref M, file.%M.decl [concrete = constants.%M.type]
 // CHECK:STDOUT:       %as_type: type = facet_access_type %impl.elem0 [symbolic_self = constants.%as_type]
 // CHECK:STDOUT:       %.loc12_36.2: type = converted %impl.elem0, %as_type [symbolic_self = constants.%as_type]
-// CHECK:STDOUT:       %.loc12_30.2: type = where_expr [symbolic_self = constants.%K_where.type] {
+// CHECK:STDOUT:       %.loc12_30.2: type = where_expr [concrete = constants.%K_where.type] {
 // CHECK:STDOUT:         requirement_base_facet_type %K.ref
 // CHECK:STDOUT:         requirement_impls %.loc12_36.2, %M.ref
 // CHECK:STDOUT:       }
@@ -0,0 +1,105 @@
+// 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/int.carbon
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/impl/period_self.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/impl/period_self.carbon
+
+// --- library_with_period_self_in_impl.carbon
+
+library "[[@TEST_NAME]]";
+
+interface J {}
+
+class A(T:! type) {}
+class B {}
+
+impl forall [T:! type] A(T) as J {}
+
+impl forall [T:! type where A(.Self) impls J] A(T) as Core.As(T*) {
+  fn Convert[self: A(T)]() -> T* {
+    return self as T*;
+  }
+}
+
+fn F[T:! type](x: A(T)) {
+  x as T*;
+}
+
+// --- import_period_self_in_impl.carbon
+
+library "[[@TEST_NAME]]";
+
+import library "library_with_period_self_in_impl";
+
+fn G(a: A(B)) {
+  F(a);
+}
+
+// CHECK:STDOUT: ; ModuleID = 'library_with_period_self_in_impl.carbon'
+// CHECK:STDOUT: source_filename = "library_with_period_self_in_impl.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "library_with_period_self_in_impl.carbon", directory: "")
+// CHECK:STDOUT: ; ModuleID = 'import_period_self_in_impl.carbon'
+// CHECK:STDOUT: source_filename = "import_period_self_in_impl.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CG.Main(ptr %a) #0 !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   call void @_CF.Main.b4fc7929164fb220(ptr %a), !dbg !10
+// CHECK:STDOUT:   ret void, !dbg !11
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define linkonce_odr void @_CF.Main.b4fc7929164fb220(ptr %x) #0 !dbg !12 {
+// CHECK:STDOUT:   %1 = call ptr @"_CConvert.A.5d7343568c0b5715.Main:As.00d5ad878904f3d1.Core.d9476ddaeffa1656"(ptr %x), !dbg !16
+// CHECK:STDOUT:   ret void, !dbg !17
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define linkonce_odr ptr @"_CConvert.A.5d7343568c0b5715.Main:As.00d5ad878904f3d1.Core.d9476ddaeffa1656"(ptr %self) #0 !dbg !18 {
+// CHECK:STDOUT:   %1 = call ptr @"_CConvert.A.5d7343568c0b5715.Main:As.00d5ad878904f3d1.Core.d9476ddaeffa1656"(ptr %self), !dbg !23
+// CHECK:STDOUT:   ret ptr %1, !dbg !24
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nounwind }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "import_period_self_in_impl.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !3, line: 6, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !8)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{null, !7}
+// CHECK:STDOUT: !7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
+// CHECK:STDOUT: !8 = !{!9}
+// CHECK:STDOUT: !9 = !DILocalVariable(arg: 1, scope: !4, type: !7)
+// CHECK:STDOUT: !10 = !DILocation(line: 7, column: 3, scope: !4)
+// CHECK:STDOUT: !11 = !DILocation(line: 6, column: 1, scope: !4)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.b4fc7929164fb220", scope: null, file: !13, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !14)
+// CHECK:STDOUT: !13 = !DIFile(filename: "library_with_period_self_in_impl.carbon", directory: "")
+// CHECK:STDOUT: !14 = !{!15}
+// CHECK:STDOUT: !15 = !DILocalVariable(arg: 1, scope: !12, type: !7)
+// CHECK:STDOUT: !16 = !DILocation(line: 18, column: 3, scope: !12)
+// CHECK:STDOUT: !17 = !DILocation(line: 17, column: 1, scope: !12)
+// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "Convert", linkageName: "_CConvert.A.5d7343568c0b5715.Main:As.00d5ad878904f3d1.Core.d9476ddaeffa1656", scope: null, file: !13, line: 12, type: !19, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !21)
+// CHECK:STDOUT: !19 = !DISubroutineType(types: !20)
+// CHECK:STDOUT: !20 = !{!7, !7}
+// CHECK:STDOUT: !21 = !{!22}
+// CHECK:STDOUT: !22 = !DILocalVariable(arg: 1, scope: !18, type: !7)
+// CHECK:STDOUT: !23 = !DILocation(line: 13, column: 12, scope: !18)
+// CHECK:STDOUT: !24 = !DILocation(line: 13, column: 5, scope: !18)
@@ -10,6 +10,10 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/interface/where.carbon

+// --- basic.carbon
+
+library "[[@TEST_NAME]]";
+
 interface I {
  let T:! type;
  fn F();
@@ -22,8 +26,37 @@ impl C as I where .T = () {
  }
 }

-// CHECK:STDOUT: ; ModuleID = 'where.carbon'
-// CHECK:STDOUT: source_filename = "where.carbon"
+// --- no_period_self_dependence.carbon
+
+library "[[@TEST_NAME]]";
+
+class C {}
+class D {}
+class E {}
+
+interface I(T:! type) { fn F[self: Self](); }
+interface J(T:! type) {}
+
+impl D as J(E) {}
+
+// The type of `T` is not `.Self`-dependent, because `.Self` appears after
+// `where`.
+impl forall [T:! type where D impls J(.Self)] C as I(T) {
+  fn F[unused self: Self]() {}
+}
+
+fn F(a: C) {
+  a.(I(E).F)();
+}
+
+fn G() {
+  // This is a concrete, non-`.Self`-dependent type.
+  // (Lowering would assert if it sees a dependent constant.)
+  let unused t: type = type where D impls J(.Self);
+}
+
+// CHECK:STDOUT: ; ModuleID = 'basic.carbon'
+// CHECK:STDOUT: source_filename = "basic.carbon"
 // CHECK:STDOUT:
 // CHECK:STDOUT: ; Function Attrs: nounwind
 // CHECK:STDOUT: define void @"_CF.C.Main:I.Main"() #0 !dbg !4 {
@@ -39,8 +72,55 @@ impl C as I where .T = () {
 // CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
-// CHECK:STDOUT: !3 = !DIFile(filename: "where.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.C.Main:I.Main", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !3 = !DIFile(filename: "basic.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.C.Main:I.Main", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{null}
-// CHECK:STDOUT: !7 = !DILocation(line: 21, column: 3, scope: !4)
+// CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
+// CHECK:STDOUT: ; ModuleID = 'no_period_self_dependence.carbon'
+// CHECK:STDOUT: source_filename = "no_period_self_dependence.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CF.Main(ptr %a) #0 !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   call void @"_CF.C.Main:I.5d7343568c0b5715.Main.36f6a86118c8cac1"(ptr %a), !dbg !10
+// CHECK:STDOUT:   ret void, !dbg !11
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define void @_CG.Main() #0 !dbg !12 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   ret void, !dbg !15
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nounwind
+// CHECK:STDOUT: define linkonce_odr void @"_CF.C.Main:I.5d7343568c0b5715.Main.36f6a86118c8cac1"(ptr %self) #0 !dbg !16 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   ret void, !dbg !19
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nounwind }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "no_period_self_dependence.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !8)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{null, !7}
+// CHECK:STDOUT: !7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
+// CHECK:STDOUT: !8 = !{!9}
+// CHECK:STDOUT: !9 = !DILocalVariable(arg: 1, scope: !4, type: !7)
+// CHECK:STDOUT: !10 = !DILocation(line: 20, column: 3, scope: !4)
+// CHECK:STDOUT: !11 = !DILocation(line: 19, column: 1, scope: !4)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !3, line: 23, type: !13, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
+// CHECK:STDOUT: !14 = !{null}
+// CHECK:STDOUT: !15 = !DILocation(line: 23, column: 1, scope: !12)
+// CHECK:STDOUT: !16 = distinct !DISubprogram(name: "F", linkageName: "_CF.C.Main:I.5d7343568c0b5715.Main.36f6a86118c8cac1", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !17)
+// CHECK:STDOUT: !17 = !{!18}
+// CHECK:STDOUT: !18 = !DILocalVariable(arg: 1, scope: !16, type: !7)
+// CHECK:STDOUT: !19 = !DILocation(line: 16, column: 3, scope: !16)