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Fix mangling collision for C++ class template specializations (#7269)

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Carbon-side thunks (for example the `Copy`/`Destroy` witness thunks
generated for imported C++ types) are mangled by Carbon, and their names
incorporate a fingerprint of the involved types. The instruction
fingerprinter identifies a class only by its name and parent scope,
which is sufficient for Carbon classes but not for imported C++ classes:
different specializations of one class template (and other cases such as
types in anonymous namespaces) share a Carbon name and parent scope. As
a result, the thunks for two distinct specializations could mangle to
the same name, producing a single LLVM function with two definitions and
failing `verifyModule` during lowering.

When fingerprinting a class imported from C++, also include the Clang
mangled name of its type.

Test: toolchain/lower/testdata/interop/cpp/thunks.carbon gains a split
with two specializations of one class template, each requiring a thunk;
their thunks now get distinct mangled names instead of colliding.

Assisted-by: Claude Code

---------

Co-authored-by: Christopher Di Bella <cjdb.ns@gmail.com>
This commit is contained in:
Chandler Carruth
2026-05-30 08:13:00 +00:00
committed by GitHub
co-authored by Christopher Di Bella
parent 3ef128ac91
commit 8a59f2a76b
64 changed files with 4762 additions and 4330 deletions
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toolchain/check/testdata/interop/cpp/basics/import/indirect.carbon
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+28 -28
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@@ -218,9 +218,9 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: %tuple.type.87c: type = tuple_type (%i32, %i32) [concrete]
// CHECK:STDOUT: %X: type = class_type @X [concrete]
// CHECK:STDOUT: %X.elem: type = unbound_element_type %X, %i32 [concrete]
// CHECK:STDOUT: %pattern_type.e61: type = pattern_type %X [concrete]
// CHECK:STDOUT: %pattern_type.74a: type = pattern_type %X [concrete]
// CHECK:STDOUT: %int_1.5b8: Core.IntLiteral = int_value 1 [concrete]
// CHECK:STDOUT: %ptr.bfb: type = ptr_type %X [concrete]
// CHECK:STDOUT: %ptr.4ff: type = ptr_type %X [concrete]
// CHECK:STDOUT: %X__carbon_thunk.type: type = fn_type @X__carbon_thunk [concrete]
// CHECK:STDOUT: %X__carbon_thunk: %X__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: %ImplicitAs.type.544: type = facet_type <@ImplicitAs, @ImplicitAs(%i32)> [concrete]
@@ -277,8 +277,8 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: fn @Use() -> out %return.param: %tuple.type.87c {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %ax.patt: %pattern_type.e61 = ref_binding_pattern ax [concrete]
// CHECK:STDOUT: %ax.var_patt: %pattern_type.e61 = var_pattern %ax.patt [concrete]
// CHECK:STDOUT: %ax.patt: %pattern_type.74a = ref_binding_pattern ax [concrete]
// CHECK:STDOUT: %ax.var_patt: %pattern_type.74a = var_pattern %ax.patt [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %ax.var: ref %X = var %ax.var_patt
// CHECK:STDOUT: %int_1: Core.IntLiteral = int_value 1 [concrete = constants.%int_1.5b8]
@@ -290,7 +290,7 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: %Core.IntLiteral.as.ImplicitAs.impl.Convert.call: init %i32 = call %bound_method.loc9_16.2(%int_1) [concrete = constants.%int_1.d5e]
// CHECK:STDOUT: %.loc9_16.1: %i32 = value_of_initializer %Core.IntLiteral.as.ImplicitAs.impl.Convert.call [concrete = constants.%int_1.d5e]
// CHECK:STDOUT: %.loc9_16.2: %i32 = converted %int_1, %.loc9_16.1 [concrete = constants.%int_1.d5e]
// CHECK:STDOUT: %addr: %ptr.bfb = addr_of %.loc9_3.1
// CHECK:STDOUT: %addr: %ptr.4ff = addr_of %.loc9_3.1
// CHECK:STDOUT: %X__carbon_thunk.call: init %empty_tuple.type = call imports.%X__carbon_thunk.decl(%.loc9_16.2, %addr)
// CHECK:STDOUT: %.loc9_3.2: init %X to %.loc9_3.1 = mark_in_place_init %X__carbon_thunk.call
// CHECK:STDOUT: %.loc9_3.3: init %X = converted %int_1, %.loc9_3.2
@@ -331,8 +331,8 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: %i32: type = class_type @Int, @Int(%int_32) [concrete]
// CHECK:STDOUT: %G.type: type = fn_type @G [concrete]
// CHECK:STDOUT: %G: %G.type = struct_value () [concrete]
// CHECK:STDOUT: %Y.13e7b4.1: type = class_type @Y.1 [concrete]
// CHECK:STDOUT: %Y.elem.92b: type = unbound_element_type %Y.13e7b4.1, %i32 [concrete]
// CHECK:STDOUT: %Y.ef9: type = class_type @Y.1 [concrete]
// CHECK:STDOUT: %Y.elem.c50: type = unbound_element_type %Y.ef9, %i32 [concrete]
// CHECK:STDOUT: %Copy.type: type = facet_type <@Copy> [concrete]
// CHECK:STDOUT: %Int.as.Copy.impl.Op.type.b5d: type = fn_type @Int.as.Copy.impl.Op, @Int.as.Copy.impl(%N) [symbolic]
// CHECK:STDOUT: %Int.as.Copy.impl.Op.c85: %Int.as.Copy.impl.Op.type.b5d = struct_value () [symbolic]
@@ -348,21 +348,21 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: %Z: type = class_type @Z [concrete]
// CHECK:STDOUT: %H.type: type = fn_type @H [concrete]
// CHECK:STDOUT: %H: %H.type = struct_value () [concrete]
// CHECK:STDOUT: %Y.13e7b4.2: type = class_type @Y.2 [concrete]
// CHECK:STDOUT: %Y.elem.8ad: type = unbound_element_type %Y.13e7b4.2, %Z [concrete]
// CHECK:STDOUT: %Y.235: type = class_type @Y.2 [concrete]
// CHECK:STDOUT: %Y.elem.f1e: type = unbound_element_type %Y.235, %Z [concrete]
// CHECK:STDOUT: %Z.Z.type: type = fn_type @Z.Z [concrete]
// CHECK:STDOUT: %Z.Z: %Z.Z.type = struct_value () [concrete]
// CHECK:STDOUT: %const.dd4: type = const_type %Z [concrete]
// CHECK:STDOUT: %ptr.5fa: type = ptr_type %const.dd4 [concrete]
// CHECK:STDOUT: %ptr.6ce: type = ptr_type %Z [concrete]
// CHECK:STDOUT: %const.ab6: type = const_type %Z [concrete]
// CHECK:STDOUT: %ptr.bf9: type = ptr_type %const.ab6 [concrete]
// CHECK:STDOUT: %ptr.c6c: type = ptr_type %Z [concrete]
// CHECK:STDOUT: %Z__carbon_thunk.type: type = fn_type @Z__carbon_thunk [concrete]
// CHECK:STDOUT: %Z__carbon_thunk: %Z__carbon_thunk.type = struct_value () [concrete]
// CHECK:STDOUT: %Z.Op.type: type = fn_type @Z.Op [concrete]
// CHECK:STDOUT: %Z.Op: %Z.Op.type = struct_value () [concrete]
// CHECK:STDOUT: %custom_witness.862: <witness> = custom_witness (%Z.Op), @Copy [concrete]
// CHECK:STDOUT: %Copy.facet.429: %Copy.type = facet_value %Z, (%custom_witness.862) [concrete]
// CHECK:STDOUT: %Copy.WithSelf.Op.type.873: type = fn_type @Copy.WithSelf.Op, @Copy.WithSelf(%Copy.facet.429) [concrete]
// CHECK:STDOUT: %.5a8: type = fn_type_with_self_type %Copy.WithSelf.Op.type.873, %Copy.facet.429 [concrete]
// CHECK:STDOUT: %Copy.facet.916: %Copy.type = facet_value %Z, (%custom_witness.862) [concrete]
// CHECK:STDOUT: %Copy.WithSelf.Op.type.8ae: type = fn_type @Copy.WithSelf.Op, @Copy.WithSelf(%Copy.facet.916) [concrete]
// CHECK:STDOUT: %.158: type = fn_type_with_self_type %Copy.WithSelf.Op.type.8ae, %Copy.facet.916 [concrete]
// CHECK:STDOUT: %Y.cpp_destructor.type.300273.2: type = fn_type @Y.cpp_destructor.2 [concrete]
// CHECK:STDOUT: %Y.cpp_destructor.6dd6f2.2: %Y.cpp_destructor.type.300273.2 = struct_value () [concrete]
// CHECK:STDOUT: }
@@ -387,10 +387,10 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: fn @Use() -> out %return.param: %i32 {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %G.ref: %G.type = name_ref G, imports.%Main.G [concrete = constants.%G]
// CHECK:STDOUT: %.loc9_12.1: ref %Y.13e7b4.1 = temporary_storage
// CHECK:STDOUT: %G.call: init %Y.13e7b4.1 to %.loc9_12.1 = call %G.ref()
// CHECK:STDOUT: %.loc9_12.2: ref %Y.13e7b4.1 = temporary %.loc9_12.1, %G.call
// CHECK:STDOUT: %y.ref: %Y.elem.92b = name_ref y, @Y.1.%.1 [concrete = @Y.1.%.1]
// CHECK:STDOUT: %.loc9_12.1: ref %Y.ef9 = temporary_storage
// CHECK:STDOUT: %G.call: init %Y.ef9 to %.loc9_12.1 = call %G.ref()
// CHECK:STDOUT: %.loc9_12.2: ref %Y.ef9 = temporary %.loc9_12.1, %G.call
// CHECK:STDOUT: %y.ref: %Y.elem.c50 = name_ref y, @Y.1.%.1 [concrete = @Y.1.%.1]
// CHECK:STDOUT: %.loc9_13.1: ref %i32 = class_element_access %.loc9_12.2, element0
// CHECK:STDOUT: %.loc9_13.2: %i32 = acquire_value %.loc9_13.1
// CHECK:STDOUT: %impl.elem0: %.a5f = impl_witness_access constants.%Copy.impl_witness.32d, element0 [concrete = constants.%Int.as.Copy.impl.Op.c4a]
@@ -406,23 +406,23 @@ fn UseZ() -> Cpp.A.Z {
// CHECK:STDOUT: fn @UseZ() -> out %return.param: %Z {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %H.ref: %H.type = name_ref H, imports.%Main.H [concrete = constants.%H]
// CHECK:STDOUT: %.loc15_12.1: ref %Y.13e7b4.2 = temporary_storage
// CHECK:STDOUT: %H.call: init %Y.13e7b4.2 to %.loc15_12.1 = call %H.ref()
// CHECK:STDOUT: %.loc15_12.2: ref %Y.13e7b4.2 = temporary %.loc15_12.1, %H.call
// CHECK:STDOUT: %y.ref: %Y.elem.8ad = name_ref y, @Y.2.%.1 [concrete = @Y.2.%.1]
// CHECK:STDOUT: %.loc15_12.1: ref %Y.235 = temporary_storage
// CHECK:STDOUT: %H.call: init %Y.235 to %.loc15_12.1 = call %H.ref()
// CHECK:STDOUT: %.loc15_12.2: ref %Y.235 = temporary %.loc15_12.1, %H.call
// CHECK:STDOUT: %y.ref: %Y.elem.f1e = name_ref y, @Y.2.%.1 [concrete = @Y.2.%.1]
// CHECK:STDOUT: %.loc15_13.1: ref %Z = class_element_access %.loc15_12.2, element0
// CHECK:STDOUT: %.loc15_13.2: %Z = acquire_value %.loc15_13.1
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %impl.elem0: %.5a8 = impl_witness_access constants.%custom_witness.862, element0 [concrete = constants.%Z.Op]
// CHECK:STDOUT: %impl.elem0: %.158 = impl_witness_access constants.%custom_witness.862, element0 [concrete = constants.%Z.Op]
// CHECK:STDOUT: %bound_method: <bound method> = bound_method %.loc15_13.2, %impl.elem0
// CHECK:STDOUT: %.loc15_13.3: ref %Z = temporary_storage
// CHECK:STDOUT: %Op.ref: %Z.Z.type = name_ref Op, imports.%Z.Z.decl [concrete = constants.%Z.Z]
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %.loc15_13.4: ref %Z = value_as_ref %.loc15_13.2
// CHECK:STDOUT: %addr.loc15_13.1: %ptr.6ce = addr_of %.loc15_13.4
// CHECK:STDOUT: %.loc15_13.5: %ptr.5fa = as_compatible %addr.loc15_13.1
// CHECK:STDOUT: %.loc15_13.6: %ptr.5fa = converted %addr.loc15_13.1, %.loc15_13.5
// CHECK:STDOUT: %addr.loc15_13.2: %ptr.6ce = addr_of %.loc13_19.1
// CHECK:STDOUT: %addr.loc15_13.1: %ptr.c6c = addr_of %.loc15_13.4
// CHECK:STDOUT: %.loc15_13.5: %ptr.bf9 = as_compatible %addr.loc15_13.1
// CHECK:STDOUT: %.loc15_13.6: %ptr.bf9 = converted %addr.loc15_13.1, %.loc15_13.5
// CHECK:STDOUT: %addr.loc15_13.2: %ptr.c6c = addr_of %.loc13_19.1
// CHECK:STDOUT: %Z__carbon_thunk.call: init %empty_tuple.type = call imports.%Z__carbon_thunk.decl(%.loc15_13.6, %addr.loc15_13.2)
// CHECK:STDOUT: %.loc15_13.7: init %Z to %.loc13_19.1 = mark_in_place_init %Z__carbon_thunk.call
// CHECK:STDOUT: %Y.cpp_destructor.bound: <bound method> = bound_method %.loc15_12.2, constants.%Y.cpp_destructor.6dd6f2.2