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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/enum/using.carbon
Vendored
+20 -20
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@@ -55,31 +55,31 @@ fn F() {
// CHECK:STDOUT: %F.type: type = fn_type @F [concrete]
// CHECK:STDOUT: %F: %F.type = struct_value () [concrete]
// CHECK:STDOUT: %Color: type = class_type @Color [concrete]
// CHECK:STDOUT: %pattern_type.625: type = pattern_type %Color [concrete]
// CHECK:STDOUT: %int_0.5a5: %Color = int_value 0 [concrete]
// CHECK:STDOUT: %int_1.a87: %Color = int_value 1 [concrete]
// CHECK:STDOUT: %pattern_type.3ad: type = pattern_type %Color [concrete]
// CHECK:STDOUT: %int_0.dc7: %Color = int_value 0 [concrete]
// CHECK:STDOUT: %int_1.c71: %Color = int_value 1 [concrete]
// CHECK:STDOUT: %Zoo: type = class_type @Zoo [concrete]
// CHECK:STDOUT: %Animal: type = class_type @Animal [concrete]
// CHECK:STDOUT: %pattern_type.531: type = pattern_type %Animal [concrete]
// CHECK:STDOUT: %int_0.30a: %Animal = int_value 0 [concrete]
// CHECK:STDOUT: %int_1.292: %Animal = int_value 1 [concrete]
// CHECK:STDOUT: %pattern_type.e29: type = pattern_type %Animal [concrete]
// CHECK:STDOUT: %int_0.f35: %Animal = int_value 0 [concrete]
// CHECK:STDOUT: %int_1.a89: %Animal = int_value 1 [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: %Cpp: <namespace> = namespace file.%Cpp.import_cpp, [concrete] {
// CHECK:STDOUT: .Color = %Color.decl
// CHECK:STDOUT: .Blue = %int_1.a87
// CHECK:STDOUT: .Blue = %int_1.c71
// CHECK:STDOUT: .Zoo = %Zoo.decl
// CHECK:STDOUT: .Dog = %int_1.292
// CHECK:STDOUT: .Dog = %int_1.a89
// CHECK:STDOUT: import Cpp//...
// CHECK:STDOUT: }
// CHECK:STDOUT: %Color.decl: type = class_decl @Color [concrete = constants.%Color] {} {}
// CHECK:STDOUT: %int_0.5a5: %Color = int_value 0 [concrete = constants.%int_0.5a5]
// CHECK:STDOUT: %int_1.a87: %Color = int_value 1 [concrete = constants.%int_1.a87]
// CHECK:STDOUT: %int_0.dc7: %Color = int_value 0 [concrete = constants.%int_0.dc7]
// CHECK:STDOUT: %int_1.c71: %Color = int_value 1 [concrete = constants.%int_1.c71]
// CHECK:STDOUT: %Zoo.decl: type = class_decl @Zoo [concrete = constants.%Zoo] {} {}
// CHECK:STDOUT: %Animal.decl: type = class_decl @Animal [concrete = constants.%Animal] {} {}
// CHECK:STDOUT: %int_0.30a: %Animal = int_value 0 [concrete = constants.%int_0.30a]
// CHECK:STDOUT: %int_1.292: %Animal = int_value 1 [concrete = constants.%int_1.292]
// CHECK:STDOUT: %int_0.f35: %Animal = int_value 0 [concrete = constants.%int_0.f35]
// CHECK:STDOUT: %int_1.a89: %Animal = int_value 1 [concrete = constants.%int_1.a89]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
@@ -89,33 +89,33 @@ fn F() {
// CHECK:STDOUT: fn @F() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %col.patt: %pattern_type.625 = value_binding_pattern col [concrete]
// CHECK:STDOUT: %col.patt: %pattern_type.3ad = value_binding_pattern col [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc18_32: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Color.ref.loc18_35: type = name_ref Color, imports.%Color.decl [concrete = constants.%Color]
// CHECK:STDOUT: %Red.ref: %Color = name_ref Red, imports.%int_0.5a5 [concrete = constants.%int_0.5a5]
// CHECK:STDOUT: %Red.ref: %Color = name_ref Red, imports.%int_0.dc7 [concrete = constants.%int_0.dc7]
// CHECK:STDOUT: %.loc18: type = splice_block %Color.ref.loc18_23 [concrete = constants.%Color] {
// CHECK:STDOUT: %Cpp.ref.loc18_20: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Color.ref.loc18_23: type = name_ref Color, imports.%Color.decl [concrete = constants.%Color]
// CHECK:STDOUT: }
// CHECK:STDOUT: %col: %Color = value_binding col, %Red.ref
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %colb.patt: %pattern_type.625 = value_binding_pattern colb [concrete]
// CHECK:STDOUT: %colb.patt: %pattern_type.3ad = value_binding_pattern colb [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc19_33: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Blue.ref: %Color = name_ref Blue, imports.%int_1.a87 [concrete = constants.%int_1.a87]
// CHECK:STDOUT: %Blue.ref: %Color = name_ref Blue, imports.%int_1.c71 [concrete = constants.%int_1.c71]
// CHECK:STDOUT: %.loc19: type = splice_block %Color.ref.loc19 [concrete = constants.%Color] {
// CHECK:STDOUT: %Cpp.ref.loc19_21: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Color.ref.loc19: type = name_ref Color, imports.%Color.decl [concrete = constants.%Color]
// CHECK:STDOUT: }
// CHECK:STDOUT: %colb: %Color = value_binding colb, %Blue.ref
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %pet.patt: %pattern_type.531 = value_binding_pattern pet [concrete]
// CHECK:STDOUT: %pet.patt: %pattern_type.e29 = value_binding_pattern pet [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc20_37: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Zoo.ref.loc20_40: type = name_ref Zoo, imports.%Zoo.decl [concrete = constants.%Zoo]
// CHECK:STDOUT: %Animal.ref.loc20_44: type = name_ref Animal, imports.%Animal.decl [concrete = constants.%Animal]
// CHECK:STDOUT: %Cat.ref: %Animal = name_ref Cat, imports.%int_0.30a [concrete = constants.%int_0.30a]
// CHECK:STDOUT: %Cat.ref: %Animal = name_ref Cat, imports.%int_0.f35 [concrete = constants.%int_0.f35]
// CHECK:STDOUT: %.loc20: type = splice_block %Animal.ref.loc20_27 [concrete = constants.%Animal] {
// CHECK:STDOUT: %Cpp.ref.loc20_20: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Zoo.ref.loc20_23: type = name_ref Zoo, imports.%Zoo.decl [concrete = constants.%Zoo]
@@ -123,10 +123,10 @@ fn F() {
// CHECK:STDOUT: }
// CHECK:STDOUT: %pet: %Animal = value_binding pet, %Cat.ref
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %pet2.patt: %pattern_type.531 = value_binding_pattern pet2 [concrete]
// CHECK:STDOUT: %pet2.patt: %pattern_type.e29 = value_binding_pattern pet2 [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc21_38: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Dog.ref: %Animal = name_ref Dog, imports.%int_1.292 [concrete = constants.%int_1.292]
// CHECK:STDOUT: %Dog.ref: %Animal = name_ref Dog, imports.%int_1.a89 [concrete = constants.%int_1.a89]
// CHECK:STDOUT: %.loc21: type = splice_block %Animal.ref.loc21 [concrete = constants.%Animal] {
// CHECK:STDOUT: %Cpp.ref.loc21_21: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Zoo.ref.loc21: type = name_ref Zoo, imports.%Zoo.decl [concrete = constants.%Zoo]