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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/convert.carbon
Vendored
+14 -14
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@@ -94,9 +94,9 @@ fn F() {
// CHECK:STDOUT: %i16: type = class_type @Int, @Int(%int_16) [concrete]
// CHECK:STDOUT: %pattern_type.0cb: type = pattern_type %i16 [concrete]
// CHECK:STDOUT: %Enum: type = class_type @Enum [concrete]
// CHECK:STDOUT: %int_0.779: %Enum = int_value 0 [concrete]
// CHECK:STDOUT: %int_0.167: %Enum = int_value 0 [concrete]
// CHECK:STDOUT: %int_0.713: %i16 = int_value 0 [concrete]
// CHECK:STDOUT: %pattern_type.9f7: type = pattern_type %Enum [concrete]
// CHECK:STDOUT: %pattern_type.361: type = pattern_type %Enum [concrete]
// CHECK:STDOUT: %int_42.20e: Core.IntLiteral = int_value 42 [concrete]
// CHECK:STDOUT: %As.type.457: type = facet_type <@As, @As(%i16)> [concrete]
// CHECK:STDOUT: %To: Core.IntLiteral = symbolic_binding To, 0 [symbolic]
@@ -112,10 +112,10 @@ fn F() {
// CHECK:STDOUT: %Core.IntLiteral.as.As.impl.Convert.specific_fn: <specific function> = specific_function %Core.IntLiteral.as.As.impl.Convert.036, @Core.IntLiteral.as.As.impl.Convert(%int_16) [concrete]
// CHECK:STDOUT: %bound_method: <bound method> = bound_method %int_42.20e, %Core.IntLiteral.as.As.impl.Convert.specific_fn [concrete]
// CHECK:STDOUT: %int_42.50d: %i16 = int_value 42 [concrete]
// CHECK:STDOUT: %int_42.7b3: %Enum = int_value 42 [concrete]
// CHECK:STDOUT: %int_42.3d1: %Enum = int_value 42 [concrete]
// CHECK:STDOUT: %Other: type = class_type @Other [concrete]
// CHECK:STDOUT: %pattern_type.da8: type = pattern_type %Other [concrete]
// CHECK:STDOUT: %int_0.9f3: %Other = int_value 0 [concrete]
// CHECK:STDOUT: %pattern_type.7cb: type = pattern_type %Other [concrete]
// CHECK:STDOUT: %int_0.10c: %Other = int_value 0 [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
@@ -126,7 +126,7 @@ fn F() {
// CHECK:STDOUT: import Cpp//...
// CHECK:STDOUT: }
// CHECK:STDOUT: %Enum.decl: type = class_decl @Enum [concrete = constants.%Enum] {} {}
// CHECK:STDOUT: %int_0: %Enum = int_value 0 [concrete = constants.%int_0.779]
// CHECK:STDOUT: %int_0: %Enum = int_value 0 [concrete = constants.%int_0.167]
// CHECK:STDOUT: %Core.import_ref.6c4: @Core.IntLiteral.as.As.impl.%Core.IntLiteral.as.As.impl.Convert.type (%Core.IntLiteral.as.As.impl.Convert.type.fc5) = import_ref Core//prelude/parts/int, loc{{\d+_\d+}}, loaded [symbolic = @Core.IntLiteral.as.As.impl.%Core.IntLiteral.as.As.impl.Convert (constants.%Core.IntLiteral.as.As.impl.Convert.3a8)]
// CHECK:STDOUT: %As.impl_witness_table.2e6 = impl_witness_table (%Core.import_ref.6c4), @Core.IntLiteral.as.As.impl [concrete]
// CHECK:STDOUT: %Other.decl: type = class_decl @Other [concrete = constants.%Other] {} {}
@@ -143,14 +143,14 @@ fn F() {
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc8: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Enum.ref.loc8: type = name_ref Enum, imports.%Enum.decl [concrete = constants.%Enum]
// CHECK:STDOUT: %a.ref.loc8: %Enum = name_ref a, imports.%int_0 [concrete = constants.%int_0.779]
// CHECK:STDOUT: %a.ref.loc8: %Enum = name_ref a, imports.%int_0 [concrete = constants.%int_0.167]
// CHECK:STDOUT: %i16.loc8_37: type = type_literal constants.%i16 [concrete = constants.%i16]
// CHECK:STDOUT: %.loc8_34.1: %i16 = as_compatible %a.ref.loc8 [concrete = constants.%int_0.713]
// CHECK:STDOUT: %.loc8_34.2: %i16 = converted %a.ref.loc8, %.loc8_34.1 [concrete = constants.%int_0.713]
// CHECK:STDOUT: %i16.loc8_17: type = type_literal constants.%i16 [concrete = constants.%i16]
// CHECK:STDOUT: %a: %i16 = value_binding a, %.loc8_34.2
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %b.patt: %pattern_type.9f7 = value_binding_pattern b [concrete]
// CHECK:STDOUT: %b.patt: %pattern_type.361 = value_binding_pattern b [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %int_42: Core.IntLiteral = int_value 42 [concrete = constants.%int_42.20e]
// CHECK:STDOUT: %i16.loc9: type = type_literal constants.%i16 [concrete = constants.%i16]
@@ -163,22 +163,22 @@ fn F() {
// CHECK:STDOUT: %.loc9_32.2: %i16 = converted %int_42, %.loc9_32.1 [concrete = constants.%int_42.50d]
// CHECK:STDOUT: %Cpp.ref.loc9_43: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Enum.ref.loc9_46: type = name_ref Enum, imports.%Enum.decl [concrete = constants.%Enum]
// CHECK:STDOUT: %.loc9_40.1: %Enum = as_compatible %.loc9_32.2 [concrete = constants.%int_42.7b3]
// CHECK:STDOUT: %.loc9_40.2: %Enum = converted %.loc9_32.2, %.loc9_40.1 [concrete = constants.%int_42.7b3]
// CHECK:STDOUT: %.loc9_40.1: %Enum = as_compatible %.loc9_32.2 [concrete = constants.%int_42.3d1]
// CHECK:STDOUT: %.loc9_40.2: %Enum = converted %.loc9_32.2, %.loc9_40.1 [concrete = constants.%int_42.3d1]
// CHECK:STDOUT: %.loc9_20: type = splice_block %Enum.ref.loc9_20 [concrete = constants.%Enum] {
// CHECK:STDOUT: %Cpp.ref.loc9_17: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Enum.ref.loc9_20: type = name_ref Enum, imports.%Enum.decl [concrete = constants.%Enum]
// CHECK:STDOUT: }
// CHECK:STDOUT: %b: %Enum = value_binding b, %.loc9_40.2
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %c.patt: %pattern_type.da8 = value_binding_pattern c [concrete]
// CHECK:STDOUT: %c.patt: %pattern_type.7cb = value_binding_pattern c [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %Cpp.ref.loc10_29: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %a.ref.loc10: %Enum = name_ref a, imports.%int_0 [concrete = constants.%int_0.779]
// CHECK:STDOUT: %a.ref.loc10: %Enum = name_ref a, imports.%int_0 [concrete = constants.%int_0.167]
// CHECK:STDOUT: %Cpp.ref.loc10_38: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Other.ref.loc10_41: type = name_ref Other, imports.%Other.decl [concrete = constants.%Other]
// CHECK:STDOUT: %.loc10_35.1: %Other = as_compatible %a.ref.loc10 [concrete = constants.%int_0.9f3]
// CHECK:STDOUT: %.loc10_35.2: %Other = converted %a.ref.loc10, %.loc10_35.1 [concrete = constants.%int_0.9f3]
// CHECK:STDOUT: %.loc10_35.1: %Other = as_compatible %a.ref.loc10 [concrete = constants.%int_0.10c]
// CHECK:STDOUT: %.loc10_35.2: %Other = converted %a.ref.loc10, %.loc10_35.1 [concrete = constants.%int_0.10c]
// CHECK:STDOUT: %.loc10_20: type = splice_block %Other.ref.loc10_20 [concrete = constants.%Other] {
// CHECK:STDOUT: %Cpp.ref.loc10_17: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
// CHECK:STDOUT: %Other.ref.loc10_20: type = name_ref Other, imports.%Other.decl [concrete = constants.%Other]