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Make C++ types impl Core.Default. (#6962)

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C++ classes that are default-constructible now implement `Core.Default`
by calling the default constructor.
This commit is contained in:
Richard Smith
2026-03-25 21:07:24 +00:00
committed by GitHub
parent 311670c84a
commit 37b238fa28
49 changed files with 1069 additions and 426 deletions
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toolchain/check/cpp/impl_lookup.cpp
+63 -29
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@@ -119,31 +119,6 @@ static auto BuildCopyWitness(
query_specific_interface_id, {fn_id});
}
static auto BuildDestroyWitness(
Context& context, SemIR::LocId loc_id,
SemIR::ConstantId query_self_const_id,
SemIR::SpecificInterfaceId query_specific_interface_id,
const TypeStructure* best_impl_type_structure,
SemIR::LocId best_impl_loc_id) -> SemIR::InstId {
auto& clang_sema = context.clang_sema();
// TODO: This should provide `Destroy` for enums and other trivially
// destructible types.
auto* class_decl = TypeAsClassDecl(context, query_self_const_id);
if (!class_decl) {
return SemIR::InstId::None;
}
auto decl_info = DeclInfo{.decl = clang_sema.LookupDestructor(class_decl),
.signature = {.num_params = 0}};
auto fn_id = GetFunctionId(context, loc_id, decl_info,
best_impl_type_structure, best_impl_loc_id);
if (fn_id == SemIR::ErrorInst::InstId || fn_id == SemIR::InstId::None) {
return fn_id;
}
return BuildCustomWitness(context, loc_id, query_self_const_id,
query_specific_interface_id, {fn_id});
}
static auto BuildCppUnsafeDerefWitness(
Context& context, SemIR::LocId loc_id,
SemIR::ConstantId query_self_const_id,
@@ -187,6 +162,61 @@ static auto BuildCppUnsafeDerefWitness(
{result_type_id, fn_id});
}
static auto BuildDefaultWitness(
Context& context, SemIR::LocId loc_id,
SemIR::ConstantId query_self_const_id,
SemIR::SpecificInterfaceId query_specific_interface_id,
const TypeStructure* best_impl_type_structure,
SemIR::LocId best_impl_loc_id) -> SemIR::InstId {
auto& clang_sema = context.clang_sema();
auto* class_decl = TypeAsClassDecl(context, query_self_const_id);
if (!class_decl) {
return SemIR::InstId::None;
}
// Clang would produce a warning for classes with uninitialized
// [[clang::requires_init]] fields for which default initialization is
// performed, and we don't have a good place to produce that warning.
// That happens if class_decl->hasUninitializedExplicitInitFields() is true.
//
// TODO: Consider treating such types as not implementing `Default`.
auto decl_info =
DeclInfo{.decl = clang_sema.LookupDefaultConstructor(class_decl),
.signature = {.num_params = 0}};
auto fn_id = GetFunctionId(context, loc_id, decl_info,
best_impl_type_structure, best_impl_loc_id);
if (fn_id == SemIR::ErrorInst::InstId || fn_id == SemIR::InstId::None) {
return fn_id;
}
return BuildCustomWitness(context, loc_id, query_self_const_id,
query_specific_interface_id, {fn_id});
}
static auto BuildDestroyWitness(
Context& context, SemIR::LocId loc_id,
SemIR::ConstantId query_self_const_id,
SemIR::SpecificInterfaceId query_specific_interface_id,
const TypeStructure* best_impl_type_structure,
SemIR::LocId best_impl_loc_id) -> SemIR::InstId {
auto& clang_sema = context.clang_sema();
// TODO: This should provide `Destroy` for enums and other trivially
// destructible types.
auto* class_decl = TypeAsClassDecl(context, query_self_const_id);
if (!class_decl) {
return SemIR::InstId::None;
}
auto decl_info = DeclInfo{.decl = clang_sema.LookupDestructor(class_decl),
.signature = {.num_params = 0}};
auto fn_id = GetFunctionId(context, loc_id, decl_info,
best_impl_type_structure, best_impl_loc_id);
if (fn_id == SemIR::ErrorInst::InstId || fn_id == SemIR::InstId::None) {
return fn_id;
}
return BuildCustomWitness(context, loc_id, query_self_const_id,
query_specific_interface_id, {fn_id});
}
auto LookupCppImpl(Context& context, SemIR::LocId loc_id,
CoreInterface core_interface,
SemIR::ConstantId query_self_const_id,
@@ -198,14 +228,18 @@ auto LookupCppImpl(Context& context, SemIR::LocId loc_id,
return BuildCopyWitness(context, loc_id, query_self_const_id,
query_specific_interface_id,
best_impl_type_structure, best_impl_loc_id);
case CoreInterface::Destroy:
return BuildDestroyWitness(context, loc_id, query_self_const_id,
query_specific_interface_id,
best_impl_type_structure, best_impl_loc_id);
case CoreInterface::CppUnsafeDeref:
return BuildCppUnsafeDerefWitness(
context, loc_id, query_self_const_id, query_specific_interface_id,
best_impl_type_structure, best_impl_loc_id);
case CoreInterface::Default:
return BuildDefaultWitness(context, loc_id, query_self_const_id,
query_specific_interface_id,
best_impl_type_structure, best_impl_loc_id);
case CoreInterface::Destroy:
return BuildDestroyWitness(context, loc_id, query_self_const_id,
query_specific_interface_id,
best_impl_type_structure, best_impl_loc_id);
// IntFitsIn is for Carbon integer types only.
case CoreInterface::IntFitsIn: