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changes LookupCppImpl's return to handle multiple associated entities (#6916)

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`LookupCppImpl` handles exactly one function ID, so core interfaces with
multiple associated entities were regarded as unsupported. This commit
adds support for a single associated function with a single associated
constant.

Note: associated constants are still TODO.

---------

Co-authored-by: Dana Jansens <danakj@orodu.net>
This commit is contained in:
Christopher Di Bella
2026-03-19 22:03:39 +00:00
committed by GitHub
co-authored by Dana Jansens
parent 08148f3a3a
commit fd2d210c63
2 changed files with 41 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/check/cpp/impl_lookup.cpp
+39 -19
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@@ -57,14 +57,13 @@ struct DeclInfo {
};
} // namespace
// Given a DeclInfo of the C++ function to call that will act as an impl for a
// specific interface, construct a custom witness for that function.
static auto BuildWitnessForDeclInfo(
Context& context, SemIR::LocId loc_id, DeclInfo decl_info,
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 {
// Finds the InstId for the C++ function that is called by a specific interface.
// Returns SemIR::InstId::None if a C++ function is not found, and
// SemIR::ErrorInst::InstId if an error occurs.
static auto GetFunctionId(Context& context, SemIR::LocId loc_id,
DeclInfo decl_info,
const TypeStructure* best_impl_type_structure,
SemIR::LocId best_impl_loc_id) -> SemIR::InstId {
if (!decl_info.decl) {
// The C++ type is not able to implement the interface.
return SemIR::InstId::None;
@@ -91,8 +90,7 @@ static auto BuildWitnessForDeclInfo(
static_cast<void>(best_impl_type_structure);
static_cast<void>(best_impl_loc_id);
return BuildCustomWitness(context, loc_id, query_self_const_id,
query_specific_interface_id, {fn_id});
return fn_id;
}
static auto BuildCopyWitness(
@@ -112,9 +110,13 @@ static auto BuildCopyWitness(
auto decl_info = DeclInfo{.decl = clang_sema.LookupCopyingConstructor(
class_decl, clang::Qualifiers::Const),
.signature = {.num_params = 1}};
return BuildWitnessForDeclInfo(
context, loc_id, decl_info, query_self_const_id,
query_specific_interface_id, best_impl_type_structure, best_impl_loc_id);
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(
@@ -133,9 +135,13 @@ static auto BuildDestroyWitness(
}
auto decl_info = DeclInfo{.decl = clang_sema.LookupDestructor(class_decl),
.signature = {.num_params = 0}};
return BuildWitnessForDeclInfo(
context, loc_id, decl_info, query_self_const_id,
query_specific_interface_id, best_impl_type_structure, best_impl_loc_id);
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(
@@ -162,9 +168,23 @@ static auto BuildCppUnsafeDerefWitness(
}
auto decl_info =
DeclInfo{.decl = *candidates.begin(), .signature = {.num_params = 0}};
return BuildWitnessForDeclInfo(
context, loc_id, decl_info, query_self_const_id,
query_specific_interface_id, best_impl_type_structure, best_impl_loc_id);
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;
}
auto result_type_id =
context.functions()
.Get(context.insts().GetAs<SemIR::FunctionDecl>(fn_id).function_id)
.return_type_inst_id;
if (result_type_id == SemIR::ErrorInst::InstId) {
return SemIR::ErrorInst::InstId;
}
return BuildCustomWitness(context, loc_id, query_self_const_id,
query_specific_interface_id,
{result_type_id, fn_id});
}
auto LookupCppImpl(Context& context, SemIR::LocId loc_id,