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Expose C++ reference returns as Carbon reference returns (#6618)

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Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
This commit is contained in:
Geoff Romer
2026-01-16 18:08:42 +00:00
committed by GitHub
co-authored by Carbon Infra Bot
parent 94d9bff541
commit 95eb7b16bb
5 changed files with 162 additions and 258 deletions
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toolchain/check/cpp/import.cpp
+56 -34
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@@ -1195,9 +1195,26 @@ static auto MakeParamPatternsBlockId(Context& context, SemIR::LocId loc_id,
// are treated as returning a class instance.
// TODO: Support more return types.
static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl) -> TypeExpr {
clang::FunctionDecl* clang_decl)
-> Context::FormExpr {
auto make_init_form = [&](SemIR::TypeInstId type_component_inst_id) {
SemIR::InitForm inst = {
.type_id = SemIR::FormType::TypeId,
.type_component_inst_id = type_component_inst_id,
.index = context.full_pattern_stack().NextCallParamIndex()};
return context.constant_values().GetInstId(TryEvalInst(context, inst));
};
auto make_ref_form = [&](SemIR::TypeInstId type_component_inst_id) {
SemIR::RefForm inst = {.type_id = SemIR::FormType::TypeId,
.type_component_inst_id = type_component_inst_id};
return context.constant_values().GetInstId(TryEvalInst(context, inst));
};
clang::QualType orig_ret_type = clang_decl->getReturnType();
if (!orig_ret_type->isVoidType()) {
bool is_reference = orig_ret_type->isReferenceType();
if (is_reference) {
orig_ret_type = orig_ret_type->getPointeeType();
}
// TODO: We should eventually map reference returns to non-pointer types
// here. We should return by `ref` for `T&` return types once `ref` return
// is implemented.
@@ -1205,24 +1222,33 @@ static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
if (!orig_type_inst_id.has_value()) {
context.TODO(loc_id, llvm::formatv("Unsupported: return type: {0}",
orig_ret_type.getAsString()));
return {.inst_id = SemIR::ErrorInst::TypeInstId,
return {.form_inst_id = SemIR::ErrorInst::InstId,
.type_component_id = SemIR::ErrorInst::TypeInstId,
.type_id = SemIR::ErrorInst::TypeId};
}
Context::FormExpr result = {
.form_inst_id = is_reference ? make_ref_form(orig_type_inst_id)
: make_init_form(orig_type_inst_id),
.type_component_id = orig_type_inst_id,
.type_id = type_id};
return {orig_type_inst_id, type_id};
return result;
}
auto* ctor = dyn_cast<clang::CXXConstructorDecl>(clang_decl);
if (!ctor) {
// void.
return TypeExpr::None;
return {.form_inst_id = SemIR::InstId::None,
.type_component_id = SemIR::TypeInstId::None,
.type_id = SemIR::TypeId::None};
}
// TODO: Make this a `PartialType`.
SemIR::TypeInstId record_type_inst_id = context.types().GetAsTypeInstId(
LookupClangDeclInstId(context, SemIR::ClangDeclKey(ctor->getParent())));
return {
.inst_id = record_type_inst_id,
.form_inst_id = make_init_form(record_type_inst_id),
.type_component_id = record_type_inst_id,
.type_id = context.types().GetTypeIdForTypeInstId(record_type_inst_id)};
}
@@ -1240,16 +1266,17 @@ struct ReturnInfo {
// Constructors are treated as returning a class instance.
static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
clang::FunctionDecl* clang_decl) -> ReturnInfo {
auto [type_inst_id, type_id] = GetReturnTypeExpr(context, loc_id, clang_decl);
if (!type_inst_id.has_value()) {
auto [form_inst_id, type_inst_id, type_id] =
GetReturnTypeExpr(context, loc_id, clang_decl);
if (!form_inst_id.has_value()) {
// void.
return {.return_type_inst_id = type_inst_id,
return {.return_type_inst_id = SemIR::TypeInstId::None,
.return_form_inst_id = SemIR::InstId::None,
.return_patterns_id = SemIR::InstBlockId::None};
}
if (type_inst_id == SemIR::ErrorInst::TypeInstId) {
return {.return_type_inst_id = type_inst_id,
.return_form_inst_id = SemIR::InstId::None,
if (form_inst_id == SemIR::ErrorInst::InstId) {
return {.return_type_inst_id = SemIR::ErrorInst::TypeInstId,
.return_form_inst_id = SemIR::ErrorInst::InstId,
.return_patterns_id = SemIR::InstBlockId::None};
}
auto pattern_type_id = GetPatternType(context, type_id);
@@ -1264,30 +1291,25 @@ static auto GetReturnInfo(Context& context, SemIR::LocId loc_id,
}
SemIR::ImportIRInstId return_type_import_ir_inst_id =
AddImportIRInst(context.sem_ir(), return_type_loc);
SemIR::InstId return_slot_pattern_id = AddPatternInst(
context, MakeImportedLocIdAndInst(
context, return_type_import_ir_inst_id,
SemIR::ReturnSlotPattern({.type_id = pattern_type_id,
.type_inst_id = type_inst_id})));
auto return_index = context.full_pattern_stack().NextCallParamIndex();
SemIR::InstId param_pattern_id = AddPatternInst(
context,
MakeImportedLocIdAndInst(
context, return_type_import_ir_inst_id,
SemIR::OutParamPattern({.type_id = pattern_type_id,
.subpattern_id = return_slot_pattern_id,
.index = return_index})));
auto return_patterns_id = context.inst_blocks().Add({param_pattern_id});
// For consistency with how C++ import handles types, we use TryEvalInst to
// directly create a constant rather than adding it to insts() first.
auto return_form_const_id = TryEvalInst(
context, SemIR::InitForm{.type_id = SemIR::FormType::TypeId,
.type_component_inst_id = type_inst_id,
.index = return_index});
auto return_patterns_id = SemIR::InstBlockId::Empty;
if (auto init_form =
context.insts().TryGetAs<SemIR::InitForm>(form_inst_id)) {
SemIR::InstId return_slot_pattern_id = AddPatternInst(
context, MakeImportedLocIdAndInst(
context, return_type_import_ir_inst_id,
SemIR::ReturnSlotPattern({.type_id = pattern_type_id,
.type_inst_id = type_inst_id})));
auto param_pattern_id = AddPatternInst(
context,
MakeImportedLocIdAndInst(
context, return_type_import_ir_inst_id,
SemIR::OutParamPattern({.type_id = pattern_type_id,
.subpattern_id = return_slot_pattern_id,
.index = init_form->index})));
return_patterns_id = context.inst_blocks().Add({param_pattern_id});
}
return {.return_type_inst_id = type_inst_id,
.return_form_inst_id =
context.constant_values().GetInstId(return_form_const_id),
.return_form_inst_id = form_inst_id,
.return_patterns_id = return_patterns_id};
}