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Interop: map C++ std::string_view into Carbon str when importing. (#5985)

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We assume these types have the same representation. For now, that will
only be the case for libc++ on 64-bit targets, because libc++ puts the
size field first, and `Core.String` always uses a 64-bit size field even
on 32-bit targets.

---------

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
This commit is contained in:
Richard Smith
2025-08-27 01:02:39 +00:00
committed by GitHub
co-authored by Chandler Carruth
parent 82ba1a43a1
commit bd90fe1d9b
8 changed files with 356 additions and 26 deletions
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toolchain/check/import_cpp.cpp
+36 -9
View File
@@ -29,6 +29,7 @@
#include "toolchain/check/class.h"
#include "toolchain/check/context.h"
#include "toolchain/check/convert.h"
#include "toolchain/check/cpp_custom_type_mapping.h"
#include "toolchain/check/cpp_thunk.h"
#include "toolchain/check/diagnostic_helpers.h"
#include "toolchain/check/eval.h"
@@ -1200,7 +1201,24 @@ static auto MapBuiltinType(Context& context, SemIR::LocId loc_id,
// TODO: Handle floating-point types that map to named aliases.
}
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
return TypeExpr::None;
}
// Determines whether record_decl is a C++ class that has a custom mapping into
// Carbon, and if so, returns the corresponding Carbon type. Otherwise returns
// None.
static auto LookupCustomRecordType(Context& context,
const clang::CXXRecordDecl* record_decl)
-> TypeExpr {
switch (GetCustomCppTypeMapping(record_decl)) {
case CustomCppTypeMapping::None:
return TypeExpr::None;
case CustomCppTypeMapping::Str:
return MakeStringType(
context,
AddImportIRInst(context.sem_ir(), record_decl->getLocation()));
}
}
// Maps a C++ tag type (class, struct, union, enum) to a Carbon type.
@@ -1210,12 +1228,21 @@ static auto MapTagType(Context& context, const clang::TagType& type)
CARBON_CHECK(tag_decl);
// Check if the declaration is already mapped.
SemIR::InstId record_inst_id = LookupClangDeclInstId(context, tag_decl);
if (!record_inst_id.has_value()) {
record_inst_id = ImportTagDecl(context, tag_decl);
SemIR::InstId tag_inst_id = LookupClangDeclInstId(context, tag_decl);
if (!tag_inst_id.has_value()) {
if (auto* record_decl = dyn_cast<clang::CXXRecordDecl>(tag_decl)) {
auto custom_type = LookupCustomRecordType(context, record_decl);
if (custom_type.inst_id.has_value()) {
context.sem_ir().clang_decls().Add(
{.decl = record_decl, .inst_id = custom_type.inst_id});
return custom_type;
}
}
tag_inst_id = ImportTagDecl(context, tag_decl);
}
SemIR::TypeInstId record_type_inst_id =
context.types().GetAsTypeInstId(record_inst_id);
context.types().GetAsTypeInstId(tag_inst_id);
return {
.inst_id = record_type_inst_id,
.type_id = context.types().GetTypeIdForTypeInstId(record_type_inst_id)};
@@ -1237,7 +1264,7 @@ static auto MapNonWrapperType(Context& context, SemIR::LocId loc_id,
CARBON_CHECK(!type.hasQualifiers() && !type->isPointerType(),
"Should not see wrapper types here");
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
return TypeExpr::None;
}
// Maps a qualified C++ type to a Carbon type.
@@ -1254,7 +1281,7 @@ static auto MapQualifiedType(Context& context, clang::QualType type,
// TODO: Support other qualifiers.
if (!quals.empty()) {
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
return TypeExpr::None;
}
return type_expr;
@@ -1269,7 +1296,7 @@ static auto MapPointerType(Context& context, clang::QualType type,
!nullability.has_value() ||
*nullability != clang::NullabilityKind::NonNull) {
// TODO: Support nullable pointers.
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
return TypeExpr::None;
}
SemIR::TypeId pointer_type_id =
@@ -1467,7 +1494,7 @@ static auto GetReturnTypeExpr(Context& context, SemIR::LocId loc_id,
if (!isa<clang::CXXConstructorDecl>(clang_decl)) {
// void.
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
return TypeExpr::None;
}
// TODO: Make this a `PartialType`.