From 38ae676da848dd38111190843d5bd521e9ba3eed Mon Sep 17 00:00:00 2001 From: David Blaikie Date: Thu, 19 Mar 2026 21:42:47 +0000 Subject: [PATCH] Reverse Interop: Nested namespace support --- toolchain/check/cpp/generate_ast.cpp | 45 ++++++++++++------- .../interop/cpp/reverse/simple.carbon | 17 +------ 2 files changed, 30 insertions(+), 32 deletions(-) diff --git a/toolchain/check/cpp/generate_ast.cpp b/toolchain/check/cpp/generate_ast.cpp index 8e064057765b..ee1d9a6a4410 100644 --- a/toolchain/check/cpp/generate_ast.cpp +++ b/toolchain/check/cpp/generate_ast.cpp @@ -20,6 +20,7 @@ #include "clang/Sema/MultiplexExternalSemaSource.h" #include "clang/Sema/Sema.h" #include "common/check.h" +#include "common/map.h" #include "common/raw_string_ostream.h" #include "llvm/ADT/IntrusiveRefCntPtr.h" #include "llvm/ADT/StringRef.h" @@ -347,9 +348,12 @@ class CarbonExternalASTSource : public clang::ExternalASTSource { auto StartTranslationUnit(clang::ASTConsumer* consumer) -> void override; private: + auto MapInstIdToClangDecl(clang::DeclContext& decl_context, + LookupResult lookup) -> clang::NamedDecl*; + Check::Context* context_; clang::ASTContext* ast_context_; - clang::NamespaceDecl* carbon_cpp_namespace_ = nullptr; + Map scope_mapping; }; void CarbonExternalASTSource::StartTranslationUnit( @@ -361,24 +365,27 @@ void CarbonExternalASTSource::StartTranslationUnit( } // Map a Carbon entity to a Clang NamedDecl. -static auto MapInstIdToClangDecl(Context& context, - clang::ASTContext& ast_context, - clang::DeclContext& decl_context, - LookupResult lookup) -> clang::NamedDecl* { +auto CarbonExternalASTSource::MapInstIdToClangDecl( + clang::DeclContext& decl_context, LookupResult lookup) + -> clang::NamedDecl* { auto target_inst_id = lookup.scope_result.target_inst_id(); if (auto target_inst = - context.insts().TryGetAs(target_inst_id)) { - auto& name_scope = context.name_scopes().Get(target_inst->name_scope_id); + context_->insts().TryGetAs(target_inst_id)) { + auto& name_scope = context_->name_scopes().Get(target_inst->name_scope_id); auto* identifier_info = - GetClangIdentifierInfo(context, name_scope.name_id()); + GetClangIdentifierInfo(*context_, name_scope.name_id()); // TODO: Don't immediately use the decl_context - build any intermediate // namespaces iteratively. // Eventually add a mapping and use that/populate it/keep it up to date. // decl_context could be prepopulated in that mapping and not passed // explicitly to MapInstIdToClangDecl. - return clang::NamespaceDecl::Create( - ast_context, &decl_context, false, clang::SourceLocation(), + auto* namespace_decl = clang::NamespaceDecl::Create( + *ast_context_, &decl_context, false, clang::SourceLocation(), clang::SourceLocation(), identifier_info, nullptr, false); + scope_mapping.Insert(static_cast(namespace_decl), + target_inst_id); + namespace_decl->setHasExternalVisibleStorage(); + return namespace_decl; } return nullptr; } @@ -386,7 +393,10 @@ static auto MapInstIdToClangDecl(Context& context, auto CarbonExternalASTSource::FindExternalVisibleDeclsByName( const clang::DeclContext* decl_context, clang::DeclarationName decl_name, const clang::DeclContext* /*OriginalDC*/) -> bool { - if (decl_context != carbon_cpp_namespace_) { + auto decl_context_inst_id = + scope_mapping.Lookup(const_cast(decl_context)); + + if (!decl_context_inst_id) { if (decl_context->getDeclKind() != clang::Decl::Kind::TranslationUnit) { return false; } @@ -400,13 +410,15 @@ auto CarbonExternalASTSource::FindExternalVisibleDeclsByName( // Build the top level 'Carbon' namespace auto& ast_context = decl_context->getParentASTContext(); auto& mutable_tu_decl_context = *ast_context.getTranslationUnitDecl(); - carbon_cpp_namespace_ = clang::NamespaceDecl::Create( + auto* carbon_cpp_namespace = clang::NamespaceDecl::Create( ast_context, &mutable_tu_decl_context, false, clang::SourceLocation(), clang::SourceLocation(), &ast_context.Idents.get(carbon_namespace_name), nullptr, false); - carbon_cpp_namespace_->setHasExternalVisibleStorage(); + carbon_cpp_namespace->setHasExternalVisibleStorage(); + scope_mapping.Insert(static_cast(carbon_cpp_namespace), + SemIR::Namespace::PackageInstId); SetExternalVisibleDeclsForName(decl_context, decl_name, - {carbon_cpp_namespace_}); + {carbon_cpp_namespace}); return true; } @@ -418,7 +430,7 @@ auto CarbonExternalASTSource::FindExternalVisibleDeclsByName( // here - completeness should've been checked by clang before this point. if (!AppendLookupScopesForConstant( *context_, SemIR::LocId::None, - context_->constant_values().Get(SemIR::Namespace::PackageInstId), + context_->constant_values().Get(decl_context_inst_id.value()), SemIR::ConstantId::None, &lookup_scopes)) { return false; } @@ -441,8 +453,7 @@ auto CarbonExternalASTSource::FindExternalVisibleDeclsByName( } // Map the found Carbon entity to a Clang NamedDecl. - auto* clang_decl = MapInstIdToClangDecl(*context_, *ast_context_, - *carbon_cpp_namespace_, result); + auto* clang_decl = MapInstIdToClangDecl(*decl_context_inst_id.key(), result); if (!clang_decl) { return false; } diff --git a/toolchain/check/testdata/interop/cpp/reverse/simple.carbon b/toolchain/check/testdata/interop/cpp/reverse/simple.carbon index 7d64b27a1c16..b803a74d3f7c 100644 --- a/toolchain/check/testdata/interop/cpp/reverse/simple.carbon +++ b/toolchain/check/testdata/interop/cpp/reverse/simple.carbon @@ -10,23 +10,9 @@ // TIP: To dump output, run: // TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/reverse/simple.carbon -// --- fail_simple.carbon - -library "[[@TEST_NAME]]"; - -// Demonstrate that the 'Carbon' namespace has been injected into the C++ compilation. - -import Cpp inline ''' -// CHECK:STDERR: fail_simple.carbon:[[@LINE+4]]:9: error: no type named 'NonExistent' in namespace 'Carbon' [CppInteropParseError] -// CHECK:STDERR: 11 | Carbon::NonExistent v; -// CHECK:STDERR: | ~~~~~~~~^ -// CHECK:STDERR: -Carbon::NonExistent v; -'''; - - // --- other.carbon package Other; +namespace Nested; // --- namespace.carbon library "[[@TEST_NAME]]"; @@ -34,4 +20,5 @@ library "[[@TEST_NAME]]"; import Other; import Cpp inline ''' namespace X = Carbon::Other; +namespace Y = Carbon::Other::Nested; ''';