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When importing a looked up name, reuse previously imported declaration instead of importing the same declaration again (#5789)

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Added test coverage to demonstrate name lookup following import of a
type of a function parameter.
SemIR changes show that the same decl isn't imported multiple times.

Part of #5533.
This commit is contained in:
Boaz Brickner
2025-07-16 11:21:49 +00:00
committed by GitHub
parent f204bdf094
commit 4f8d0649d5
7 changed files with 142 additions and 48 deletions
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toolchain/check/import_cpp.cpp
+41 -17
View File
@@ -38,6 +38,7 @@
#include "toolchain/diagnostics/diagnostic_emitter.h"
#include "toolchain/diagnostics/format_providers.h"
#include "toolchain/parse/node_ids.h"
#include "toolchain/sem_ir/clang_decl.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/name_scope.h"
#include "toolchain/sem_ir/typed_insts.h"
@@ -462,8 +463,21 @@ static auto ClangLookup(Context& context, SemIR::NameScopeId scope_id,
return lookup;
}
// If `decl` already mapped to an instruction, returns that instruction.
// Otherwise returns `None`.
static auto LookupClangDeclInstId(Context& context, clang::Decl* decl)
-> SemIR::InstId {
auto& clang_decls = context.sem_ir().clang_decls();
if (auto context_clang_decl_id = clang_decls.Lookup(decl);
context_clang_decl_id.has_value()) {
return clang_decls.Get(context_clang_decl_id).inst_id;
}
return SemIR::InstId::None;
}
// Imports a namespace declaration from Clang to Carbon. If successful, returns
// the new Carbon namespace declaration `InstId`.
// the new Carbon namespace declaration `InstId`. If the declaration was already
// imported, returns the mapped instruction.
static auto ImportNamespaceDecl(Context& context,
SemIR::NameScopeId parent_scope_id,
SemIR::NameId name_id,
@@ -484,15 +498,17 @@ static auto AsCarbonNamespace(Context& context,
clang::DeclContext* decl_context)
-> SemIR::InstId {
CARBON_CHECK(decl_context);
auto& clang_decls = context.sem_ir().clang_decls();
// Check if the decl context is already mapped to a Carbon namespace.
if (auto context_clang_decl_id =
clang_decls.Lookup(clang::dyn_cast<clang::Decl>(decl_context));
context_clang_decl_id.has_value()) {
return clang_decls.Get(context_clang_decl_id).inst_id;
// Check if the declaration is already mapped.
// TODO: Try to avoid this check by rotating the loops below so they treat the
// given decl_context the same at its enclosing contexts.
if (SemIR::InstId existing_inst_id = LookupClangDeclInstId(
context, clang::dyn_cast<clang::Decl>(decl_context));
existing_inst_id.has_value()) {
return existing_inst_id;
}
auto& clang_decls = context.sem_ir().clang_decls();
// We know we have at least one context to map, add all decl contexts we need
// to map.
llvm::SmallVector<clang::DeclContext*> decl_contexts;
@@ -681,12 +697,9 @@ static auto MapRecordType(Context& context, SemIR::LocId loc_id,
return {.inst_id = SemIR::TypeInstId::None, .type_id = SemIR::TypeId::None};
}
auto& clang_decls = context.sem_ir().clang_decls();
SemIR::InstId record_inst_id = SemIR::InstId::None;
if (auto record_clang_decl_id = clang_decls.Lookup(record_decl);
record_clang_decl_id.has_value()) {
record_inst_id = clang_decls.Get(record_clang_decl_id).inst_id;
} else {
// Check if the declaration is already mapped.
SemIR::InstId record_inst_id = LookupClangDeclInstId(context, record_decl);
if (!record_inst_id.has_value()) {
auto parent_inst_id =
AsCarbonNamespace(context, record_decl->getDeclContext());
auto parent_name_scope_id =
@@ -1041,12 +1054,20 @@ static auto CreateFunctionParamsInsts(Context& context, SemIR::LocId loc_id,
}
// Imports a function declaration from Clang to Carbon. If successful, returns
// the new Carbon function declaration `InstId`.
// the new Carbon function declaration `InstId`. If the declaration was already
// imported, returns the mapped instruction.
static auto ImportFunctionDecl(Context& context, SemIR::LocId loc_id,
SemIR::NameScopeId scope_id,
SemIR::NameId name_id,
clang::FunctionDecl* clang_decl)
-> SemIR::InstId {
// Check if the declaration is already mapped.
if (SemIR::InstId existing_inst_id =
LookupClangDeclInstId(context, clang_decl);
existing_inst_id.has_value()) {
return existing_inst_id;
}
if (clang_decl->isVariadic()) {
context.TODO(loc_id, "Unsupported: Variadic function");
MarkFailedDecl(context, clang_decl);
@@ -1114,6 +1135,9 @@ static auto ImportFunctionDecl(Context& context, SemIR::LocId loc_id,
}
// Imports a declaration from Clang to Carbon. If successful, returns the
// instruction for the new Carbon declaration.
// TODO: Remove `scope_id` parameter since we the scope the name was found in
// isn't necessarily the parent scope. See
// https://github.com/carbon-language/carbon-lang/pull/5789/files/a5629ebb303c5b1aef46181eb860b7065ca1aaf1#r2201769611
static auto ImportNameDecl(Context& context, SemIR::LocId loc_id,
SemIR::NameScopeId scope_id, SemIR::NameId name_id,
clang::NamedDecl* clang_decl) -> SemIR::InstId {
@@ -1123,8 +1147,8 @@ static auto ImportNameDecl(Context& context, SemIR::LocId loc_id,
}
if (auto* clang_namespace_decl =
clang::dyn_cast<clang::NamespaceDecl>(clang_decl)) {
return ImportNamespaceDecl(context, scope_id, name_id,
clang_namespace_decl);
return AsCarbonNamespace(
context, llvm::dyn_cast<clang::DeclContext>(clang_namespace_decl));
}
if (auto* type_decl = clang::dyn_cast<clang::TypeDecl>(clang_decl)) {
auto type = type_decl->getASTContext().getTypeDeclType(type_decl);