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Support indirect imports of namespaces. (#7122)

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When a namespace that was imported from C++ is indirectly imported, find
the corresponding namespace in the current C++ AST and return that
instead. This namespace may have completely different contents than the
one we found before; that's fine. The current file's view of a namespace
depends on what it imported.

Assisted-by: Gemini via Antigravity
This commit is contained in:
Richard Smith
2026-04-28 23:55:18 +00:00
committed by GitHub
parent 7bb86bad66
commit ab0aff91b8
5 changed files with 202 additions and 59 deletions
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toolchain/check/cpp/import.cpp
+45 -20
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@@ -150,6 +150,22 @@ auto ImportCpp(Context& context,
}
}
// Returns whether the current context has any C++ imports. If not, produces a
// suitable diagnostic.
static auto CheckForCppContextForIndirectImport(Context& context,
SemIR::LocId loc_id) -> bool {
// TODO: We should perform cross-file imports by importing the C++ AST. For
// now we require the C++ declaration to already be imported into the
// destination file, and find the corresponding declaration there and import
// that.
if (!context.cpp_context()) {
context.TODO(
loc_id, "indirect import of C++ declaration with no direct Cpp import");
return false;
}
return true;
}
// NOLINTNEXTLINE(misc-no-recursion)
static auto FindCorrespondingType(Context& context, SemIR::LocId loc_id,
clang::QualType type) -> clang::QualType;
@@ -236,6 +252,29 @@ static auto FindCorrespondingDecl(Context& context, SemIR::LocId loc_id,
return nullptr;
}
auto FindCorrespondingClangDeclKey(Context& context, SemIR::LocId loc_id,
const SemIR::File& file,
SemIR::ClangDeclId clang_decl_id)
-> std::optional<SemIR::ClangDeclKey> {
if (!CheckForCppContextForIndirectImport(context, loc_id)) {
return std::nullopt;
}
CARBON_CHECK(clang_decl_id.has_value());
auto key = file.clang_decls().Get(clang_decl_id).key;
const auto* decl = key.decl;
auto* corresponding = FindCorrespondingDecl(context, loc_id, decl);
if (!corresponding) {
// TODO: This needs a proper diagnostic.
context.TODO(
loc_id,
"use of imported C++ declaration with no corresponding local import");
return std::nullopt;
}
key.decl = corresponding;
return key;
}
// Given a type in some C++ AST which is *not* expected to be `context`,
// find the corresponding type in `context`, if there is one.
// NOLINTNEXTLINE(misc-no-recursion)
@@ -277,23 +316,15 @@ auto ImportCppDeclFromFile(Context& context, SemIR::LocId loc_id,
const SemIR::File& file,
SemIR::ClangDeclId clang_decl_id)
-> SemIR::ConstantId {
CARBON_CHECK(clang_decl_id.has_value());
auto key = file.clang_decls().Get(clang_decl_id).key;
const auto* decl = key.decl;
auto* corresponding = FindCorrespondingDecl(context, loc_id, decl);
if (!corresponding) {
// TODO: This needs a proper diagnostic.
context.TODO(
loc_id,
"use of imported C++ declaration with no corresponding local import");
auto key =
FindCorrespondingClangDeclKey(context, loc_id, file, clang_decl_id);
if (!key) {
return SemIR::ErrorInst::ConstantId;
}
key.decl = corresponding;
auto imported_inst_id = ImportCppDecl(context, loc_id, key);
auto imported_inst_id = ImportCppDecl(context, loc_id, *key);
auto imported_const_id = context.constant_values().Get(imported_inst_id);
if (!imported_const_id.is_constant()) {
context.TODO(loc_id, "imported C++ declant is not constant");
context.TODO(loc_id, "imported C++ declaration is not constant");
return SemIR::ErrorInst::ConstantId;
}
return imported_const_id;
@@ -302,13 +333,7 @@ auto ImportCppDeclFromFile(Context& context, SemIR::LocId loc_id,
auto ImportCppConstantFromFile(Context& context, SemIR::LocId loc_id,
const SemIR::File& file, SemIR::InstId inst_id)
-> SemIR::ConstantId {
// TODO: We should perform cross-file imports by importing the C++ AST. For
// now we require the C++ declaration to already be imported into the
// destination file, and find the corresponding declaration there and import
// that.
if (!context.cpp_context()) {
context.TODO(
loc_id, "indirect import of C++ declaration with no direct Cpp import");
if (!CheckForCppContextForIndirectImport(context, loc_id)) {
return SemIR::ErrorInst::ConstantId;
}