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Implement support for mixed-access overload sets. (#6137)

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This turns out to be quite important, as several important standard
library types (such as `std::string`) have mixed-access overload sets
for their constructors as an implementation detail. The overall approach
here is:

- Use the most permissive access to determine the access of the overload
set itself. This affects whether name lookup finds the member name at
all.
- After overload resolution, re-check the access of the selected member,
if it's protected or private.

---------

Co-authored-by: Dana Jansens <danakj@orodu.net>
This commit is contained in:
Richard Smith
2025-09-26 23:18:16 +00:00
committed by GitHub
co-authored by Dana Jansens
parent 83ba714165
commit 3b6d202730
11 changed files with 238 additions and 332 deletions
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toolchain/check/cpp/overload_resolution.cpp
+41 -2
View File
@@ -11,9 +11,12 @@
#include "toolchain/check/cpp/import.h"
#include "toolchain/check/cpp/location.h"
#include "toolchain/check/cpp/type_mapping.h"
#include "toolchain/check/member_access.h"
#include "toolchain/check/name_lookup.h"
#include "toolchain/diagnostics/diagnostic_emitter.h"
#include "toolchain/sem_ir/function.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/name_scope.h"
#include "toolchain/sem_ir/typed_insts.h"
namespace Carbon::Check {
@@ -79,6 +82,40 @@ static auto AddOverloadCandidataes(clang::Sema& sema,
}
}
// Checks whether a selected overload is accessible and diagnoses if not.
static auto CheckOverloadAccess(Context& context, SemIR::LocId loc_id,
const SemIR::CppOverloadSet& overload_set,
clang::DeclAccessPair overload,
SemIR::InstId overload_inst_id) -> void {
SemIR::AccessKind member_access_kind;
switch (overload->getAccess()) {
case clang::AS_none:
case clang::AS_public: {
return;
}
case clang::AS_protected: {
member_access_kind = SemIR::AccessKind::Protected;
break;
}
case clang::AS_private: {
member_access_kind = SemIR::AccessKind::Private;
break;
}
}
auto name_scope_const_id = context.constant_values().Get(
context.name_scopes().Get(overload_set.parent_scope_id).inst_id());
SemIR::AccessKind allowed_access_kind =
GetHighestAllowedAccess(context, loc_id, name_scope_const_id);
CheckAccess(context, loc_id, SemIR::LocId(overload_inst_id),
overload_set.name_id, member_access_kind,
/*is_parent_access=*/false,
{.constant_id = name_scope_const_id,
.highest_allowed_access = allowed_access_kind});
}
// Returns whether the decl is an operator member function.
static auto IsOperatorMethodDecl(clang::Decl* decl) -> bool {
auto* clang_method_decl = dyn_cast<clang::CXXMethodDecl>(decl);
@@ -136,12 +173,14 @@ static auto ResolveCalleeId(Context& context, SemIR::LocId loc_id,
// TODO: Handle the cases when Function is null.
CARBON_CHECK(best_viable_fn->Function);
sema.MarkFunctionReferenced(loc, best_viable_fn->Function);
SemIR::InstId result = ImportCppFunctionDecl(
SemIR::InstId result_id = ImportCppFunctionDecl(
context, loc_id, best_viable_fn->Function,
// If this is an operator method, the first arg will be used as self.
arg_exprs.size() -
(IsOperatorMethodDecl(best_viable_fn->Function) ? 1 : 0));
return result;
CheckOverloadAccess(context, loc_id, overload_set,
best_viable_fn->FoundDecl, result_id);
return result_id;
}
case clang::OverloadingResult::OR_No_Viable_Function: {
candidate_set.NoteCandidates(