Author: Corentin Jabot Date: 2025-11-26T19:18:36+01:00 New Revision: c98e867822d8e741159ff0be09ccc2a5c7841a28
URL: https://github.com/llvm/llvm-project/commit/c98e867822d8e741159ff0be09ccc2a5c7841a28 DIFF: https://github.com/llvm/llvm-project/commit/c98e867822d8e741159ff0be09ccc2a5c7841a28.diff LOG: [Clang] Fix false positive -Wignored-qualifiers (#169664) A deduced return type can be an object type, in which case `const` can have an effect. Delay the diagnostic to the point at which the type is deduced. Add tests for lambdas. Fixes #43054 Note that there is a discussion in #43054 about adding a separate warning for "const return types are weird" for the class type cases, but it would have to be a separate warning - warning which currently exists in clang-tidy as `readability-const-return-type`. Added: Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaStmt.cpp clang/lib/Sema/SemaType.cpp clang/test/SemaCXX/return.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 408b7580643d6..66bc603252ddf 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -396,6 +396,7 @@ Improvements to Clang's diagnostics - Fixed false positives in ``-Waddress-of-packed-member`` diagnostics when potential misaligned members get processed before they can get discarded. (#GH144729) +- Fix a false positive warning in ``-Wignored-qualifiers`` when the return type is undeduced. (#GH43054) - Clang now emits a diagnostic with the correct message in case of assigning to const reference captured in lambda. (#GH105647) diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp index 655fa31bbf5c7..6bb1a27d1800c 100644 --- a/clang/lib/Sema/SemaStmt.cpp +++ b/clang/lib/Sema/SemaStmt.cpp @@ -3889,6 +3889,11 @@ bool Sema::DeduceFunctionTypeFromReturnExpr(FunctionDecl *FD, // Update all declarations of the function to have the deduced return type. Context.adjustDeducedFunctionResultType(FD, Deduced); + if (!Deduced->isDependentType() && !Deduced->isRecordType() && + !FD->isFunctionTemplateSpecialization()) + diagnoseIgnoredQualifiers( + diag::warn_qual_return_type, + FD->getDeclaredReturnType().getLocalCVRQualifiers(), FD->getLocation()); return false; } diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp index eb8b1352d1be1..eaf95a8371c2f 100644 --- a/clang/lib/Sema/SemaType.cpp +++ b/clang/lib/Sema/SemaType.cpp @@ -5067,8 +5067,11 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state, // cv-qualifiers on return types are pointless except when the type is a // class type in C++. if ((T.getCVRQualifiers() || T->isAtomicType()) && + // A dependent type or an undeduced type might later become a class + // type. !(S.getLangOpts().CPlusPlus && - (T->isDependentType() || T->isRecordType()))) { + (T->isRecordType() || T->isDependentType() || + T->isUndeducedAutoType()))) { if (T->isVoidType() && !S.getLangOpts().CPlusPlus && D.getFunctionDefinitionKind() == FunctionDefinitionKind::Definition) { diff --git a/clang/test/SemaCXX/return.cpp b/clang/test/SemaCXX/return.cpp index 796c9ae91dedc..92be66c24489e 100644 --- a/clang/test/SemaCXX/return.cpp +++ b/clang/test/SemaCXX/return.cpp @@ -1,4 +1,5 @@ // RUN: %clang_cc1 %s -std=c++11 -fcxx-exceptions -fexceptions -fsyntax-only -Wignored-qualifiers -verify +// RUN: %clang_cc1 %s -std=c++14 -fcxx-exceptions -fexceptions -fsyntax-only -Wignored-qualifiers -verify int test1() { throw; @@ -132,3 +133,27 @@ void cxx_unresolved_expr() { // expr doesn't assert. return int(undeclared, 4; // expected-error {{use of undeclared identifier 'undeclared'}} } + +#if __cplusplus >= 201402L +namespace GH43054 { +struct S{}; +const auto foo() { return 0; } // expected-warning {{'const' type qualifier on return type has no effect}} +const auto bar() { return S{}; } +template <typename T> +const auto baz() { return T{}; } + +void test() { + baz<int>(); + baz<S>(); + + []() -> const auto { // expected-warning {{'const' type qualifier on return type has no effect}} + return 0; + }(); + + []() -> const auto { + return S{}; + }(); +} +} + +#endif _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
