https://github.com/cor3ntin updated https://github.com/llvm/llvm-project/pull/169664
>From 78ad723f5e33cbed36f24ccb1d0464536ace845a Mon Sep 17 00:00:00 2001 From: Corentin Jabot <[email protected]> Date: Wed, 26 Nov 2025 16:11:41 +0100 Subject: [PATCH 1/2] [Clang] Fix false positive -Wignored-qualifiers 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 --- clang/docs/ReleaseNotes.rst | 1 + clang/lib/Sema/SemaStmt.cpp | 5 +++++ clang/lib/Sema/SemaType.cpp | 3 ++- clang/test/SemaCXX/return.cpp | 25 +++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 8161ccdffca82..c43bf2c7ff99a 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -392,6 +392,7 @@ 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..3a8dd9df60827 100644 --- a/clang/lib/Sema/SemaType.cpp +++ b/clang/lib/Sema/SemaType.cpp @@ -5068,7 +5068,8 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state, // class type in C++. if ((T.getCVRQualifiers() || T->isAtomicType()) && !(S.getLangOpts().CPlusPlus && - (T->isDependentType() || T->isRecordType()))) { + (T->isDependentType() || T->isRecordType() || + 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 >From 1117fb1a9387aee9e799a83f3380e1091d544a62 Mon Sep 17 00:00:00 2001 From: Corentin Jabot <[email protected]> Date: Wed, 26 Nov 2025 17:14:46 +0100 Subject: [PATCH 2/2] add comment --- clang/lib/Sema/SemaType.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp index 3a8dd9df60827..e0a80b0d3a0dd 100644 --- a/clang/lib/Sema/SemaType.cpp +++ b/clang/lib/Sema/SemaType.cpp @@ -5067,8 +5067,9 @@ 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() == _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
