https://github.com/zyn0217 created https://github.com/llvm/llvm-project/pull/134807
It's possible that some deduced template arguments come from default arguments, not just from the return type. So we need to recursively visit the default arguments of the parameter if it's referenced, thereby the template parameter referenced by the defualt arguments could come along to the synthesized deduction guide. Fixes https://github.com/llvm/llvm-project/issues/133132 >From d93117d955ba3a94c68cba1ec968662ae2eed572 Mon Sep 17 00:00:00 2001 From: Younan Zhang <zyn7...@gmail.com> Date: Tue, 8 Apr 2025 16:16:53 +0800 Subject: [PATCH] [Clang] Handle default template arguments for alias CTAD guides It's possible that some deduced template arguments come from default arguments, not just from the return type. So we need to recursively visit the default arguments if the parameter is referenced, thereby the template parameter referenced by the defualt arguments could come along to the synthesized deduction guide. --- clang/docs/ReleaseNotes.rst | 1 + clang/lib/Sema/SemaTemplateDeductionGuide.cpp | 17 ++++++++ clang/test/SemaTemplate/deduction-guide.cpp | 39 +++++++++++++++++++ 3 files changed, 57 insertions(+) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 5217e04b5e83f..a914657731dba 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -384,6 +384,7 @@ Bug Fixes to C++ Support - Clang no longer crashes when trying to unify the types of arrays with certain differences in qualifiers (this could happen during template argument deduction or when building a ternary operator). (#GH97005) +- Fixed type alias CTAD issues involving default template arguments. (#GH133132) - The initialization kind of elements of structured bindings direct-list-initialized from an array is corrected to direct-initialization. - Clang no longer crashes when a coroutine is declared ``[[noreturn]]``. (#GH127327) diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp index b4863cefc3fb4..30376ca774384 100644 --- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp +++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp @@ -690,6 +690,23 @@ SmallVector<unsigned> TemplateParamsReferencedInTemplateArgumentList( SemaRef.MarkUsedTemplateParameters( DeducedArgs, TemplateParamsList->getDepth(), ReferencedTemplateParams); + auto MarkDefaultArgs = [&](auto *Param) { + if (!Param || !Param->hasDefaultArgument()) + return; + SemaRef.MarkUsedTemplateParameters( + Param->getDefaultArgument().getArgument(), + TemplateParamsList->getDepth(), ReferencedTemplateParams); + }; + + for (unsigned Index = 0; Index < TemplateParamsList->size(); ++Index) { + if (!ReferencedTemplateParams[Index]) + continue; + auto *Param = TemplateParamsList->getParam(Index); + MarkDefaultArgs(dyn_cast<TemplateTypeParmDecl>(Param)); + MarkDefaultArgs(dyn_cast<NonTypeTemplateParmDecl>(Param)); + MarkDefaultArgs(dyn_cast<TemplateTemplateParmDecl>(Param)); + } + SmallVector<unsigned> Results; for (unsigned Index = 0; Index < TemplateParamsList->size(); ++Index) { if (ReferencedTemplateParams[Index]) diff --git a/clang/test/SemaTemplate/deduction-guide.cpp b/clang/test/SemaTemplate/deduction-guide.cpp index 6db132ca37c7e..76b6cb051b7dd 100644 --- a/clang/test/SemaTemplate/deduction-guide.cpp +++ b/clang/test/SemaTemplate/deduction-guide.cpp @@ -771,3 +771,42 @@ D d(24); // CHECK-NEXT: `-ParmVarDecl {{.+}} 'U' } // namespace GH132616_DeductionGuide + +namespace GH133132 { + +template <class _Ty> +struct A {}; + +template <class T = int, class U = T> +using AA = A<U>; + +AA a{}; + +// CHECK-LABEL: Dumping GH133132::<deduction guide for AA>: +// CHECK-NEXT: FunctionTemplateDecl {{.+}} implicit <deduction guide for AA> +// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} class depth 0 index 0 T +// CHECK-NEXT: | `-TemplateArgument type 'int' +// CHECK-NEXT: | `-BuiltinType {{.+}} 'int' +// CHECK-NEXT: |-TemplateTypeParmDecl {{.+}} class depth 0 index 1 U +// CHECK-NEXT: | `-TemplateArgument type 'T':'type-parameter-0-0' +// CHECK-NEXT: | `-TemplateTypeParmType {{.+}} 'T' dependent depth 0 index 0 +// CHECK-NEXT: | `-TemplateTypeParm {{.+}} 'T' +// CHECK-NEXT: |-TypeTraitExpr {{.+}} 'bool' __is_deducible +// CHECK-NEXT: | |-DeducedTemplateSpecializationType {{.+}} 'GH133132::AA' dependent +// CHECK-NEXT: | | `-name: 'GH133132::AA' +// CHECK-NEXT: | | `-TypeAliasTemplateDecl {{.+}} AA +// CHECK-NEXT: | `-TemplateSpecializationType {{.+}} 'A<U>' dependent +// CHECK-NEXT: | |-name: 'A':'GH133132::A' qualified +// CHECK-NEXT: | | `-ClassTemplateDecl {{.+}} A +// CHECK-NEXT: | `-TemplateArgument type 'U':'type-parameter-0-1' +// CHECK-NEXT: | `-SubstTemplateTypeParmType {{.+}} 'U' sugar dependent class depth 0 index 0 _Ty +// CHECK-NEXT: | |-FunctionTemplate {{.+}} '<deduction guide for A>' +// CHECK-NEXT: | `-TemplateTypeParmType {{.+}} 'U' dependent depth 0 index 1 +// CHECK-NEXT: | `-TemplateTypeParm {{.+}} 'U' +// CHECK-NEXT: |-CXXDeductionGuideDecl {{.+}} implicit <deduction guide for AA> 'auto () -> A<U>' +// CHECK-NEXT: `-CXXDeductionGuideDecl {{.+}} implicit used <deduction guide for AA> 'auto () -> A<int>' implicit_instantiation +// CHECK-NEXT: |-TemplateArgument type 'int' +// CHECK-NEXT: | `-BuiltinType {{.+}} 'int' +// CHECK-NEXT: `-TemplateArgument type 'int' +// CHECK-NEXT: `-BuiltinType {{.+}} 'int' +} _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
