Author: Haojian Wu Date: 2025-02-10T15:05:49+01:00 New Revision: 4d2a1bf563556d12cccc4cace1c2e225a3c002e4
URL: https://github.com/llvm/llvm-project/commit/4d2a1bf563556d12cccc4cace1c2e225a3c002e4 DIFF: https://github.com/llvm/llvm-project/commit/4d2a1bf563556d12cccc4cace1c2e225a3c002e4.diff LOG: [clang] CTAD alias: Respect explicit deduction guides defined after the first use of the alias template. (#125478) Fixes #103016 This is the last missing piece for the C++20 CTAD alias feature. No release note being added in this PR yet, I will send out a follow-up patch to mark this feature done. (Since the release 20 branch is cut, I think we should target on clang21). Added: Modified: clang/lib/Sema/SemaTemplateDeductionGuide.cpp clang/test/SemaCXX/cxx20-ctad-type-alias.cpp Removed: ################################################################################ diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp index 0d079677eecc568..e5931f4684a57d8 100644 --- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp +++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp @@ -740,6 +740,28 @@ bool hasDeclaredDeductionGuides(DeclarationName Name, DeclContext *DC) { return false; } +// Returns all source deduction guides associated with the declared +// deduction guides that have the specified deduction guide name. +llvm::DenseSet<const NamedDecl *> getSourceDeductionGuides(DeclarationName Name, + DeclContext *DC) { + assert(Name.getNameKind() == + DeclarationName::NameKind::CXXDeductionGuideName && + "name must be a deduction guide name"); + llvm::DenseSet<const NamedDecl *> Result; + for (auto *D : DC->lookup(Name)) { + if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D)) + D = FTD->getTemplatedDecl(); + + if (const auto *GD = dyn_cast<CXXDeductionGuideDecl>(D)) { + assert(GD->getSourceDeductionGuide() && + "deduction guide for alias template must have a source deduction " + "guide"); + Result.insert(GD->getSourceDeductionGuide()); + } + } + return Result; +} + // Build the associated constraints for the alias deduction guides. // C++ [over.match.class.deduct]p3.3: // The associated constraints ([temp.constr.decl]) are the conjunction of the @@ -1191,17 +1213,14 @@ void DeclareImplicitDeductionGuidesForTypeAlias( if (AliasTemplate->isInvalidDecl()) return; auto &Context = SemaRef.Context; - // FIXME: if there is an explicit deduction guide after the first use of the - // type alias usage, we will not cover this explicit deduction guide. fix this - // case. - if (hasDeclaredDeductionGuides( - Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate), - AliasTemplate->getDeclContext())) - return; auto [Template, AliasRhsTemplateArgs] = getRHSTemplateDeclAndArgs(SemaRef, AliasTemplate); if (!Template) return; + auto SourceDeductionGuides = getSourceDeductionGuides( + Context.DeclarationNames.getCXXDeductionGuideName(AliasTemplate), + AliasTemplate->getDeclContext()); + DeclarationNameInfo NameInfo( Context.DeclarationNames.getCXXDeductionGuideName(Template), Loc); LookupResult Guides(SemaRef, NameInfo, clang::Sema::LookupOrdinaryName); @@ -1210,6 +1229,8 @@ void DeclareImplicitDeductionGuidesForTypeAlias( for (auto *G : Guides) { if (auto *DG = dyn_cast<CXXDeductionGuideDecl>(G)) { + if (SourceDeductionGuides.contains(DG)) + continue; // The deduction guide is a non-template function decl, we just clone it. auto *FunctionType = SemaRef.Context.getTrivialTypeSourceInfo(DG->getType()); @@ -1252,7 +1273,7 @@ void DeclareImplicitDeductionGuidesForTypeAlias( continue; } FunctionTemplateDecl *F = dyn_cast<FunctionTemplateDecl>(G); - if (!F) + if (!F || SourceDeductionGuides.contains(F->getTemplatedDecl())) continue; // The **aggregate** deduction guides are handled in a diff erent code path // (DeclareAggregateDeductionGuideFromInitList), which involves the tricky diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp index 2d43e46b9e3d76b..37dca2215af6ba3 100644 --- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp +++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp @@ -234,11 +234,23 @@ int i = 0; AFoo s{i}; static_assert(__is_same(decltype(s.t), int)); +template<class T> +using BFoo = AFoo<T>; + +// template explicit deduction guide. +template<class T> +Foo(T) -> Foo<float>; +static_assert(__is_same(decltype(AFoo(i).t), float)); +static_assert(__is_same(decltype(BFoo(i).t), float)); + // explicit deduction guide. Foo(int) -> Foo<X>; -AFoo s2{i}; -// FIXME: the type should be X because of the above explicit deduction guide. -static_assert(__is_same(decltype(s2.t), int)); +static_assert(__is_same(decltype(AFoo(i).t), X)); +static_assert(__is_same(decltype(BFoo(i).t), X)); + +Foo(double) -> Foo<int>; +static_assert(__is_same(decltype(AFoo(1.0).t), int)); +static_assert(__is_same(decltype(BFoo(1.0).t), int)); } // namespace test16 namespace test17 { _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
