llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Krystian Stasiowski (sdkrystian) <details> <summary>Changes</summary> According to [[expr.prim.id.qual] p3](http://eel.is/c++draft/expr.prim.id.qual#<!-- -->3): > The _nested-name-specifier_ `:`: nominates the global namespace. A _nested-name-specifier_ with a _computed-type-specifier_ nominates the type denoted by the _computed-type-specifier_, which shall be a class or enumeration type. **If a _nested-name-specifier_ `N` is declarative and has a _simple-template-id_ with a template argument list `A` that involves a template parameter, let `T` be the template nominated by `N` without `A`. `T` shall be a class template.** Meaning, the out-of-line definition of `A::f` in the following example is ill-formed: ```cpp template<typename T> struct A { void f(); }; template<typename T> using B = A<T>; template<typename T> void B<T>::f() { } // error: a declarative nested name specifier cannot name a type alias template ``` This patch diagnoses such cases as an extension (in group `alias-template-in-declaration-name`). --- Full diff: https://github.com/llvm/llvm-project/pull/80842.diff 4 Files Affected: - (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (+3) - (modified) clang/lib/Sema/SemaDecl.cpp (+26-10) - (added) clang/test/CXX/expr/expr.prim/expr.prim.id/expr.prim.id.qual/p3.cpp (+29) - (modified) clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p1.cpp (+1-1) ``````````diff diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td index f76e7a3392183..d02fddd069341 100644 --- a/clang/include/clang/Basic/DiagnosticSemaKinds.td +++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td @@ -8250,6 +8250,9 @@ def err_not_tag_in_scope : Error< def ext_template_after_declarative_nns : ExtWarn< "'template' cannot be used after a declarative nested name specifier">, InGroup<DiagGroup<"template-in-declaration-name">>; +def ext_alias_template_in_declarative_nns : ExtWarn< + "a declarative nested name specifier cannot name an alias template">, + InGroup<DiagGroup<"alias-template-in-declaration-name">>; def err_no_typeid_with_fno_rtti : Error< "use of typeid requires -frtti">; diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 481d952d2389b..464f3738b0ba5 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -6207,6 +6207,8 @@ bool Sema::diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC, SourceLocation Loc, TemplateIdAnnotation *TemplateId, bool IsMemberSpecialization) { + assert(SS.isValid() && "diagnoseQualifiedDeclaration called for declaration " + "without nested-name-specifier"); DeclContext *Cur = CurContext; while (isa<LinkageSpecDecl>(Cur) || isa<CapturedDecl>(Cur)) Cur = Cur->getParent(); @@ -6295,22 +6297,36 @@ bool Sema::diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC, << FixItHint::CreateRemoval(TemplateId->TemplateKWLoc); NestedNameSpecifierLoc SpecLoc(SS.getScopeRep(), SS.location_data()); - while (SpecLoc.getPrefix()) { + do { if (SpecLoc.getNestedNameSpecifier()->getKind() == NestedNameSpecifier::TypeSpecWithTemplate) Diag(Loc, diag::ext_template_after_declarative_nns) << FixItHint::CreateRemoval( SpecLoc.getTypeLoc().getTemplateKeywordLoc()); - SpecLoc = SpecLoc.getPrefix(); - } - // C++11 [dcl.meaning]p1: - // [...] "The nested-name-specifier of the qualified declarator-id shall - // not begin with a decltype-specifer" - if (isa_and_nonnull<DecltypeType>( - SpecLoc.getNestedNameSpecifier()->getAsType())) - Diag(Loc, diag::err_decltype_in_declarator) - << SpecLoc.getTypeLoc().getSourceRange(); + if (const Type *T = SpecLoc.getNestedNameSpecifier()->getAsType()) { + if (const auto *TST = T->getAsAdjusted<TemplateSpecializationType>()) { + // C++23 [expr.prim.id.qual]p3: + // [...] If a nested-name-specifier N is declarative and has a + // simple-template-id with a template argument list A that involves a + // template parameter, let T be the template nominated by N without A. + // T shall be a class template. + if (TST->isDependentType() && TST->isTypeAlias()) + Diag(Loc, diag::ext_alias_template_in_declarative_nns) + << SpecLoc.getLocalSourceRange(); + } else if (T->isDecltypeType()) { + // C++23 [expr.prim.id.qual]p2: + // [...] A declarative nested-name-specifier shall not have a + // decltype-specifier. + // + // FIXME: This wording appears to be defective, as it does not + // forbid declarative nested-name-specifiers that begin with a + // pack-index-specifier. + Diag(Loc, diag::err_decltype_in_declarator) + << SpecLoc.getTypeLoc().getSourceRange(); + } + } + } while ((SpecLoc = SpecLoc.getPrefix())); return false; } diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.id/expr.prim.id.qual/p3.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.id/expr.prim.id.qual/p3.cpp new file mode 100644 index 0000000000000..ba89d2c96c7bb --- /dev/null +++ b/clang/test/CXX/expr/expr.prim/expr.prim.id/expr.prim.id.qual/p3.cpp @@ -0,0 +1,29 @@ +// RUN: %clang_cc1 -verify %s + +template<typename T> +struct A { + void f(); +}; + +template<typename T> +using B = A<T>; + +template<typename T> +void B<T>::f() { } // expected-warning {{a declarative nested name specifier cannot name an alias template}} + +template<> +void B<int>::f() { } // ok, template argument list of simple-template-id doesn't involve template parameters + +namespace N { + + template<typename T> + struct D { + void f(); + }; + + template<typename T> + using E = C<T>; +} + +template<typename T> +void N::E<T>::f() { } // expected-warning {{a declarative nested name specifier cannot name an alias template}} diff --git a/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p1.cpp b/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p1.cpp index 82983f05fe878..910dab11ee5e1 100644 --- a/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p1.cpp +++ b/clang/test/CXX/temp/temp.res/temp.dep/temp.dep.type/p1.cpp @@ -26,5 +26,5 @@ namespace Example2 { void g(); }; template<class T> using B = A<T>; - template<class T> void B<T>::g() {} // ok. + template<class T> void B<T>::g() {} // // expected-warning {{a declarative nested name specifier cannot name an alias template}} } `````````` </details> https://github.com/llvm/llvm-project/pull/80842 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits