Author: Younan Zhang Date: 2024-04-01T14:47:15-07:00 New Revision: 76c721994a11abe898848699ea82da267ebc8320
URL: https://github.com/llvm/llvm-project/commit/76c721994a11abe898848699ea82da267ebc8320 DIFF: https://github.com/llvm/llvm-project/commit/76c721994a11abe898848699ea82da267ebc8320.diff LOG: [clang][Sema] Fix a CTAD regression after 42239d2e9 (#86914) The most recent declaration of a template as a friend can introduce a different template parameter depth compared to what we anticipate from a CTAD guide. Fixes https://github.com/llvm/llvm-project/issues/86769 Added: Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaTemplate.cpp clang/test/SemaTemplate/concepts-friends.cpp clang/test/SemaTemplate/ctad.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index d4401a43c123e7..ebeb47a871e27b 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -1106,6 +1106,10 @@ Bug Fixes to C++ Support - Fix a crash when an unresolved overload set is encountered on the RHS of a ``.*`` operator. (`#53815 <https://github.com/llvm/llvm-project/issues/53815>`_) +- Fixed a regression in CTAD that a friend declaration that befriends itself may cause + incorrect constraint substitution. + (`#86769 <https://github.com/llvm/llvm-project/issues/86769>`_) + Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ - Fixed an import failure of recursive friend class template. diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index a381d876a54c67..b619f5d729e86b 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -1830,7 +1830,27 @@ static TemplateParameterList *GetTemplateParameterList(TemplateDecl *TD) { // Make sure we get the template parameter list from the most // recent declaration, since that is the only one that is guaranteed to // have all the default template argument information. - return cast<TemplateDecl>(TD->getMostRecentDecl())->getTemplateParameters(); + Decl *D = TD->getMostRecentDecl(); + // C++11 [temp.param]p12: + // A default template argument shall not be specified in a friend class + // template declaration. + // + // Skip past friend *declarations* because they are not supposed to contain + // default template arguments. Moreover, these declarations may introduce + // template parameters living in diff erent template depths than the + // corresponding template parameters in TD, causing unmatched constraint + // substitution. + // + // FIXME: Diagnose such cases within a class template: + // template <class T> + // struct S { + // template <class = void> friend struct C; + // }; + // template struct S<int>; + while (D->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None && + D->getPreviousDecl()) + D = D->getPreviousDecl(); + return cast<TemplateDecl>(D)->getTemplateParameters(); } DeclResult Sema::CheckClassTemplate( diff --git a/clang/test/SemaTemplate/concepts-friends.cpp b/clang/test/SemaTemplate/concepts-friends.cpp index 255b0858917fb6..0b008811f13621 100644 --- a/clang/test/SemaTemplate/concepts-friends.cpp +++ b/clang/test/SemaTemplate/concepts-friends.cpp @@ -478,3 +478,29 @@ template <Concept> class Foo { }; } // namespace FriendOfFriend + +namespace GH86769 { + +template <typename T> +concept X = true; + +template <X T> struct Y { + Y(T) {} + template <X U> friend struct Y; + template <X U> friend struct Y; + template <X U> friend struct Y; +}; + +template <class T> +struct Z { + // FIXME: This is ill-formed per C++11 [temp.param]p12: + // A default template argument shall not be specified in a friend class + // template declaration. + template <X U = void> friend struct Y; +}; + +template struct Y<int>; +template struct Z<int>; +Y y(1); + +} diff --git a/clang/test/SemaTemplate/ctad.cpp b/clang/test/SemaTemplate/ctad.cpp index 388ed7d4cced18..ec144d4f44ba8c 100644 --- a/clang/test/SemaTemplate/ctad.cpp +++ b/clang/test/SemaTemplate/ctad.cpp @@ -53,4 +53,4 @@ X x; template<class T, class B> struct Y { Y(T); }; template<class T, class B=void> struct Y ; Y y(1); -}; +} _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
