https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/86914
>From b31ca786d937dc180ad02042132596b2e5f3710f Mon Sep 17 00:00:00 2001 From: Younan Zhang <zyn7...@gmail.com> Date: Thu, 28 Mar 2024 14:13:12 +0800 Subject: [PATCH 1/2] [clang][Sema] Fix a CTAD regression after 42239d2e9 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 --- clang/docs/ReleaseNotes.rst | 3 +++ clang/lib/Sema/SemaTemplate.cpp | 14 +++++++++++- clang/test/SemaTemplate/concepts-friends.cpp | 24 ++++++++++++++++++++ clang/test/SemaTemplate/ctad.cpp | 2 +- 4 files changed, 41 insertions(+), 2 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 7fbe2fec6ca065..ed0996bd3d30c0 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -345,6 +345,9 @@ Bug Fixes in This Version - Fixes an assertion failure on invalid code when trying to define member functions in lambdas. +- Fixed a regression in CTAD that a friend declaration that befriends itself may cause + incorrect constraint substitution. (#GH86769). + Bug Fixes to Compiler Builtins ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index 005529a53270c3..14fabe36eee794 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -1836,7 +1836,19 @@ 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 *ND = TD->getMostRecentDecl(); + // Skip past friend Decls because they are not supposed to contain default + // template arguments. Moreover, these declarations may introduce template + // parameters living in different template depths than the corresponding + // template parameters in TD, causing unmatched constraint substitution. + // + // C++23 N4950 [temp.param]p12 + // A default template argument shall not be specified in a friend class + // template declaration. + while (ND->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None && + ND->getPreviousDecl()) + ND = ND->getPreviousDecl(); + return cast<TemplateDecl>(ND)->getTemplateParameters(); } DeclResult Sema::CheckClassTemplate( diff --git a/clang/test/SemaTemplate/concepts-friends.cpp b/clang/test/SemaTemplate/concepts-friends.cpp index 255b0858917fb6..31840309f1ec86 100644 --- a/clang/test/SemaTemplate/concepts-friends.cpp +++ b/clang/test/SemaTemplate/concepts-friends.cpp @@ -478,3 +478,27 @@ 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 N4950 [temp.param]p12. + 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); -}; +} >From 6acd29424d9a8c3febea004a68401439d5b7e5a0 Mon Sep 17 00:00:00 2001 From: Younan Zhang <zyn7...@gmail.com> Date: Fri, 29 Mar 2024 22:51:09 +0800 Subject: [PATCH 2/2] Expand comments --- clang/lib/Sema/SemaTemplate.cpp | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index 14fabe36eee794..4eca7d79897676 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -1836,19 +1836,27 @@ 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. - Decl *ND = TD->getMostRecentDecl(); - // Skip past friend Decls because they are not supposed to contain default - // template arguments. Moreover, these declarations may introduce template - // parameters living in different template depths than the corresponding - // template parameters in TD, causing unmatched constraint substitution. - // - // C++23 N4950 [temp.param]p12 + Decl *D = TD->getMostRecentDecl(); + // N3337 [temp.param]p12: // A default template argument shall not be specified in a friend class // template declaration. - while (ND->getFriendObjectKind() != Decl::FriendObjectKind::FOK_None && - ND->getPreviousDecl()) - ND = ND->getPreviousDecl(); - return cast<TemplateDecl>(ND)->getTemplateParameters(); + // + // Skip past friend *declarations* because they are not supposed to contain + // default template arguments. Moreover, these declarations may introduce + // template parameters living in different 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( _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
