[clang] [libc] [llvm] [clang-tools-extra] [compiler-rt] [flang] [clang] Exclude non-template classes when checking if constraint refers to containing template arguments (PR #74265)

[via llvm-commits]

https://github.com/antangelo updated https://github.com/llvm/llvm-project/pull/74265

>From a8e841657b9816a78f6eb1520c8513454fe0008b Mon Sep 17 00:00:00 2001
From: Antonio Abbatangelo <contact at antangelo.com>
Date: Tue, 28 Nov 2023 21:19:13 -0500
Subject: [PATCH 1/2] [clang] Exclude non-template classes when checking if
 constraint refers to containing template arguments

---
 clang/docs/ReleaseNotes.rst         |  3 +++
 clang/lib/Sema/SemaTemplate.cpp     |  2 ++
 clang/test/SemaTemplate/GH71595.cpp | 34 +++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)
 create mode 100644 clang/test/SemaTemplate/GH71595.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c7a948fd3fae5..852b908dd1594 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -651,6 +651,9 @@ Bug Fixes in This Version
 - Fixed false positive error emitted by clang when performing qualified name
   lookup and the current class instantiation has dependent bases.
   Fixes (`#13826 <https://github.com/llvm/llvm-project/issues/13826>`_)
+- Fix a ``clang-17`` regression where a templated friend with constraints is not 
+  properly applied when its parameters reference an enclosing non-template class.
+  Fixes (`#71595 <https://github.com/llvm/llvm-project/issues/71595>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 09bbf14d39af5..aec802b289a2d 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -1714,6 +1714,8 @@ class ConstraintRefersToContainingTemplateChecker
   // Friend, likely because it was referred to without its template arguments.
   void CheckIfContainingRecord(const CXXRecordDecl *CheckingRD) {
     CheckingRD = CheckingRD->getMostRecentDecl();
+    if (!CheckingRD->isTemplated())
+      return;
 
     for (const DeclContext *DC = Friend->getLexicalDeclContext();
          DC && !DC->isFileContext(); DC = DC->getParent())
diff --git a/clang/test/SemaTemplate/GH71595.cpp b/clang/test/SemaTemplate/GH71595.cpp
new file mode 100644
index 0000000000000..7d34d1bf054e4
--- /dev/null
+++ b/clang/test/SemaTemplate/GH71595.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+
+template<class T, class U>
+concept C = true;
+
+class non_temp {
+    template<C<non_temp> T>
+    friend void f();
+
+    non_temp();
+};
+
+template<C<non_temp> T>
+void f() {
+    auto v = non_temp();
+}
+
+template<class A>
+class temp {
+    template<C<temp> T>
+    friend void g();
+
+    temp(); // expected-note {{implicitly declared private here}}
+};
+
+template<C<temp<int>> T>
+void g() {
+    auto v = temp<T>(); // expected-error {{calling a private constructor of class 'temp<int>'}}
+}
+
+void h() {
+    f<int>();
+    g<int>(); // expected-note {{in instantiation of function template specialization 'g<int>' requested here}}
+}

>From 7c27cd73781b64855b652ff18cd0fc3a0fb3dfac Mon Sep 17 00:00:00 2001
From: Antonio Abbatangelo <contact at antangelo.com>
Date: Sun, 3 Dec 2023 20:22:31 -0500
Subject: [PATCH 2/2] Fix trailing whitespace in release notes

---
 clang/docs/ReleaseNotes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 852b908dd1594..b7ebd17051be4 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -651,7 +651,7 @@ Bug Fixes in This Version
 - Fixed false positive error emitted by clang when performing qualified name
   lookup and the current class instantiation has dependent bases.
   Fixes (`#13826 <https://github.com/llvm/llvm-project/issues/13826>`_)
-- Fix a ``clang-17`` regression where a templated friend with constraints is not 
+- Fix a ``clang-17`` regression where a templated friend with constraints is not
   properly applied when its parameters reference an enclosing non-template class.
   Fixes (`#71595 <https://github.com/llvm/llvm-project/issues/71595>`_)