[clang] [Clang][Sema] Fix a bug on type constraint checking (PR #84671)

[Qizhi Hu via cfe-commits]

https://github.com/jcsxky created https://github.com/llvm/llvm-project/pull/84671

Try to fix https://github.com/llvm/llvm-project/issues/84368
[temp.friend]p1:
Similarly, each specialization of the `task` class template has the class template
specialization `task<int>` as a friend, and has all specializations of the class template `frd` as friends.

>From 9abe798955b0db77e12f0aec43cd23926a2b4744 Mon Sep 17 00:00:00 2001
From: huqizhi <huqizhi at feysh.com>
Date: Sun, 10 Mar 2024 16:11:18 +0800
Subject: [PATCH] [Clang][Sema] Fix a bug on type constraint checking

---
 clang/docs/ReleaseNotes.rst                    |  2 ++
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp |  1 +
 clang/test/Sema/PR84368.cpp                    | 16 ++++++++++++++++
 3 files changed, 19 insertions(+)
 create mode 100644 clang/test/Sema/PR84368.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3b89d5a8720785..b32e739288dbc5 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -259,6 +259,8 @@ Bug Fixes in This Version
   operator.
   Fixes (#GH83267).
 
+- Fix a bug on type constraint checking (#GH84368). 
+
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 20c2c93ac9c7b4..765c5bc689ae1e 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1698,6 +1698,7 @@ Decl *TemplateDeclInstantiator::VisitClassTemplateDecl(ClassTemplateDecl *D) {
     assert(!Owner->isDependentContext());
     Inst->setLexicalDeclContext(Owner);
     RecordInst->setLexicalDeclContext(Owner);
+    Inst->setObjectOfFriendDecl();
 
     if (PrevClassTemplate) {
       Inst->setCommonPtr(PrevClassTemplate->getCommonPtr());
diff --git a/clang/test/Sema/PR84368.cpp b/clang/test/Sema/PR84368.cpp
new file mode 100644
index 00000000000000..073530ffd8abea
--- /dev/null
+++ b/clang/test/Sema/PR84368.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+// RUN: %clang_cc1 -std=c++23 -verify %s
+// expected-no-diagnostics
+
+template<class T> concept IsOk = requires() { typename T::Float; };
+
+template<IsOk T> struct Thing;
+
+template<IsOk T> struct Foobar {
+	template<int> struct Inner {
+		template<IsOk T2> friend struct Thing;
+	};
+};
+
+struct MyType { using Float=float; };
+Foobar<MyType>::Inner<0> foobar;