[clang] [Clang][Concepts] Fix the constraint equivalence checking for TemplateTypeParmTypes (PR #102131)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/102131

>From aa99ac433c9d383bfca732c19e5082a555f64c2d Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Tue, 6 Aug 2024 20:08:43 +0800
Subject: [PATCH] [Clang][Concepts] Fix the constraint equivalence checking for
 TemplateTypeParmTypes

---
 clang/lib/Sema/SemaConcept.cpp                | 11 +++++++--
 .../SemaTemplate/concepts-out-of-line-def.cpp | 23 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index d4c9d044985e34..14a67f35a8f9f8 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -972,8 +972,15 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
   // equivalence.
   LocalInstantiationScope ScopeForParameters(S);
   if (auto *FD = DeclInfo.getDecl()->getAsFunction())
-    for (auto *PVD : FD->parameters())
-      ScopeForParameters.InstantiatedLocal(PVD, PVD);
+    for (auto *PVD : FD->parameters()) {
+      if (!PVD->isParameterPack()) {
+        ScopeForParameters.InstantiatedLocal(PVD, PVD);
+        continue;
+      }
+      // Parameter packs should expand to a size-of-1 argument.
+      ScopeForParameters.MakeInstantiatedLocalArgPack(PVD);
+      ScopeForParameters.InstantiatedLocalPackArg(PVD, PVD);
+    }
 
   std::optional<Sema::CXXThisScopeRAII> ThisScope;
 
diff --git a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
index 0142efcdc3ee86..333187b0d74ad6 100644
--- a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
+++ b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
@@ -599,3 +599,26 @@ template <class DerT>
 unsigned long DerivedCollection<DerTs...>::index() {}
 
 } // namespace GH72557
+
+namespace GH101735 {
+
+template <class, class>
+concept True = true;
+
+template <typename T>
+class A {
+  template <typename... Ts>
+  void method(Ts&... ts)
+    requires requires (T t) {
+      { t.method(static_cast<Ts &&>(ts)...) } -> True<void>;
+    };
+};
+
+template <typename T>
+template <typename... Ts>
+void A<T>::method(Ts&... ts)
+  requires requires (T t) {
+    { t.method(static_cast<Ts &&>(ts)...) } -> True<void>;
+  } {}
+
+}