From 9c24fca2a33fc0fd059e278bb95c84803dfff9ae Mon Sep 17 00:00:00 2001
From: Saar Raz <saar@raz.email>
Date: Mon, 27 Jan 2020 00:57:31 +0200
Subject: [PATCH] [Concepts] Fix incorrect TemplateArgs for introduction of
 local parameters

The wrong set of TemplateArgs was being provided to addInstantiatedParametersToScope.
Caused bug #44658.
---
 clang/lib/Sema/SemaTemplateInstantiateDecl.cpp          | 7 +++----
 clang/test/SemaTemplate/instantiate-requires-clause.cpp | 7 +++++++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index fbbab8f..2e437cb 100755
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4246,18 +4246,17 @@ bool Sema::CheckInstantiatedFunctionTemplateConstraints(
   Sema::ContextRAII savedContext(*this, Decl);
   LocalInstantiationScope Scope(*this);
 
-  MultiLevelTemplateArgumentList MLTAL =
-    getTemplateInstantiationArgs(Decl, nullptr, /*RelativeToPrimary*/true);
-
   // If this is not an explicit specialization - we need to get the instantiated
   // version of the template arguments and add them to scope for the
   // substitution.
   if (Decl->isTemplateInstantiation()) {
     InstantiatingTemplate Inst(*this, Decl->getPointOfInstantiation(),
         InstantiatingTemplate::ConstraintsCheck{}, Decl->getPrimaryTemplate(),
-        MLTAL.getInnermost(), SourceRange());
+        TemplateArgs, SourceRange());
     if (Inst.isInvalid())
       return true;
+    MultiLevelTemplateArgumentList MLTAL(
+        *Decl->getTemplateSpecializationArgs());
     if (addInstantiatedParametersToScope(
             *this, Decl, Decl->getPrimaryTemplate()->getTemplatedDecl(),
             Scope, MLTAL))
diff --git a/clang/test/SemaTemplate/instantiate-requires-clause.cpp b/clang/test/SemaTemplate/instantiate-requires-clause.cpp
index 31cf484..8e9d5bf 100644
--- a/clang/test/SemaTemplate/instantiate-requires-clause.cpp
+++ b/clang/test/SemaTemplate/instantiate-requires-clause.cpp
@@ -51,3 +51,10 @@ struct S2 {
 
 static_assert((S2<int>::f(), true));
 
+template<typename T>
+struct S3 {
+	template<typename... Args> requires true
+	static constexpr void f(Args...) { }
+};
+
+static_assert((S3<int>::f(), true));
\ No newline at end of file
-- 
2.7.4