[Concepts] Fix bug when referencing function parameters in instantiated function template requires clause

Fixes bug llvm#44613 - incorrect instantiated parameters were being added when checking instantiated function constraints

Author: saarraz

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -4252,9 +4252,9 @@ bool Sema::CheckInstantiatedFunctionTemplateConstraints(
         MLTAL.getInnermost(), SourceRange());
     if (Inst.isInvalid())
       return true;
-    if (addInstantiatedParametersToScope(*this, Decl,
-                                        Decl->getTemplateInstantiationPattern(),
-                                         Scope, MLTAL))
+    if (addInstantiatedParametersToScope(
+            *this, Decl, Decl->getPrimaryTemplate()->getTemplatedDecl(),
+            Scope, MLTAL))
       return true;
   }
 

clang/test/SemaTemplate/instantiate-requires-clause.cpp

@@ -29,3 +29,13 @@ using f31 = decltype(f3('a'));
 using f32 = decltype(f3(1, 'b'));
 using f33 = decltype(f3(1, 'b', 2));
 // expected-error@-1 {{no matching function for call to 'f3'}}
+
+template<typename T>
+struct S {
+	template<typename U>
+	static constexpr auto f(U const index) requires(index, true) {
+		return true;
+	}
+};
+
+static_assert(S<void>::f(1));