[clang] fix getReplacedTemplateParameter for partial specialziations

clang/lib/AST/DeclTemplate.cpp

@@ -1670,20 +1670,25 @@ clang::getReplacedTemplateParameter(Decl *D, unsigned Index) {
     auto P = CTSD->getSpecializedTemplateOrPartial();
     TemplateParameterList *TPL;
     if (const auto *CTPSD =
-            dyn_cast<ClassTemplatePartialSpecializationDecl *>(P))
+            dyn_cast<ClassTemplatePartialSpecializationDecl *>(P)) {
       TPL = CTPSD->getTemplateParameters();
-    else
-      TPL = cast<ClassTemplateDecl *>(P)->getTemplateParameters();
+      // FIXME: Obtain Args deduced for the partial specialization.
+      return {TPL->getParam(Index), {}};
+    }
+    TPL = cast<ClassTemplateDecl *>(P)->getTemplateParameters();
     return {TPL->getParam(Index), CTSD->getTemplateArgs()[Index]};
   }
   case Decl::Kind::VarTemplateSpecialization: {
     const auto *VTSD = cast<VarTemplateSpecializationDecl>(D);
     auto P = VTSD->getSpecializedTemplateOrPartial();
     TemplateParameterList *TPL;
-    if (const auto *VTPSD = dyn_cast<VarTemplatePartialSpecializationDecl *>(P))
+    if (const auto *VTPSD =
+            dyn_cast<VarTemplatePartialSpecializationDecl *>(P)) {
       TPL = VTPSD->getTemplateParameters();
-    else
-      TPL = cast<VarTemplateDecl *>(P)->getTemplateParameters();
+      // FIXME: Obtain Args deduced for the partial specialization.
+      return {TPL->getParam(Index), {}};
+    }
+    TPL = cast<VarTemplateDecl *>(P)->getTemplateParameters();
     return {TPL->getParam(Index), VTSD->getTemplateArgs()[Index]};
   }
   case Decl::Kind::ClassTemplatePartialSpecialization:

clang/test/SemaTemplate/concepts.cpp

@@ -1476,3 +1476,20 @@ static_assert( requires {{ &f } -> C;} ); // expected-error {{reference to overl
 // expected-error@-1 {{static assertion failed due to requirement 'requires { { &f() } -> C; }'}}
 
 }
+
+namespace GH162770 {
+  enum e {};
+  template<e> struct s {};
+
+  template<typename> struct specialized;
+  template<e x> struct specialized<s<x>> {
+    static auto make(auto) -> s<x>;
+  };
+
+  template<e x> struct check {
+    static constexpr auto m = requires { specialized<s<x>>::make(0); };
+  };
+
+  template<typename... Ts> auto comma = (..., Ts());
+  auto b = comma<check<e{}>>;
+} // namespace GH162770

clang/test/SemaTemplate/partial-spec-instantiate.cpp

@@ -152,3 +152,16 @@ namespace GH60778 {
     ClassTemplate<>::Nested<int> instantiation;
   }
 }
+#if __cplusplus >= 201103L
+namespace GH162855 {
+  template <class...> using A = int;
+  template <class, int> struct B;
+  template <class...> struct C;
+  template <template <class, int...> class TT, long... X>
+  struct C<TT<int, X...>> {
+    template <class... Y> using l = A<B<Y, X>...>;
+  };
+  template <class> struct D;
+  template struct C<D<int>>;
+} // namespace GH162855
+#endif