diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -370,8 +370,8 @@
 
   case Template:
   case TemplateExpansion:
-    return TemplateArg.Name == Other.TemplateArg.Name &&
-           TemplateArg.NumExpansions == Other.TemplateArg.NumExpansions;
+    return getAsTemplateOrTemplatePattern().getAsTemplateDecl() ==
+           Other.getAsTemplateOrTemplatePattern().getAsTemplateDecl();
 
   case Declaration:
     return getAsDecl() == Other.getAsDecl();
diff --git a/clang/test/CXX/dcl/dcl.fct/p17.cpp b/clang/test/CXX/dcl/dcl.fct/p17.cpp
--- a/clang/test/CXX/dcl/dcl.fct/p17.cpp
+++ b/clang/test/CXX/dcl/dcl.fct/p17.cpp
@@ -257,4 +257,21 @@
   static_assert(is_same_v<decltype(S2(1)), S2>);
   // expected-error@-1{{no matching}}
   static_assert(is_same_v<decltype(S2('a')), S2>);
+
+  template <typename T>
+  struct S3 {};
+  // expected-note@-1 {{'S3' declared here}}
+  // expected-note@-2 {{template is declared here}}
+  void f23(C2<::S3> auto);
+  // expected-error@-1 {{no template named 'S3' in the global namespace; did you mean simply 'S3'?}}
+  // expected-error@-2 {{use of class template '::S3' requires template arguments}}
+}
+
+template <typename T>
+struct S4 {};
+// expected-note@-1 {{template is declared here}}
+
+namespace constrained {
+  void f24(C2<::S4> auto);
+  // expected-error@-1 {{use of class template '::S4' requires template arguments}}
 }