c++: Fix pretty printing the context of local class [PR99213]

My r10-7705 patch for PR94521 made us set TFF_NO_FUNCTION_ARGUMENTS when
pretty printing the function scope of a local class type in order to
eliminate infinite recursion with a function signature that contains
decltype([]{}).  But due to the way dump_function_decl works, this
change regressed our pretty printing of local class types whose context
contains a class template specialization, as in the testcase below, in
which we wrongly pretty print the two local types as 'A<T>::f<char>::S1'
and 'B<T>::f<int>::S2'.

This patch makes dump_scope pass TFF_NO_TEMPLATE_BINDINGS instead of
TFF_NO_FUNCTION_ARGUMENTS when pretty printing a function scope.  It
appears this is the strictly better flag to use: it avoids the infinite
recursion issue, it restores pretty printing of the function parameter
list, and it stops dump_function_decl from trying to print a function
template specialization in its own weird way.

Summary of pretty printing differences for the below testcase:

  r10-7704:   A<T>::f() [with U = char; T = int]::S1
              B<T>::f() [with T = int]::S2

  r10-7705:   A<T>::f<char>::S1
              B<T>::f<int>::S2

  this patch: A<int>::f<char>()::S1
              B<int>::f()::S2

gcc/cp/ChangeLog:

	PR c++/99213
	PR c++/94521
	* error.c (dump_scope): Pass TFF_NO_TEMPLATE_BINDINGS instead of
	TFF_NO_FUNCTION_ARGUMENTS when dumping a function scope.

gcc/testsuite/ChangeLog:

	PR c++/99213
	PR c++/94521
	* g++.dg/diagnostic/local1.C: New test.

gcc/cp/error.c

@@ -243,9 +243,7 @@ dump_scope (cxx_pretty_printer *pp, tree scope, int flags)
     }
   else if ((flags & TFF_SCOPE) && TREE_CODE (scope) == FUNCTION_DECL)
     {
-      if (DECL_USE_TEMPLATE (scope))
-	f |= TFF_NO_FUNCTION_ARGUMENTS;
-      dump_function_decl (pp, scope, f);
+      dump_function_decl (pp, scope, f | TFF_NO_TEMPLATE_BINDINGS);
       pp_cxx_colon_colon (pp);
     }
 }

gcc/testsuite/g++.dg/diagnostic/local1.C

@@ -0,0 +1,25 @@
+// PR c++/99213
+// { dg-do compile { target c++14 } }
+
+template <class T>
+struct A {
+  template <class U>
+  static auto f() {
+    struct S1{};
+    return S1{};
+  }
+};
+
+using type = void;
+using type = decltype(A<int>::f<char>()); // { dg-error "A<int>::f<char>\\(\\)::S1"  }
+
+template <class T>
+struct B {
+  static auto f() {
+    struct S2{};
+    return S2{};
+  }
+};
+
+using type = void;
+using type = decltype(B<int>::f()); // { dg-error "B<int>::f\\(\\)::S2"  }