c++: Member fns and deduction guide rewriting [PR98929]

My patch for 96199 had us re-substitute the parameter types of a constructor
in order to rewrite mentions of members into dependent references.  We need
to do that for member functions, too.

gcc/cp/ChangeLog:

	PR c++/98929
	PR c++/96199
	* error.c (dump_expr): Ignore dummy object.
	* pt.c (tsubst_baselink): Handle dependent scope.

gcc/testsuite/ChangeLog:

	PR c++/98929
	* g++.dg/cpp1z/class-deduction-decltype1.C: New test.

gcc/cp/error.c

@@ -2352,7 +2352,8 @@ dump_expr (cxx_pretty_printer *pp, tree t, int flags)
 	if (INDIRECT_REF_P (ob))
 	  {
 	    ob = TREE_OPERAND (ob, 0);
-	    if (!is_this_parameter (ob))
+	    if (!is_this_parameter (ob)
+		&& !is_dummy_object (ob))
 	      {
 		dump_expr (pp, ob, flags | TFF_EXPR_IN_PARENS);
 		if (TYPE_REF_P (TREE_TYPE (ob)))

gcc/cp/pt.c

@@ -16196,6 +16196,16 @@ tsubst_baselink (tree baselink, tree object_type,
       if (IDENTIFIER_CONV_OP_P (name))
 	name = make_conv_op_name (optype);
 
+      /* See maybe_dependent_member_ref.  */
+      if (dependent_scope_p (qualifying_scope))
+	{
+	  if (template_id_p)
+	    name = build2 (TEMPLATE_ID_EXPR, unknown_type_node, name,
+			   template_args);
+	  return build_qualified_name (NULL_TREE, qualifying_scope, name,
+				       /* ::template */false);
+	}
+
       if (name == complete_dtor_identifier)
 	/* Treat as-if non-dependent below.  */
 	dependent_p = false;

gcc/testsuite/g++.dg/cpp1z/class-deduction-decltype1.C

@@ -0,0 +1,11 @@
+// PR c++/98929
+// { dg-do compile { target c++17 } }
+
+template <typename T>
+struct A {
+  void foo ();
+  using c = decltype (foo ());
+  A (c);			// { dg-message {decltype \(A<T>::foo} }
+};
+A d;				// { dg-error "deduction failed" }
+// { dg-error "no match" "" { target *-*-* } .-1 }