PR c++/90124 - bogus error with incomplete type in decltype.

	* typeck.c (build_class_member_access_expr): Check
	cp_unevaluated_operand.

	* g++.dg/cpp0x/decltype70.C: New test.

From-SVN: r270418

gcc/cp/ChangeLog

+2019-04-17  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/90124 - bogus error with incomplete type in decltype.
+	* typeck.c (build_class_member_access_expr): Check
+	cp_unevaluated_operand.
+
 2019-04-12  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/89933

gcc/cp/typeck.c

@@ -2477,7 +2477,8 @@ build_class_member_access_expr (cp_expr object, tree member,
 	  /* We didn't complain above about a currently open class, but now we
 	     must: we don't know how to refer to a base member before layout is
 	     complete.  But still don't complain in a template.  */
-	  if (!dependent_type_p (object_type)
+	  if (!cp_unevaluated_operand
+	      && !dependent_type_p (object_type)
 	      && !complete_type_or_maybe_complain (object_type, object,
 						   complain))
 	    return error_mark_node;

gcc/testsuite/ChangeLog

+2019-04-17  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/90124 - bogus error with incomplete type in decltype.
+	* g++.dg/cpp0x/decltype70.C: New test.
+
 2019-04-17  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/90095

gcc/testsuite/g++.dg/cpp0x/decltype70.C

+// PR c++/90124
+// { dg-do compile { target c++11 } }
+
+class a {
+public:
+  int b;
+};
+class c : a {
+  auto m_fn1() -> decltype(b);
+};