PR c++/89831 - error with qualified-id in const member function.

Since the fix for 15272 we were remembering the wrong function to use at
instantiation time, because the type of the SCOPE_REF didn't reflect the
cv-quals of 'this'.  Conveniently, we can fix this by simplifying the code.

	* semantics.c (finish_non_static_data_member): Use object cv-quals
	in scoped case, too.

From-SVN: r269977

gcc/cp/ChangeLog

 2019-03-27  Jason Merrill  <jason@redhat.com>
 
+	PR c++/89831 - error with qualified-id in const member function.
+	* semantics.c (finish_non_static_data_member): Use object cv-quals
+	in scoped case, too.
+
 	PR c++/89421 - ICE with lambda in template parameter list.
 	* parser.c (cp_parser_lambda_expression): Also reject a lambda in a
 	template parameter list before C++20.

gcc/cp/semantics.c

@@ -1861,7 +1861,7 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
 
   if (current_class_ptr)
     TREE_USED (current_class_ptr) = 1;
-  if (processing_template_decl && !qualifying_scope)
+  if (processing_template_decl)
     {
       tree type = TREE_TYPE (decl);
 
@@ -1882,17 +1882,16 @@ finish_non_static_data_member (tree decl, tree object, tree qualifying_scope)
 	  type = cp_build_qualified_type (type, quals);
 	}
 
-      ret = (convert_from_reference
-	      (build_min (COMPONENT_REF, type, object, decl, NULL_TREE)));
+      if (qualifying_scope)
+	/* Wrap this in a SCOPE_REF for now.  */
+	ret = build_qualified_name (type, qualifying_scope, decl,
+				    /*template_p=*/false);
+      else
+	ret = (convert_from_reference
+	       (build_min (COMPONENT_REF, type, object, decl, NULL_TREE)));
     }
   /* If PROCESSING_TEMPLATE_DECL is nonzero here, then
-     QUALIFYING_SCOPE is also non-null.  Wrap this in a SCOPE_REF
-     for now.  */
-  else if (processing_template_decl)
-    ret = build_qualified_name (TREE_TYPE (decl),
-				qualifying_scope,
-				decl,
-				/*template_p=*/false);
+     QUALIFYING_SCOPE is also non-null.  */
   else
     {
       tree access_type = TREE_TYPE (object);

gcc/testsuite/g++.dg/template/scope6.C

+// PR c++/89831
+
+struct Q { 
+    int operator[](int i) { return 0; }
+    int operator[](int i) const { return 0; }
+};
+
+struct Base {
+    Q x;
+};
+struct X : public Base {
+    template <typename T>
+    void f(T) const {
+        int q = Base::x[0];
+    }   
+};
+int main() { X().f(3); }