Use failedAt in more places

pkg/compiler/lib/src/io/position_information.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Source information system mapping that attempts a semantic mapping between
 /// offsets of JavaScript code points to offsets of Dart code points.
 
 library dart2js.source_information.position;
 
 import '../common.dart';
@@ skipping 635 matching lines @@
       // function(){}()  new Function("...")()
       //             ^                      ^
       return new CallPosition(
           node.target, CodePositionKind.END, SourcePositionKind.INNER);
     } else if (node.target is js.Binary || node.target is js.Call) {
       // (0,a)()   m()()
       //      ^       ^
       return new CallPosition(
           node.target, CodePositionKind.END, SourcePositionKind.INNER);
     } else {
-      assert(invariant(NO_LOCATION_SPANNABLE, false,
-          message: "Unexpected property access ${nodeToString(node)}:\n"
+      assert(

[Johnni Winther, 2017/05/24 08:24:52]

Add a TODO for me to maybe remove this assertion.

[sra1, 2017/05/24 17:38:54]

Done.

+          false,
+          failedAt(
+              NO_LOCATION_SPANNABLE,
+              "Unexpected property access ${nodeToString(node)}:\n"
               "${DebugPrinter.prettyPrint(node)}"));
       // Don't know....
       return new CallPosition(
           node, CodePositionKind.START, SourcePositionKind.START);
     }
   }
 }
 
 class Offset {
   /// The offset of the enclosing statement relative to the beginning of the
@@ skipping 668 matching lines @@
 
   @override
   CodePosition operator [](js.Node node) {
     CodePosition codePosition = codePositions[node];
     if (codePosition == null) {
       coverage.registerNodesWithoutOffset(node);
     }
     return codePosition;
   }
 }