anchor.diff:          params['column'] = col.toString();
         }
         Breakpoint bpt = await invokeRpc('addBreakpoint', params);
  -      if (bpt.resolved &&
  -          script.loaded &&
  -          script.tokenToLine(bpt.location.tokenPos) != line) {
  -        // TODO(turnidge): Can this still happen?
  -        script.getLine(line).possibleBpt = false;
  +      if (bpt.resolved && script.loaded) {
  +        SourceLocation loc = bpt.location;
  +        if (script.tokenToLine(loc.tokenPos) != line) {
  +          script.getLine(line).possibleBpt = false;
  +        }
         }
         return bpt;
       } on ServerRpcException catch(e) {
  
positive.code:   @observable int number;
  
    // Either SourceLocation or UnresolvedSourceLocation.
    @observable ServiceObject location;
  
    // The breakpoint is in a file which is not yet loaded.
    @observable bool latent;
  
negative.code:     if (bpt.location.tokenPos != null) {
        line = tokenToLine(bpt.location.tokenPos);
      } else {
        UnresolvedSourceLocation loc = bpt.location;
        line = loc.line;
      }
      getLine(line).addBreakpoint(bpt);
    }
  