anchor.diff:        if (scripts.isEmpty) {
           return [];
         }
  -      var script = scripts[0];
  +      var script = scripts.first;
         await script.load();
         if (!lineStrComplete) {
           // Complete the line.
  
positive.code: 
      if (scriptName != null) {
        // Resolve the script.
        var scripts = await _lookupScript(debugger.isolate, scriptName);
        if (scripts.length == 0) {
          return new DebuggerLocation.error("Script '${scriptName}' not found");
        } else if (scripts.length == 1) {
          return new DebuggerLocation.file(scripts[0], line, col);
        } else {
          // TODO(turnidge): Allow the user to disambiguate.
          return new DebuggerLocation.error(
  
negative.code:     var match = sourceLocMatcher.firstMatch(locDesc);
      if (match != null) {
        return _parseScriptLine(debugger, match);
      }
      match = packageLocMatcher.firstMatch(locDesc);
      if (match != null) {
        return _parseScriptLine(debugger, match, package: true);
      }
      match = functionMatcher.firstMatch(locDesc);
      if (match != null) {
  