anchor.diff:    ///
     /// This is the most common kind of marking, and is used for most expressions
     /// and statements.
  -  SourceLocation _nodeStart(TreeNode node) => _getLocation(node.fileOffset);
  +  SourceLocation _nodeStart(TreeNode node) =>
  +      _toSourceLocation(node.fileOffset);
   
     /// Gets the end position of [node] for use in source mapping.
     ///
  
positive.code:       // _AsyncStarImpl has an example of the generated code.
        var gen = emitGeneratorFn((_) => [_asyncStarController]);
  
        var returnType = _getExpectedReturnType(function, _coreTypes.streamClass);
        var asyncStarImpl = InterfaceType(_asyncStarImplClass, [returnType]);
        return js.call('new #.new(#).stream', [_emitType(asyncStarImpl), gen]);
      }
  
negative.code:   }
  
    js_ast.PropertyAccess _emitJSInterop(NamedNode n) {
      var jsName = _jsNameWithoutGlobal(n);
      if (jsName == null) return null;
      return _emitJSInteropForGlobal(jsName);
    }
  