如何获得MethodInvocation的完全限定目标？

我试图找到一种特定方法的用法.在这种情况下,我想找到的用法/调用foo.go(),但不是bar.go().下面的代码将找到go()任何类的所有调用.在下面的代码中,node.target简单地给出了我x的var名称,但我正在努力弄清楚方法属于哪个类.

test.dart

void main() {
  var x = new Foo();
  x.go();

  x = new Bar();
  x.go();
}

class Foo {
  go() {
    print('I am foo');
  }
}

class Bar {
  go() {
    print('I am bar');
  }
}

analyze.dart

import 'package:analyzer/analyzer.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/visitor.dart';

void main() {
  var targetFile = parseDartFile('test.dart');
  var visitor    = new UsageVisitor('foo.go');
  targetFile.visitChildren(visitor);
}

class UsageVisitor extends UnifyingAstVisitor {
  String _class;
  String _method;

  UsageVisitor(this._class, this._method);

  @override
  visitMethodInvocation(MethodInvocation node) {
    print({
      'target'    : node.target.toString(),    // in both cases, gives "x" -- I need "Foo" and "Bar", respectively
      'methodName': node.methodName.toString() // gives "go"
    });

    return super.visitNode(node);
  }
}

我如何区分(在分析仪级别),foo.go()和之间bar.go()？