in lib/generator.js [1805:1817]
visitCall(ast, level) {
// TODO 这块目前都进了method_call 下面两个分支不知道有没有用
assert.equal(ast.type, 'call');
if (ast.left.type === 'method_call') {
this.visitMethodCall(ast, level);
} else if (ast.left.type === 'instance_call') {
this.visitInstanceCall(ast, level);
} else if (ast.left.type === 'static_call') {
this.visitStaticCall(ast, level);
} else {
throw new Error('un-implemented');
}
}