Issue with referencing this in async method default arguments

[jimmydief]

Thanks for all of the work on this awesome plugin! I came across an instance where the plugin, when combined with @babel/preset-env, generates some invalid code.

Original code:

class A {
	async a(x = this.x())  {}
}

The issue is that the line that applies the default arg references _this but appears outside of the scope where _this is defined.

Generated code:

"use strict";

function _instanceof(left, right) { if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) { return right[Symbol.hasInstance](left); } else { return left instanceof right; } }

function _classCallCheck(instance, Constructor) { if (!_instanceof(instance, Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }

var A =
/*#__PURE__*/
function () {
  function A() {
    _classCallCheck(this, A);
  }

  _createClass(A, [{
    key: "a",
    value: function () {
      var x = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : _this.x();
      return function () {
        var _this = this;
      }.apply(this);
    }
  }]);

  return A;
}();

Heres' my Babel config:

{
	presets: ['env'],
	plugins: ['transform-async-to-promises']
}

Here it is on the Babel REPL.

And some version info:
node: 8.11.1
@babel/core: 7.3.3
@babel/preset-env: 7.3.1
babel-plugin-transform-async-to-promises: 0.8.5

[rpetrich]

@jimmydief Thanks for sending this test case. It exposed the lack of proper support for default arguments. This should be remedied in 0.8.10

[jimmydief]

Thanks again for the quick fix!