Function parenExpr

static/libs/javascript.js:427–430

(type)

    return expressionInner(type, value, true);
  }
  function parenExpr(type) {
    if (type != "(") return pass()
    return cont(pushlex(")"), maybeexpression, expect(")"), poplex)
  }
  function expressionInner(type, value, noComma) {
    if (cx.state.fatArrowAt == cx.stream.start) {
      var body = noComma ? arrowBodyNoComma : arrowBody;