swiftParseParenFreeIfStatement.js

const plugin = (instance) => {
  instance.extend('parseParenFreeIfStatement', () => function parseParenFreeIfStatement(node) {
    this.next();
    node.test = this.parseExpression();
    node.consequent = this.parseBlock(false);
    node.alternate = this.eat(tt._else) ? this.parseParenFreeElseStatement() : null;
    return this.finishNode(node, 'IfStatement');
  });

  instance.extend('parseParenFreeElseStatement', () => function parseParenFreeElseStatement() {
    const node = this.startNode();

    return (this.match(tt._if))
      ? this.parseParenFreeIfStatement(node)
      : this.parseBlock(false);
  });

  instance.extend('parseIfStatement', inner => function parseIfStatement(node) {
    return (this.lookahead().type === tt.parenL)
      ? inner.call(this, node)
      : this.parseParenFreeIfStatement(node);
  });
};