"multiple parameters named <value>" when destructuring params in args with duplicate default values

[hibachrach]

Bug report

Input Code

baz = ({ foo: _foo = false, bar: _bar = false } = {}) ->

Expected Behavior

var baz;

baz = function(arg) {
  var _bar, _foo, ref, ref1, ref2;
  ref = arg != null ? arg : {}, _foo = (ref1 = ref.foo) != null ? ref1 : false, _bar = (ref2 = ref.bar) != null ? ref2 : false;
};

Current Behavior

Error on line 1: multiple parameters named false

Context

This often comes up with constructor params where you have several named params which all default to false

Environment

This occurs with v1.12.7 but not whatever v2.x.x version is on the main (non-v2) website

• CoffeeScript version: v1.12.7
• Node.js version: v12.14.1

[ljluestc]

This appears to be a bug in that specific version of CoffeeScript. To resolve this issue, you can either upgrade to a newer version of CoffeeScript or modify your code to work around the problem.

Here's your code with a slight modification to avoid the issue:

baz = ({ foo: _foo, bar: _bar } = {}) ->
  _foo ?= false
  _bar ?= false

In this modified code, we use the ?= operator to assign a default value to _foo and _bar if they are undefined or null. This should work as expected and avoid the error you encountered in CoffeeScript v1.12.7.

[Inve1951]

fyi v1 website is still up: v1/#try