1107712 - Make scoping for formals default initializer ES6-compliant

Status: RESOLVED DUPLICATE of bug 1022967

(Core :: JavaScript Engine, defect)

Description

[Shu-yu Guo [:shu]]

According to ES6, expressions in a function's formals get its own scope that is the parent of the locals scope. Consider:

function f(x = 42, y = function () { x++ }) {
  var x = 0;
  y();
  print(x); // supposed to print 0
}

See 9.2.13.26 [1]

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-functiondeclarationinstantiation

We totally don't do this right now.

Comment 1

[Morgan Phillips [:mrrrgn]]

In light of this irc conversation I'll bug Shu on IRC before starting work on this bug:  http://logs.glob.uno/?c=mozilla%23jsapi&s=26+Feb+2016&e=26+Feb+2016#c703620

Comment 2

[Shu-yu Guo [:shu]]

I was going to ask who opened this bug, and is it a dupe of bug 1022967. It turns out that I opened this bug, and yes.

Morgan, do you want to take a stab at this? I assigned myself to bug 1022967, but if you are interested in taking it I can advise.