892583 - Understand why withStatement isn't syntax-parseable

Status: RESOLVED DUPLICATE of bug 1297706

(Core :: JavaScript Engine, defect)

Description

[Jason Orendorff [:jorendorff]]

A with-statement rules out syntax parsing for the entire compilation unit.

Brian, why is this?

If I remove the specialization that implements this, we get one test failure:
  test262/ch12/12.10/12.10-0-1.js
shown below. I'd like to understand why this fails. We use the same code to create the binding for 'foo' in both parse modes, so I don't see offhand why it's affected. But it is.


function testcase() {
  var o = {};
  var f = function () {
	/* capture foo binding before executing with */
	return foo;
      }

  with (o) {
    var foo = "12.10-0-1";
  }

  return f()==="12.10-0-1"

 }
runTestCase(testcase);

Comment 1

[Brian Hackett [Laid off!]]

I think that functions containing 'with' are not marked as having an extensible scope, even though they do, which will break TryConvertFreeName in the inner function.  I tried fixing the hasExtensibleScope thing and some mochitests broke or something and I didn't look into it.

Anyhow, I'd like to see this fixed too.  'with' is an ugly feature of the language but it's used by real web js and we shouldn't deoptimize parsing around it.