Nodes: Infinite loop possible when for loop uses a variable as its step value

[dstepanov]

When using for with a range and a step value CS is determining the iteration condition by its sign in a case when value is available, otherwise it will compare min and max values of the range definition.

I don't think it is the correct behaviour I would expect it to use the step value to determine its condition.

Example:

for i in [@min..@max] by 1
  alert i

var i, _ref, _ref2;
for (i = _ref = this.min, _ref2 = this.max; i <= _ref2; i += 1) {
  alert(i);
}

Negative step value with change the condition:

for i in [@min..@max] by -1
  alert i

var i, _ref, _ref2;
for (i = _ref = this.min, _ref2 = this.max; i >= _ref2; i += -1) {
  alert(i);
}

Unknown step value will not effect the condition of the loop in runtime:

for i in [@min..@max] by @steps
  alert i

var i, _ref, _ref2, _ref3;
for (i = _ref = this.min, _ref2 = this.max, _ref3 = this.steps; _ref <= _ref2 ? i <= _ref2 : i >= _ref2; i += _ref3) {
  alert(i);
}

In my case I can't see an additional if to be useful, when min > max and a step value is positive it will cause an infinite loop.

[tokland]

I was just bitten by this (v1.3.3):

coffee> step = 1
coffee> xs = (x for x in [3..1] by step)
FATAL ERROR: JS Allocation failed - process out of memory