[CS1] fix #4260 and #1349: splat error with soak properties or expressions

[zdenko]

This is a fix for #4260 and #1349 when invalid JS is compiled if Splat contains soak accessor (?.), or if statement.

Before:

// [a if b...]
slice.call(  if (b) {
    a;
  });

// [a?.b...]
slice.call(  if (typeof a !== "undefined" && a !== null) {
    a.b;
  });

// arr.push(error.data?.errors...)
arr.push.apply(arr, if ((ref = error.data) != null) {
  ref.errors;
});

After:

// [a if b...]
slice.call((b ? a : void 0));

// [a?.b...]
slice.call((typeof a !== "undefined" && a !== null ? a.b : void 0));

// arr.push(error.data?.errors...)
arr.push.apply(arr, ((ref = error.data) != null ? ref.errors : void 0));

[GeoffreyBooth]

See #4644. I’m not sure this bug is severe enough that it’s worth fixing in 1.x. Since the current output throws runtime errors, this bug doesn’t cause any bugs in anyone’s code; it’s just that some syntax that should be allowable just isn’t, until #4644 gets merged in. Or to look at it another way, we add support for this syntax in CoffeeScript 2 😄

[zdenko]

@GeoffreyBooth void 0 is the problem. When the slice is called the correct output should be:

// [a?.b...]
slice.call((typeof a !== "undefined" && a !== null ? a.b : []));

I'll take a look.

[zdenko]

@GeoffreyBooth I think this should be fixed now.

[GeoffreyBooth]

Should this get LEVEL_OP too?

[connec]

In this case no, since in CS1 splats are not operators, but are instead handled by Arr and Assign.