Ranges don't always automatically work about wuffs HOT 5 CLOSED

This also seems to work:

var elem u8 = arr[in.a >> 6]

from wuffs.

I see now that I am supposed to be explicit about ranges when declaring vars:

var b u8[..0x3] = in.a >> 6
var elem u8 = arr[b]

If that's what I should be doing, then please do close this issue. Though I would argue that this should be in an FAQ somewhere; I assumed that Wuffs automatically did this.

from wuffs.

Yeah, that will work for now, but longer term, you probably shouldn't need the [..0x3] range refinement. Currently, after an assignment like x = y, we automatically add the fact x == y. In the future, we might also add facts x >= min_possible_y and x <= max_possible_y, although specifying exactly how to calculate the min and max values, especially if y is an expression, could be tricky. In your case, after b = in.a >> 6, that should implicitly assert that b <= 3, and so the array index arr[b] is proved in bounds, without needing the [..0x3].

But, yeah, in the very short term, adding [..0x3] will keep you moving.

from wuffs.

Awesome, thanks. Should this issue stay open then? I no longer have a blocking issue in the short term, but it would still be nice if this worked automatically.

from wuffs.

Let's keep the issue open for now.

from wuffs.