`int` is not assignable to `int` (caused by inconsistent types when breaking cycles)

[connernilsen]

Type error assigning int to int in while loop. repro

Repro contents:

def decode(s: str):
    i = 0
    while i < len(s):
        j = i
        while (
            s[j] != ""
        ):
            j += 1
        i = j + 1

[AryanBagade]

@connernilsen Hey! I took a look at this issue and I think I found the rootcause.

With nested loops that have cyclic variable dependencies (j = i then i = j + 1), the type checker creates LoopRecursive type variables to handle the cycles. But when comparing types, it was rejecting these variables instead of using their underlying types, causing the false positive

[AryanBagade]

I tried to fix it !! Modified is_subset_eq in solver.rs ( to handle LoopRecursive variables appearing in the want position by using their prior type instead of throwing an internal error. and its working shall i create a pr??

[yangdanny97]

cc @stroxler for opinions on the approach

[AryanBagade]

any update on this ?

[stroxler]

I'm not 100% sure where the problem comes from (although there are two interlocking cycles here which I don't think is well-tested) so changing solver.rs to use prior types more aggressively is likely the solution.

So yes I think a PR would be helpful!

[AryanBagade]

@stroxler @yangdanny97 could you please review it, apologies for taking two weeks!