bad comparison of upcasted values

[llogiq]

E.g. let x : u8 = ...; x as u32 > 300 maybe check sign of casted previously unsigned values.

[creativcoder]

I would like to work on this. Can you please elaborate more about this issue ?

[Manishearth]

So here we need to check for situations where we are casting before comparing, i.e. x as u32 > 200 or x as u32 < 0, and the original type has a range such that the comparison will always be true or always be false.

...actually, this isn't really an easy bug since you have to look up the value of x and ensure its not getting written to.

[Manishearth]

#97 should be easier. Its a simple check_ty with most of the details explained in the last comment. There are some complications there but I'll explain how to handle them when we reach that stage.

[llogiq]

I don't think so. It should suffice matching a comparison where one of the operands is an ExprCast whose inner expression has a primitive type that is smaller than the comapred value (via expr_ty)

[Manishearth]

Ah, I misunderstood the issue. In that case this isn't too hard.