ICE when casting negative discriminant enum values to anything less than bit width

[afinch7]

Compiling this code on playground:

enum Nums {
    NegOne = -1,
}

fn main() {
    let kind = Nums::NegOne;
    let _v = kind as i32;
}

results in ICE. Casting to anything smaller than usize/isize(u32, u16, i16, u8, i8, etc) also results in ICE. Casting to anything same size or larger(u128, i128, u64, i64, etc) works fine. Positive discriminant values also work fine.
Version of rustc: rustc 1.42.0 (b8cedc004 2020-03-09) running on x86_64-unknown-linux-gnu(on rust playground)
Compiler flags listed as used: -C codegen-units=1 -C debuginfo=2 --crate-type bin

[pnkfelix]

godbolt indicates that this was injected in Rust 1.40

[RalfJung]

Thanks for the report!

Please always include the ICE message. This time, it seems to be

Unsigned value 0xffffffffffffffff does not fit in 32 bits