The proposal is that by default the compiler would refuse to do an infallible conversion from `u32` to `usize`, but if you declare up front "this code assumes a

The proposal is that by default the compiler would refuse to do an infallible conversion from `u32` to `usize`, but if you declare up front "this code assumes at least a 32-bit target", then you gain the ability to do infallible conversions from u32 to usize. And if you declare up front "this code assumes at least a 64-bit target", you gain the ability to do infallible conversions from u64 to usize. Also, you can already convert u8 and u16 to usize infallibly, today. Only u32 and u64 currently require fallible conversions via try_from.