Have a lint against usize-to-u64 casts (or, against all integer casts) · Issue #9231 · rust-lang/rust-clippy (original) (raw)

What it does

I would like clippy to lint against all integer casts. So I have set:

#![warn( clippy::cast_possible_wrap, // unsigned -> signed clippy::cast_sign_loss, // signed -> unsigned clippy::cast_lossless, clippy::cast_possible_truncation, )]

However, I just by accident noticed that this does not lint against usize-to-u64 casts. I guess cast_possible_truncation says "this cannot truncate because we don't have more than 64bit pointer size", and "cast_lossless" says "ah this might be lossy on platforms with pointers larger than 64bit", and then neither of them does anything.

I would be happy to either have one of these lints also trigger on usize-to-u64 casts, or to have a new lint against all integer casts.

Lint Name

cast_integer

Category

pedantic

Advantage

Integer casts are subtle and should be done via From/TryFrom, never via as, so I want to rule out all of them in my codebase.

Drawbacks

No response

Example

pub fn foo(x: usize) -> u64 { x as u64 }

Could be written as:

pub fn foo(x: usize) -> u64 { u64::try_from(x).unwrap() }