API parameters that are asserted to be non-zero should be of type NonZeroUsize or similar.

[khuey]

A number of parameters in various tokio APIs are usizes that must be non-zero, e.g. core_threads, max_threads, the argument to mpsc::channel, etc. The last one tripped me up when porting code because crossbeam::mpsc::channel(0) is equivalent to tokio::mpsc::channel(1). This can all be enforced in the type system and be caught at compile time.

[taiki-e]

Related: rust-lang/futures-rs#1803, smol-rs/async-channel#2

[khuey]

Seems that something like rust-lang/rust#69329 would be helpful here then.

[carllerche]

NonZeroUsize isn't really intended for APIs. It is intended to help the compiler optimize struct layout. It also is not idiomatic Rust.

[Lucretiel]

It also is not idiomatic Rust.

It's not? I've been more and more using it for this exact purpose, what's wrong with it?