Currently, the lifetime elision doc only documents function definitions, but lifetime elision is also allowed in the following other locations:
fn types, such as fn(&T)
Fn/FnMut/FnOnce, such as Fn(&T)
impl headers
To demo this up, I made some type aliases for fn/Fn which you can pass &T as a parameter to (to follow the lifetime rules of the surrounding context), and compared what you get with that instead of using fn/Fn directly, where lifetime elision takes on the rules from fn/Fn/etc.
The demo was half for this change description, and half just to make sure I understand Rust -- in particular, I really had to reverse engineer it for impl because I wasn't sure, and it didn't seem to be documented anywhere (at least not here!)
Currently, the lifetime elision doc only documents function definitions, but lifetime elision is also allowed in the following other locations:
fntypes, such asfn(&T)Fn/FnMut/FnOnce, such asFn(&T)implheadersTo demo this up, I made some type aliases for
fn/Fnwhich you can pass&Tas a parameter to (to follow the lifetime rules of the surrounding context), and compared what you get with that instead of usingfn/Fndirectly, where lifetime elision takes on the rules fromfn/Fn/etc.I also demoed up an
implheader that used lifetime elision twice, although the error message in that case is broken (filed https://github.com/rust-lang/rust/issues/87763)The demo was half for this change description, and half just to make sure I understand Rust -- in particular, I really had to reverse engineer it for
implbecause I wasn't sure, and it didn't seem to be documented anywhere (at least not here!)https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=f82b280de4b992f225bc32121f333e96