A lint to detect explicitly-annotated lifetimes which can be inferred

[bstrie]

I think a lint for code of the following form would be useful:

fn foo<'a>(x: &'a str) -> &'a str {
    x
}

This function signature contains explicit lifetimes which can be inferred by the compiler. I imagine that the lint would emit something like the following:

warning: unnecesary lifetime annotations
fn foo<'a>(x: &'a str) -> &'a str {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: signature can be written as follows:
fn foo(x: &str) -> &str {

Perhaps the suggested signature bit would be tricky. I also have no opinion regarding whether or not this lint would be on or off by default.

[steveklabnik]

/cc @Manishearth does clippy have something like this?

[Manishearth]

Yep! https://github.com/Manishearth/rust-clippy/wiki#needless_lifetimes

[steveklabnik]

Nice. Giving this a close, then.