rust/src/test/ui/suggestions/impl-trait-missing-lifetime.rs

// edition:2021

#![feature(anonymous_lifetime_in_impl_trait)]

// This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
fn f(_: impl Iterator<Item = &'_ ()>) {}

// But that lifetime does not participate in resolution.
fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
//~^ ERROR missing lifetime specifier

// This is understood as `fn foo<'_1>(_: impl Iterator<Item = &'_1 ()>) {}`.
async fn h(_: impl Iterator<Item = &'_ ()>) {}

// But that lifetime does not participate in resolution.
async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
//~^ ERROR missing lifetime specifier

fn main() {}