error[E0106]: missing lifetime specifier
  --> $DIR/impl-trait-missing-lifetime-gated.rs:8:50
   |
LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
   |                                                  ^^ expected named lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime
   |
LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
   |                                                  ~~~~~~~

error[E0106]: missing lifetime specifier
  --> $DIR/impl-trait-missing-lifetime-gated.rs:18:56
   |
LL | async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
   |                                                        ^^ expected named lifetime parameter
   |
   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime
   |
LL | async fn i(x: impl Iterator<Item = &'_ ()>) -> Option<&'static ()> { x.next() }
   |                                                        ~~~~~~~

error[E0658]: anonymous lifetimes in `impl Trait` are unstable
  --> $DIR/impl-trait-missing-lifetime-gated.rs:5:31
   |
LL | fn f(_: impl Iterator<Item = &'_ ()>) {}
   |                               ^^
   |
   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable

error[E0658]: anonymous lifetimes in `impl Trait` are unstable
  --> $DIR/impl-trait-missing-lifetime-gated.rs:8:31
   |
LL | fn g(x: impl Iterator<Item = &'_ ()>) -> Option<&'_ ()> { x.next() }
   |                               ^^
   |
   = help: add `#![feature(anonymous_lifetime_in_impl_trait)]` to the crate attributes to enable

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0106, E0658.
For more information about an error, try `rustc --explain E0106`.