error[E0308]: mismatched types --> $DIR/rfc1623-2.rs:28:8 | LL | f: &id, | ^^^ one type is more general than the other | = note: expected trait `for<'a, 'b> Fn<(&'a Foo<'b>,)>` found trait `Fn<(&Foo<'_>,)>` error[E0308]: mismatched types --> $DIR/rfc1623-2.rs:28:8 | LL | f: &id, | ^^^ one type is more general than the other | = note: expected trait `for<'a, 'b> Fn<(&'a Foo<'b>,)>` found trait `Fn<(&Foo<'_>,)>` error: implementation of `FnOnce` is not general enough --> $DIR/rfc1623-2.rs:28:8 | LL | f: &id, | ^^^ implementation of `FnOnce` is not general enough | = note: `fn(&'2 Foo<'_>) -> &'2 Foo<'_> {id::<&'2 Foo<'_>>}` must implement `FnOnce<(&'1 Foo<'b>,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&'2 Foo<'_>,)>`, for some specific lifetime `'2` error: implementation of `FnOnce` is not general enough --> $DIR/rfc1623-2.rs:28:8 | LL | f: &id, | ^^^ implementation of `FnOnce` is not general enough | = note: `fn(&Foo<'2>) -> &Foo<'2> {id::<&Foo<'2>>}` must implement `FnOnce<(&'a Foo<'1>,)>`, for any lifetime `'1`... = note: ...but it actually implements `FnOnce<(&Foo<'2>,)>`, for some specific lifetime `'2` error: aborting due to 4 previous errors For more information about this error, try `rustc --explain E0308`.