error[E0271]: type mismatch resolving ` as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V` --> $DIR/issue-62203-hrtb-ice.rs:39:9 | LL | let v = Unit2.m( | - required by a bound introduced by this call LL | / L { LL | | LL | | LL | | f: |x| { ... | LL | | }, LL | | }, | |_________^ type mismatch resolving ` as T0<'r, (&u8,)>>::O == <_ as Ty<'r>>::V` | note: expected this to be `<_ as Ty<'_>>::V` --> $DIR/issue-62203-hrtb-ice.rs:21:14 | LL | type O = T::Output; | ^^^^^^^^^ = note: expected associated type `<_ as Ty<'_>>::V` found struct `Unit4` = help: consider constraining the associated type `<_ as Ty<'_>>::V` to `Unit4` or calling a method that returns `<_ as Ty<'_>>::V` = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html note: required by a bound in `T1::m` --> $DIR/issue-62203-hrtb-ice.rs:27:51 | LL | fn m<'a, B: Ty<'a>, F>(&self, f: F) -> Unit1 | - required by a bound in this associated function LL | where LL | F: for<'r> T0<'r, (>::V,), O = >::V>, | ^^^^^^^^^^^^^^^^^^^^ required by this bound in `T1::m` error[E0271]: expected `{closure@issue-62203-hrtb-ice.rs:42:16}` to be a closure that returns `Unit3`, but it returns `Unit4` --> $DIR/issue-62203-hrtb-ice.rs:39:9 | LL | let v = Unit2.m( | - required by a bound introduced by this call LL | / L { LL | | LL | | LL | | f: |x| { ... | LL | | }, LL | | }, | |_________^ expected `Unit3`, found `Unit4` | note: required for `L<{closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19}>` to implement `for<'r> T0<'r, (&'r u8,)>` --> $DIR/issue-62203-hrtb-ice.rs:17:16 | LL | impl<'a, A, T> T0<'a, A> for L | ^^^^^^^^^ ^^^^ LL | where LL | T: FnMut(A) -> Unit3, | ----- unsatisfied trait bound introduced here note: required by a bound in `T1::m` --> $DIR/issue-62203-hrtb-ice.rs:27:12 | LL | fn m<'a, B: Ty<'a>, F>(&self, f: F) -> Unit1 | - required by a bound in this associated function LL | where LL | F: for<'r> T0<'r, (>::V,), O = >::V>, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `T1::m` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0271`.