error[E0621]: explicit lifetime required in the type of `a` --> $DIR/issue-14285.rs:12:5 | LL | fn foo<'a>(a: &dyn Foo) -> B<'a> { | -------- help: add explicit lifetime `'a` to the type of `a`: `&'a (dyn Foo + 'a)` LL | B(a) | ^^^^ lifetime `'a` required error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0621`.