error[E0621]: explicit lifetime required in the type of `a`
  --> $DIR/explicit-lifetime-required-14285.rs:14:5
   |
LL |     B(a)
   |     ^^^^ lifetime `'a` required
   |
help: add explicit lifetime `'a` to the type of `a`
   |
LL - fn foo<'a>(a: &dyn Foo) -> B<'a> {
LL + fn foo<'a>(a: &'a (dyn Foo + 'a)) -> B<'a> {
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0621`.