error[E0597]: `*b` does not live long enough
  --> $DIR/issue-12470.rs:28:19
   |
LL |     let bb: &B = &*b;    //~ ERROR does not live long enough
   |                   ^^ borrowed value does not live long enough
LL |     make_a(bb)
LL | }
   | - borrowed value only lives until here
   |
note: borrowed value must be valid for the lifetime 'a as defined on the function body at 26:16...
  --> $DIR/issue-12470.rs:26:16
   |
LL | fn make_make_a<'a>() -> A<'a> {
   |                ^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0597`.