error[E0759]: `v` has lifetime `'a` but it needs to satisfy a `'static` lifetime requirement
  --> $DIR/regions-close-object-into-object-4.rs:13:16
   |
LL | fn i<'a, T, U>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'static> {
   |                   ---------------- this data with lifetime `'a`...
LL |     Box::new(B(&*v)) as Box<dyn X>
   |                ^^^ ...is used and required to live as long as `'static` here
   |
note: `'static` lifetime requirement introduced by the return type
  --> $DIR/regions-close-object-into-object-4.rs:12:52
   |
LL | fn i<'a, T, U>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'static> {
   |                                                    ^^^^^^^ `'static` requirement introduced here
LL |     Box::new(B(&*v)) as Box<dyn X>
   |     ------------------------------ because of this returned expression
help: consider changing the trait object's explicit `'static` bound to the lifetime of argument `v`
   |
LL | fn i<'a, T, U>(v: Box<dyn A<U>+'a>) -> Box<dyn X + 'a> {
   |                                                    ~~
help: alternatively, add an explicit `'static` bound to this reference
   |
LL | fn i<'a, T, U>(v: Box<(dyn A<U> + 'static)>) -> Box<dyn X + 'static> {
   |                   ~~~~~~~~~~~~~~~~~~~~~~~~~

error: aborting due to previous error

For more information about this error, try `rustc --explain E0759`.