error[E0597]: borrowed value does not live long enough
  --> $DIR/regions-creating-enums.rs:23:17
   |
LL |         return &Ast::Num((*f)(x)); //~ ERROR borrowed value does not live long enough
   |                 ^^^^^^^^^^^^^^^^^- temporary value only lives until here
   |                 |
   |                 temporary value does not live long enough
   |
note: borrowed value must be valid for the lifetime 'a as defined on the function body at 20:13...
  --> $DIR/regions-creating-enums.rs:20:13
   |
LL | fn map_nums<'a,'b, F>(x: &Ast, f: &mut F) -> &'a Ast<'b> where F: FnMut(usize) -> usize {
   |             ^^
   = note: consider using a `let` binding to increase its lifetime

error[E0597]: borrowed value does not live long enough
  --> $DIR/regions-creating-enums.rs:28:17
   |
LL |         return &Ast::Add(m_x, m_y);  //~ ERROR borrowed value does not live long enough
   |                 ^^^^^^^^^^^^^^^^^^- temporary value only lives until here
   |                 |
   |                 temporary value does not live long enough
   |
note: borrowed value must be valid for the lifetime 'a as defined on the function body at 20:13...
  --> $DIR/regions-creating-enums.rs:20:13
   |
LL | fn map_nums<'a,'b, F>(x: &Ast, f: &mut F) -> &'a Ast<'b> where F: FnMut(usize) -> usize {
   |             ^^
   = note: consider using a `let` binding to increase its lifetime

error: aborting due to 2 previous errors

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