error[E0597]: borrowed value does not live long enough (Ast)
  --> $DIR/issue-46472.rs:4:10
   |
LL |     &mut 4
   |          ^ temporary value does not live long enough
...
LL | }
   | - temporary value only lives until here
   |
note: borrowed value must be valid for the lifetime 'a as defined on the function body at 3:8...
  --> $DIR/issue-46472.rs:3:8
   |
LL | fn bar<'a>() -> &'a mut u32 {
   |        ^^

error[E0515]: cannot return reference to temporary value (Mir)
  --> $DIR/issue-46472.rs:4:5
   |
LL |     &mut 4
   |     ^^^^^-
   |     |    |
   |     |    temporary value created here
   |     returns a reference to data owned by the current function

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0515, E0597.
For more information about an error, try `rustc --explain E0515`.