error[E0381]: used binding `x` isn't initialized
  --> $DIR/issue-78655.rs:3:5
   |
LL |     let x;
   |         - binding declared here but left uninitialized
LL |     &x
   |     ^^ `x` used here but it isn't initialized
   |
help: consider assigning a value
   |
LL |     let x = 42;
   |           ++++

error: could not evaluate constant pattern
  --> $DIR/issue-78655.rs:7:9
   |
LL |     let FOO = FOO;
   |         ^^^

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0381`.