error[E0308]: mismatched types
  --> $DIR/const.rs:26:9
   |
LL |         FOO => {}, //~ ERROR mismatched types
   |         ^^^ expected &Foo, found struct `Foo`
   |
   = note: expected type `&Foo`
              found type `Foo`

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0308"