error[E0015]: cannot match on `str` in constant functions
  --> $DIR/match-non-const-eq.rs:7:9
   |
LL |         "a" => (), //FIXME [gated]~ ERROR can't compare `str` with `str` in const contexts
   |         ^^^
   |
   = note: `str` cannot be compared in compile-time, and therefore cannot be used in `match`es
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

error: aborting due to previous error

For more information about this error, try `rustc --explain E0015`.