warning: to use a constant of type `CustomEq` in a pattern, the constant's initializer must be trivial or `CustomEq` must be annotated with `#[derive(PartialEq, Eq)]`
  --> $DIR/custom-eq-branch-warn.rs:29:9
   |
LL |         BAR_BAZ => panic!(),
   |         ^^^^^^^
   |
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #73448 <https://github.com/rust-lang/rust/issues/73448>
   = note: the traits must be derived, manual `impl`s are not sufficient
   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
   = note: `#[warn(nontrivial_structural_match)]` on by default

warning: 1 warning emitted