error[E0046]: not all trait items implemented, missing: `req`
  --> $DIR/impl-with-default-fn-fail.rs:12:1
   |
LL |     fn req(&self);
   |     -------------- `req` from trait
...
LL | impl const Tr for u16 {
   | ^^^^^^^^^^^^^^^^^^^^^ missing `req` in implementation

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0046`.