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`.