error[E0277]: the trait bound `U: Copy` is not satisfied --> $DIR/wf-trait-bound.rs:10:14 | LL | where T: ExtraCopy | ^^^^^^^^^^^^ the trait `Copy` is not implemented for `U` | note: required by a bound in `ExtraCopy` --> $DIR/wf-trait-bound.rs:7:19 | LL | trait ExtraCopy { } | ^^^^ required by this bound in `ExtraCopy` help: consider further restricting type parameter `U` | LL | where T: ExtraCopy, U: std::marker::Copy | ++++++++++++++++++++++ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.