error[E0404]: expected trait, found derive macro `Hash` --> $DIR/issue-37534.rs:1:16 | LL | struct Foo { } | ^^^^ not a trait | help: consider importing this trait instead | LL + use std::hash::Hash; | warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported --> $DIR/issue-37534.rs:1:12 | LL | struct Foo { } | ^ error[E0392]: parameter `T` is never used --> $DIR/issue-37534.rs:1:12 | LL | struct Foo { } | ^ unused parameter | = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData` error: aborting due to 2 previous errors; 1 warning emitted Some errors have detailed explanations: E0392, E0404. For more information about an error, try `rustc --explain E0392`.