error[E0277]: the trait bound `U: Copy` is not satisfied --> $DIR/wf-fn-where-clause.rs:8:24 | LL | fn foo() where T: ExtraCopy | ^^^^^^^^^^^^ the trait `Copy` is not implemented for `U` | note: required by a bound in `ExtraCopy` --> $DIR/wf-fn-where-clause.rs:6:19 | LL | trait ExtraCopy { } | ^^^^ required by this bound in `ExtraCopy` help: consider further restricting type parameter `U` | LL | fn foo() where T: ExtraCopy, U: std::marker::Copy | ++++++++++++++++++++++ error[E0038]: the trait `Copy` cannot be made into an object --> $DIR/wf-fn-where-clause.rs:12:16 | LL | fn bar() where Vec:, {} | ^^^^^^^^^^^^^ `Copy` cannot be made into an object | = note: the trait cannot be made into an object because it requires `Self: Sized` = note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit error[E0277]: the size for values of type `(dyn Copy + 'static)` cannot be known at compilation time --> $DIR/wf-fn-where-clause.rs:12:16 | LL | fn bar() where Vec:, {} | ^^^^^^^^^^^^^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `(dyn Copy + 'static)` note: required by a bound in `Vec` --> $DIR/wf-fn-where-clause.rs:16:12 | LL | struct Vec { | ^ required by this bound in `Vec` help: you could relax the implicit `Sized` bound on `T` if it were used through indirection like `&T` or `Box` --> $DIR/wf-fn-where-clause.rs:16:12 | LL | struct Vec { | ^ this could be changed to `T: ?Sized`... LL | t: T, | - ...if indirection were used here: `Box` error: aborting due to 3 previous errors Some errors have detailed explanations: E0038, E0277. For more information about an error, try `rustc --explain E0038`.