error[E0277]: the trait bound `T: Copy` is not satisfied
  --> $DIR/wf-in-fn-ret.rs:10:16
   |
LL | fn bar<T>() -> MustBeCopy<T>
   |                ^^^^^^^^^^^^^ the trait `Copy` is not implemented for `T`
   |
note: required by a bound in `MustBeCopy`
  --> $DIR/wf-in-fn-ret.rs:6:22
   |
LL | struct MustBeCopy<T: Copy> {
   |                      ^^^^ required by this bound in `MustBeCopy`
help: consider restricting type parameter `T`
   |
LL | fn bar<T: std::marker::Copy>() -> MustBeCopy<T>
   |         +++++++++++++++++++

error[E0308]: mismatched types
  --> $DIR/wf-in-fn-ret.rs:10:16
   |
LL | fn bar<T>() -> MustBeCopy<T>
   |    ---         ^^^^^^^^^^^^^ expected `MustBeCopy<T>`, found `()`
   |    |
   |    implicitly returns `()` as its body has no tail or `return` expression
   |
   = note: expected struct `MustBeCopy<T>`
           found unit type `()`

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.