error[E0277]: `PhantomPinned` cannot be unpinned
  --> $DIR/add-pinned-field.rs:21:5
   |
4  | fn is_unpin<T: Unpin>() {}
   |                ----- required by this bound in `is_unpin`
...
21 |     is_unpin::<Foo>(); //~ ERROR E0277
   |     ^^^^^^^^^^^^^^^ within `__Foo<'_>`, the trait `Unpin` is not implemented for `PhantomPinned`
   |
   = note: consider using `Box::pin`
note: required because it appears within the type `__Foo<'_>`
  --> $DIR/add-pinned-field.rs:8:8
   |
8  | struct Foo {
   |        ^^^
   = note: required because of the requirements on the impl of `Unpin` for `Foo`

error[E0277]: `PhantomPinned` cannot be unpinned
  --> $DIR/add-pinned-field.rs:22:5
   |
4  | fn is_unpin<T: Unpin>() {}
   |                ----- required by this bound in `is_unpin`
...
22 |     is_unpin::<Bar>(); //~ ERROR E0277
   |     ^^^^^^^^^^^^^^^ within `__Bar<'_>`, the trait `Unpin` is not implemented for `PhantomPinned`
   |
   = note: consider using `Box::pin`
note: required because it appears within the type `__Bar<'_>`
  --> $DIR/add-pinned-field.rs:15:8
   |
15 | struct Bar {
   |        ^^^
   = note: required because of the requirements on the impl of `Unpin` for `Bar`