error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
  --> $DIR/issue-5883.rs:7:15
   |
LL | fn new_struct(r: dyn A + 'static)
   |               ^ doesn't have a size known at compile-time
   |
   = help: the trait `std::marker::Sized` is not implemented for `(dyn A + 'static)`
   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: all local variables must have a statically known size
   = help: unsized locals are gated as an unstable feature

error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
  --> $DIR/issue-5883.rs:8:8
   |
LL |     -> Struct {
   |        ^^^^^^ doesn't have a size known at compile-time
LL |
LL |     Struct { r: r }
   |     --------------- this returned value is of type `Struct`
   |
   = help: within `Struct`, the trait `std::marker::Sized` is not implemented for `(dyn A + 'static)`
   = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required because it appears within the type `Struct`
   = note: the return type of a function must have a statically known size

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0277`.