error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time --> $DIR/issue-5883.rs:17:15 | LL | fn new_struct(r: 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 = 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:18:8 | LL | -> Struct { //~^ ERROR the size for values of type | ^^^^^^ doesn't have a size known at compile-time | = help: within `Struct`, the trait `std::marker::Sized` is not implemented for `(dyn A + 'static)` = note: to learn more, visit = 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`.