error[E0277]: the size for values of type `str` cannot be known at compilation time --> $DIR/union-unsized.rs:5:8 | LL | a: str, | ^^^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `str` = note: no field of a union may have a dynamically sized type = help: change the field's type to have a statically known size help: borrowed types always have a statically known size | LL | a: &str, | + help: the `Box` type always has a statically known size and allocates its contents in the heap | LL | a: Box, | ++++ + error[E0277]: the size for values of type `str` cannot be known at compilation time --> $DIR/union-unsized.rs:13:8 | LL | b: str, | ^^^ doesn't have a size known at compile-time | = help: the trait `Sized` is not implemented for `str` = note: no field of a union may have a dynamically sized type = help: change the field's type to have a statically known size help: borrowed types always have a statically known size | LL | b: &str, | + help: the `Box` type always has a statically known size and allocates its contents in the heap | LL | b: Box, | ++++ + error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.