error[E0277]: the size for values of type `T` cannot be known at compilation time --> $DIR/const-argument-if-length.rs:15:12 | LL | pub struct AtLeastByte { | - this type parameter needs to be `std::marker::Sized` LL | value: T, | ^ doesn't have a size known at compile-time | = note: only the last field of a struct may have a dynamically sized type = help: change the field's type to have a statically known size help: consider removing the `?Sized` bound to make the type parameter `Sized` | LL - pub struct AtLeastByte { LL + pub struct AtLeastByte { | help: borrowed types always have a statically known size | LL | value: &T, | + help: the `Box` type always has a statically known size and allocates its contents in the heap | LL | value: Box, | ++++ + error: unconstrained generic constant --> $DIR/const-argument-if-length.rs:17:10 | LL | pad: [u8; is_zst::()], | ^^^^^^^^^^^^^^^^^^^ | = help: try adding a `where` bound using this expression: `where [(); is_zst::()]:` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.