Consider the following function:
fn make_array<T>()
where
T: Sized,
{
let bytes = [0u8; std::mem::size_of::<T>()];
}
For whatever reason it fails to compile
error[E0277]: the size for values of type `T` cannot be known at compilation time
--> src/lib.rs:5:23
|
5 | let bytes = [0u8; std::mem::size_of::<T>()];
| ^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `T`
= note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= help: consider adding a `where T: std::marker::Sized` bound
= note: required by `std::mem::size_of`
This is despite the fact that there is a Sized
trait bound for the generic parameter T
. It doesn't make any sense to me.
Why is this happening and how do I work around it?
It seems to be bug #43408: Array lengths don't support generic parameters.
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