Why does Rust does not allow creating a slice sa as a value {ptr, len} on the stack and only allows to create rsa as a references to some (anonymous?) value called a fat pointer?
// a is five i32 values on the stack
let a = [1, 2, 3, 4, 5];
// rsa is a reference to (anonymous?) {ptr,len} on the stack
let rsa = &a[..];
// sa would be an explicit struct {ptr,len} on the stack
let sa = a[..];
error[E0277]: the size for values of type `[{integer}]` cannot be known at compilation time
--> src/main.rs:9:9
|
9 | let sa = a[..];
| ^^ ----- help: consider borrowing here: `&a[..]`
| |
| doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `[{integer}]`
= 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