| A cast between a thin and a wide pointer was attempted. |
| |
| Erroneous code example: |
| |
| ```compile_fail,E0607 |
| let v = core::ptr::null::<u8>(); |
| v as *const [u8]; |
| ``` |
| |
| First: what are thin and wide pointers? |
| |
| Thin pointers are "simple" pointers: they are purely a reference to a memory |
| address. |
| |
| Wide pointers are pointers referencing Dynamically Sized Types (also called |
| DSTs). DSTs don't have a statically known size, therefore they can only exist |
| behind some kind of pointer that contains additional information. For example, |
| slices and trait objects are DSTs. In the case of slices, the additional |
| information the wide pointer holds is their size. |
| |
| To fix this error, don't try to cast directly between thin and wide pointers. |
| |
| For more information about type casts, take a look at the section of the |
| [The Rust Reference][1] on type cast expressions. |
| |
| [1]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#type-cast-expressions |
