error: any use of this value will cause an error
  --> $DIR/transmute-size-mismatch-before-typeck.rs:13:29
   |
LL | const ZST: &[u8] = unsafe { std::mem::transmute(1usize) };
   | ----------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^---
   |                             |
   |                             transmuting `usize` to `&[u8]` is not possible, because these types do not have the same size
   |
   = note: `#[deny(const_err)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>

error: could not evaluate constant pattern
  --> $DIR/transmute-size-mismatch-before-typeck.rs:8:9
   |
LL |         ZST => {}
   |         ^^^

error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
  --> $DIR/transmute-size-mismatch-before-typeck.rs:13:29
   |
LL | const ZST: &[u8] = unsafe { std::mem::transmute(1usize) };
   |                             ^^^^^^^^^^^^^^^^^^^
   |
   = note: source type: `usize` (word size)
   = note: target type: `&[u8]` (2 * word size)

error: could not evaluate constant pattern
  --> $DIR/transmute-size-mismatch-before-typeck.rs:8:9
   |
LL |         ZST => {}
   |         ^^^

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0512`.