error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> tests/ui-msrv/transmute-mut-dst-unsized.rs:17:32
   |
17 | const DST_UNSIZED: &mut [u8] = transmute_mut!(&mut [0u8; 1]);
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `[u8]`
   = note: this error originates in the macro `transmute_mut` (in Nightly builds, run with -Z macro-backtrace for more info)