error: Undefined Behavior: enum value has invalid tag: 0xff
  --> tests/fail/validity/invalid_enum_cast.rs:LL:CC
   |
LL |         let _val = *ptr as u32;
   |                    ^^^^^^^^^^^ Undefined Behavior occurred here
   |
   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
   = note: BACKTRACE:
   = note: inside `cast` at tests/fail/validity/invalid_enum_cast.rs:LL:CC
note: inside `main`
  --> tests/fail/validity/invalid_enum_cast.rs:LL:CC
   |
LL |     cast(&v as *const u32 as *const E);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace

error: aborting due to 1 previous error