Promotion is not allowed to throw away side effects.
This includes panicking. So in order to promote &(0_usize - 1),
the subtraction is thrown away and only the panic is kept.
Only const safe code gets promoted. This means that promotion doesn't happen if the code does some action which, when run at compile time, either errors or produces a value that differs from runtime.
An example of this would be &1 as *const i32 as usize == 42. While it is highly
unlikely that the address of temporary value is 42, at runtime this could be true.
The exact details for const safety are discussed in here.