fn assert_failed(at: usize, len: usize) -> ! {
            panic!("`at` split index (is {}) should be <= len (is {})", at, len);
        }
Consumes and leaks the `Vec`, returning a mutable reference to the contents,
`&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime
`'a`. If the type has only static references, or none at all, then this
may be chosen to be `'static`.

This function is similar to the [`leak`][Box::leak] function on [`Box`]
except that there is no way to recover the leaked memory.

This function is mainly useful for data that lives for the remainder of
th
benchmarks/haystacks/code/rust-library.rs