pub unsafe fn mw_unchecked(&self, addr: Address<F>, val: Block<F>) {
        match self.0.get(addr.as_usize()).map(|c| unsafe {
            // SAFETY: The pointer is dereferenceable. There are no other aliases to the data
            // because of the happens-before relation (no other `mw_unchecked` can be invoked on
            // the same address, and this call happens-before any `mr_unchecked`.)
            // The mutable/shared reference is dropped below, so it does not escape with
            // an invalid lifetime.
            &mut *c.0.get()
        }) {
            // This does not leak memory because the address is written to exactly once.
            // Leaking is memory-safe in Rust, so this isn't technically a "SAFETY" comment.
            Some(entry) => drop(entry.write(MemoryEntry { val })),
            None => panic!(
                "expected address {} to be less than length {}",
                addr.as_usize(),
                self.0.len()
            ),
        }
    }
# Safety
This should be called precisely when memory is to be written according to a happens-before
relation corresponding to the documented invariants of [`crate::RecursionProgram`]
invariants. This guarantees the absence of any data races.
crates/recursion/core/src/runtime/memory.rs