Drop

- Drop is eager (unlike in Rust)
- Drop is for "infallible" memory management, using is for actual resources
- Drop also runs as a "finaliser"
- (e.g. Drop on an Array deallocates the memory)
- no drop flags needed because no partial initialisation + eager drop
- Drop is not lowered to JS (not sure how that would even work..?)
- owned locals drop after their last use, owned fields drop with their parent, and managed allocations run Drop when reclaimed

export newtype interface Drop {
    /// Drop this value.
    drop(&exclusive this): void;
}
- Drop is a finalizer, yes, but a very restricted one
- no allocations, no panics, statically checked

- no drop flags
- maybe-present values use explicit unions; conditional moves are rejected at control-flow joins, so runtime drop flags are unnecessary
- drop(value) ends ownership immediately
- forget(value) suppresses automatic drop
- ManuallyDrop<T> stores outside automatic drop
- and Box<T>.leak() yields a static borrow