munge
makes it easy and safe to destructure MaybeUninit
s, Cell
s,
UnsafeCell
s, ManuallyDrop
s, and more.
Just use the munge!
macro to destructure opaque types the same way you'd
destructure a value. The munge!
macro may be used to perform either borrow
destructuring (e.g. let (a, b) = c
where c
is a reference) or move
destructuring (e.g. let (a, b) = c
where c
is a value) depending on the
type.
munge
has no features and is always #![no_std]
.
Examples
munge
makes it easy to initialize MaybeUninit
s:
use ;
let mut mu = uninit;
munge!;
assert_eq!;
assert_eq!;
assert_eq!;
// Note that `mut` bindings can be reassigned like you'd expect:
f = &mut uninit;
// SAFETY: `mu` is completely initialized.
let init = unsafe ;
assert_eq!;
assert_eq!;
assert_eq!;
It can also be used to destructure Cell
s:
use ;
let value = Example ;
let cell = new;
munge!;
assert_eq!;
a.set;
assert_eq!;
c.set;
assert_eq!;
f.set;
let value = cell.into_inner;
assert_eq!;
assert_eq!;
assert_eq!;
You can even extend munge
to work with your own types by implementing its
Destructure
and Restructure
traits:
use ;
;
// SAFETY:
// - `Invariant<T>` is destructured by move, so its `Destructuring` type is
// `Move`.
// - `underlying` returns a pointer to its inner type, so it is guaranteed
// to be non-null, properly aligned, and valid for reads.
unsafe
// SAFETY: `restructure` returns an `Invariant<U>` that takes ownership of
// the restructured field because `Invariant<T>` is destructured by move.
unsafe
// SAFETY: `(1, 2, 3)` upholds my custom invariant.
let value = unsafe ;
munge!;
assert_eq!;
assert_eq!;
assert_eq!;