Rollup merge of #76655 - CDirkx:const-pin, r=ecstatic-morse
Make some methods of `Pin` unstable const Make the following methods unstable const under the `const_pin` feature: - `new` - `new_unchecked` - `into_inner` - `into_inner_unchecked` - `get_ref` - `into_ref` - `get_mut` - `get_unchecked_mut` Of these, `into_inner` and `into_inner_unchecked` require the unstable `const_precise_live_drops`. Also adds tests for these methods in a const context. Tracking issue: #76654 r? @ecstatic-morse
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commit
537ede465f
4 changed files with 59 additions and 16 deletions
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@ -78,6 +78,7 @@
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#![feature(const_int_pow)]
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#![feature(constctlz)]
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#![feature(const_panic)]
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#![feature(const_pin)]
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#![feature(const_fn_union)]
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#![feature(const_generics)]
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#![feature(const_option)]
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@ -471,9 +471,10 @@ impl<P: Deref<Target: Unpin>> Pin<P> {
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///
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/// Unlike `Pin::new_unchecked`, this method is safe because the pointer
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/// `P` dereferences to an [`Unpin`] type, which cancels the pinning guarantees.
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub fn new(pointer: P) -> Pin<P> {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin", since = "1.33.0")]
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pub const fn new(pointer: P) -> Pin<P> {
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// SAFETY: the value pointed to is `Unpin`, and so has no requirements
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// around pinning.
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unsafe { Pin::new_unchecked(pointer) }
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@ -483,9 +484,10 @@ impl<P: Deref<Target: Unpin>> Pin<P> {
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///
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/// This requires that the data inside this `Pin` is [`Unpin`] so that we
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/// can ignore the pinning invariants when unwrapping it.
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#[stable(feature = "pin_into_inner", since = "1.39.0")]
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#[inline(always)]
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pub fn into_inner(pin: Pin<P>) -> P {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin_into_inner", since = "1.39.0")]
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pub const fn into_inner(pin: Pin<P>) -> P {
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pin.pointer
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}
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}
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@ -556,9 +558,10 @@ impl<P: Deref> Pin<P> {
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///
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/// [`mem::swap`]: crate::mem::swap
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#[lang = "new_unchecked"]
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub unsafe fn new_unchecked(pointer: P) -> Pin<P> {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin", since = "1.33.0")]
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pub const unsafe fn new_unchecked(pointer: P) -> Pin<P> {
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Pin { pointer }
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}
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@ -589,9 +592,10 @@ impl<P: Deref> Pin<P> {
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///
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/// If the underlying data is [`Unpin`], [`Pin::into_inner`] should be used
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/// instead.
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#[stable(feature = "pin_into_inner", since = "1.39.0")]
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#[inline(always)]
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pub unsafe fn into_inner_unchecked(pin: Pin<P>) -> P {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin_into_inner", since = "1.39.0")]
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pub const unsafe fn into_inner_unchecked(pin: Pin<P>) -> P {
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pin.pointer
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}
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}
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@ -693,18 +697,20 @@ impl<'a, T: ?Sized> Pin<&'a T> {
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/// with the same lifetime as the original `Pin`.
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///
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/// ["pinning projections"]: self#projections-and-structural-pinning
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub fn get_ref(self) -> &'a T {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin", since = "1.33.0")]
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pub const fn get_ref(self) -> &'a T {
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self.pointer
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}
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}
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impl<'a, T: ?Sized> Pin<&'a mut T> {
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/// Converts this `Pin<&mut T>` into a `Pin<&T>` with the same lifetime.
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub fn into_ref(self) -> Pin<&'a T> {
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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#[stable(feature = "pin", since = "1.33.0")]
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pub const fn into_ref(self) -> Pin<&'a T> {
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Pin { pointer: self.pointer }
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}
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@ -717,9 +723,10 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
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/// that lives for as long as the borrow of the `Pin`, not the lifetime of
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/// the `Pin` itself. This method allows turning the `Pin` into a reference
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/// with the same lifetime as the original `Pin`.
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub fn get_mut(self) -> &'a mut T
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#[stable(feature = "pin", since = "1.33.0")]
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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pub const fn get_mut(self) -> &'a mut T
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where
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T: Unpin,
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{
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@ -736,9 +743,10 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
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///
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/// If the underlying data is `Unpin`, `Pin::get_mut` should be used
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/// instead.
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#[stable(feature = "pin", since = "1.33.0")]
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#[inline(always)]
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pub unsafe fn get_unchecked_mut(self) -> &'a mut T {
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#[stable(feature = "pin", since = "1.33.0")]
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#[rustc_const_unstable(feature = "const_pin", issue = "76654")]
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pub const unsafe fn get_unchecked_mut(self) -> &'a mut T {
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self.pointer
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}
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@ -43,6 +43,8 @@
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#![feature(iter_order_by)]
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#![feature(cmp_min_max_by)]
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#![feature(iter_map_while)]
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#![feature(const_mut_refs)]
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#![feature(const_pin)]
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#![feature(const_slice_from_raw_parts)]
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#![feature(const_raw_ptr_deref)]
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#![feature(never_type)]
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@ -79,6 +81,7 @@ mod num;
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mod ops;
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mod option;
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mod pattern;
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mod pin;
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mod ptr;
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mod result;
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mod slice;
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31
library/core/tests/pin.rs
Normal file
31
library/core/tests/pin.rs
Normal file
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@ -0,0 +1,31 @@
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use core::pin::Pin;
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#[test]
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fn pin_const() {
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// test that the methods of `Pin` are usable in a const context
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const POINTER: &'static usize = &2;
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const PINNED: Pin<&'static usize> = Pin::new(POINTER);
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const PINNED_UNCHECKED: Pin<&'static usize> = unsafe { Pin::new_unchecked(POINTER) };
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assert_eq!(PINNED_UNCHECKED, PINNED);
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const INNER: &'static usize = Pin::into_inner(PINNED);
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assert_eq!(INNER, POINTER);
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const INNER_UNCHECKED: &'static usize = unsafe { Pin::into_inner_unchecked(PINNED) };
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assert_eq!(INNER_UNCHECKED, POINTER);
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const REF: &'static usize = PINNED.get_ref();
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assert_eq!(REF, POINTER);
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// Note: `pin_mut_const` tests that the methods of `Pin<&mut T>` are usable in a const context.
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// A const fn is used because `&mut` is not (yet) usable in constants.
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const fn pin_mut_const() {
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let _ = Pin::new(&mut 2).into_ref();
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let _ = Pin::new(&mut 2).get_mut();
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let _ = unsafe { Pin::new(&mut 2).get_unchecked_mut() };
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}
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pin_mut_const();
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}
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