diff options
| -rw-r--r-- | compiler/rustc_span/src/symbol.rs | 1 | ||||
| -rw-r--r-- | library/core/src/pin.rs | 137 | ||||
| -rw-r--r-- | library/coretests/tests/pin_macro.rs | 1 | ||||
| -rw-r--r-- | tests/ui/feature-gates/feature-gate-unsafe_pin_internals.rs | 16 | ||||
| -rw-r--r-- | tests/ui/feature-gates/feature-gate-unsafe_pin_internals.stderr | 15 | ||||
| -rw-r--r-- | tests/ui/pin-macro/cant_access_internals.rs | 12 | ||||
| -rw-r--r-- | tests/ui/pin-macro/cant_access_internals.stderr | 12 |
7 files changed, 36 insertions, 158 deletions
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index d1f3eb16e4e..4f6e64dc127 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -2215,7 +2215,6 @@ symbols! { unsafe_extern_blocks, unsafe_fields, unsafe_no_drop_flag, - unsafe_pin_internals, unsafe_pinned, unsafe_unpin, unsize, diff --git a/library/core/src/pin.rs b/library/core/src/pin.rs index 48ed5ae451e..9e6acf04bf7 100644 --- a/library/core/src/pin.rs +++ b/library/core/src/pin.rs @@ -1092,24 +1092,15 @@ pub use self::unsafe_pinned::UnsafePinned; #[rustc_pub_transparent] #[derive(Copy, Clone)] pub struct Pin<Ptr> { - // FIXME(#93176): this field is made `#[unstable] #[doc(hidden)] pub` to: - // - deter downstream users from accessing it (which would be unsound!), - // - let the `pin!` macro access it (such a macro requires using struct - // literal syntax in order to benefit from lifetime extension). - // - // However, if the `Deref` impl exposes a field with the same name as this - // field, then the two will collide, resulting in a confusing error when the - // user attempts to access the field through a `Pin<Ptr>`. Therefore, the - // name `__pointer` is designed to be unlikely to collide with any other - // field. Long-term, macro hygiene is expected to offer a more robust - // alternative, alongside `unsafe` fields. - #[unstable(feature = "unsafe_pin_internals", issue = "none")] - #[doc(hidden)] - pub __pointer: Ptr, + /// Only public for bootstrap. + #[cfg(bootstrap)] + pub pointer: Ptr, + #[cfg(not(bootstrap))] + pointer: Ptr, } // The following implementations aren't derived in order to avoid soundness -// issues. `&self.__pointer` should not be accessible to untrusted trait +// issues. `&self.pointer` should not be accessible to untrusted trait // implementations. // // See <https://internals.rust-lang.org/t/unsoundness-in-pin/11311/73> for more details. @@ -1223,7 +1214,7 @@ impl<Ptr: Deref<Target: Unpin>> Pin<Ptr> { #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] #[stable(feature = "pin_into_inner", since = "1.39.0")] pub const fn into_inner(pin: Pin<Ptr>) -> Ptr { - pin.__pointer + pin.pointer } } @@ -1360,7 +1351,7 @@ impl<Ptr: Deref> Pin<Ptr> { #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] #[stable(feature = "pin", since = "1.33.0")] pub const unsafe fn new_unchecked(pointer: Ptr) -> Pin<Ptr> { - Pin { __pointer: pointer } + Pin { pointer } } /// Gets a shared reference to the pinned value this [`Pin`] points to. @@ -1374,7 +1365,7 @@ impl<Ptr: Deref> Pin<Ptr> { #[inline(always)] pub fn as_ref(&self) -> Pin<&Ptr::Target> { // SAFETY: see documentation on this function - unsafe { Pin::new_unchecked(&*self.__pointer) } + unsafe { Pin::new_unchecked(&*self.pointer) } } } @@ -1418,7 +1409,7 @@ impl<Ptr: DerefMut> Pin<Ptr> { #[inline(always)] pub fn as_mut(&mut self) -> Pin<&mut Ptr::Target> { // SAFETY: see documentation on this function - unsafe { Pin::new_unchecked(&mut *self.__pointer) } + unsafe { Pin::new_unchecked(&mut *self.pointer) } } /// Gets `Pin<&mut T>` to the underlying pinned value from this nested `Pin`-pointer. @@ -1485,7 +1476,7 @@ impl<Ptr: DerefMut> Pin<Ptr> { where Ptr::Target: Sized, { - *(self.__pointer) = value; + *(self.pointer) = value; } } @@ -1513,7 +1504,7 @@ impl<Ptr: Deref> Pin<Ptr> { #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] #[stable(feature = "pin_into_inner", since = "1.39.0")] pub const unsafe fn into_inner_unchecked(pin: Pin<Ptr>) -> Ptr { - pin.__pointer + pin.pointer } } @@ -1539,7 +1530,7 @@ impl<'a, T: ?Sized> Pin<&'a T> { U: ?Sized, F: FnOnce(&T) -> &U, { - let pointer = &*self.__pointer; + let pointer = &*self.pointer; let new_pointer = func(pointer); // SAFETY: the safety contract for `new_unchecked` must be @@ -1569,7 +1560,7 @@ impl<'a, T: ?Sized> Pin<&'a T> { #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] #[stable(feature = "pin", since = "1.33.0")] pub const fn get_ref(self) -> &'a T { - self.__pointer + self.pointer } } @@ -1580,7 +1571,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> { #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] #[stable(feature = "pin", since = "1.33.0")] pub const fn into_ref(self) -> Pin<&'a T> { - Pin { __pointer: self.__pointer } + Pin { pointer: self.pointer } } /// Gets a mutable reference to the data inside of this `Pin`. @@ -1600,7 +1591,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> { where T: Unpin, { - self.__pointer + self.pointer } /// Gets a mutable reference to the data inside of this `Pin`. @@ -1618,7 +1609,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> { #[stable(feature = "pin", since = "1.33.0")] #[rustc_const_stable(feature = "const_pin", since = "1.84.0")] pub const unsafe fn get_unchecked_mut(self) -> &'a mut T { - self.__pointer + self.pointer } /// Constructs a new pin by mapping the interior value. @@ -1705,21 +1696,21 @@ impl<Ptr: LegacyReceiver> LegacyReceiver for Pin<Ptr> {} #[stable(feature = "pin", since = "1.33.0")] impl<Ptr: fmt::Debug> fmt::Debug for Pin<Ptr> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Debug::fmt(&self.__pointer, f) + fmt::Debug::fmt(&self.pointer, f) } } #[stable(feature = "pin", since = "1.33.0")] impl<Ptr: fmt::Display> fmt::Display for Pin<Ptr> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Display::fmt(&self.__pointer, f) + fmt::Display::fmt(&self.pointer, f) } } #[stable(feature = "pin", since = "1.33.0")] impl<Ptr: fmt::Pointer> fmt::Pointer for Pin<Ptr> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - fmt::Pointer::fmt(&self.__pointer, f) + fmt::Pointer::fmt(&self.pointer, f) } } @@ -1945,80 +1936,22 @@ unsafe impl<T: ?Sized> PinCoerceUnsized for *mut T {} /// constructor. /// /// [`Box::pin`]: ../../std/boxed/struct.Box.html#method.pin +#[cfg(not(bootstrap))] #[stable(feature = "pin_macro", since = "1.68.0")] #[rustc_macro_transparency = "semitransparent"] -#[allow_internal_unstable(unsafe_pin_internals)] -#[rustc_macro_edition_2021] +#[allow_internal_unstable(super_let)] pub macro pin($value:expr $(,)?) { - // This is `Pin::new_unchecked(&mut { $value })`, so, for starters, let's - // review such a hypothetical macro (that any user-code could define): - // - // ```rust - // macro_rules! pin {( $value:expr ) => ( - // match &mut { $value } { at_value => unsafe { // Do not wrap `$value` in an `unsafe` block. - // $crate::pin::Pin::<&mut _>::new_unchecked(at_value) - // }} - // )} - // ``` - // - // Safety: - // - `type P = &mut _`. There are thus no pathological `Deref{,Mut}` impls - // that would break `Pin`'s invariants. - // - `{ $value }` is braced, making it a _block expression_, thus **moving** - // the given `$value`, and making it _become an **anonymous** temporary_. - // By virtue of being anonymous, it can no longer be accessed, thus - // preventing any attempts to `mem::replace` it or `mem::forget` it, _etc._ - // - // This gives us a `pin!` definition that is sound, and which works, but only - // in certain scenarios: - // - If the `pin!(value)` expression is _directly_ fed to a function call: - // `let poll = pin!(fut).poll(cx);` - // - If the `pin!(value)` expression is part of a scrutinee: - // ```rust - // match pin!(fut) { pinned_fut => { - // pinned_fut.as_mut().poll(...); - // pinned_fut.as_mut().poll(...); - // }} // <- `fut` is dropped here. - // ``` - // Alas, it doesn't work for the more straight-forward use-case: `let` bindings. - // ```rust - // let pinned_fut = pin!(fut); // <- temporary value is freed at the end of this statement - // pinned_fut.poll(...) // error[E0716]: temporary value dropped while borrowed - // // note: consider using a `let` binding to create a longer lived value - // ``` - // - Issues such as this one are the ones motivating https://github.com/rust-lang/rfcs/pull/66 - // - // This makes such a macro incredibly unergonomic in practice, and the reason most macros - // out there had to take the path of being a statement/binding macro (_e.g._, `pin!(future);`) - // instead of featuring the more intuitive ergonomics of an expression macro. - // - // Luckily, there is a way to avoid the problem. Indeed, the problem stems from the fact that a - // temporary is dropped at the end of its enclosing statement when it is part of the parameters - // given to function call, which has precisely been the case with our `Pin::new_unchecked()`! - // For instance, - // ```rust - // let p = Pin::new_unchecked(&mut <temporary>); - // ``` - // becomes: - // ```rust - // let p = { let mut anon = <temporary>; &mut anon }; - // ``` - // - // However, when using a literal braced struct to construct the value, references to temporaries - // can then be taken. This makes Rust change the lifespan of such temporaries so that they are, - // instead, dropped _at the end of the enscoping block_. - // For instance, - // ```rust - // let p = Pin { __pointer: &mut <temporary> }; - // ``` - // becomes: - // ```rust - // let mut anon = <temporary>; - // let p = Pin { __pointer: &mut anon }; - // ``` - // which is *exactly* what we want. - // - // See https://doc.rust-lang.org/1.58.1/reference/destructors.html#temporary-lifetime-extension - // for more info. - $crate::pin::Pin::<&mut _> { __pointer: &mut { $value } } + { + super let mut pinned = $value; + // SAFETY: The value is pinned: it is the local above which cannot be named outside this macro. + unsafe { $crate::pin::Pin::new_unchecked(&mut pinned) } + } +} + +/// Only for bootstrap. +#[cfg(bootstrap)] +#[stable(feature = "pin_macro", since = "1.68.0")] +#[rustc_macro_transparency = "semitransparent"] +pub macro pin($value:expr $(,)?) { + $crate::pin::Pin::<&mut _> { pointer: &mut { $value } } } diff --git a/library/coretests/tests/pin_macro.rs b/library/coretests/tests/pin_macro.rs index bfbfa8d280f..3174c91a649 100644 --- a/library/coretests/tests/pin_macro.rs +++ b/library/coretests/tests/pin_macro.rs @@ -38,6 +38,7 @@ fn rust_2024_expr() { } #[test] +#[cfg(not(bootstrap))] fn temp_lifetime() { // Check that temporary lifetimes work as in Rust 2021. // Regression test for https://github.com/rust-lang/rust/issues/138596 diff --git a/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.rs b/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.rs deleted file mode 100644 index deb5a2f691b..00000000000 --- a/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.rs +++ /dev/null @@ -1,16 +0,0 @@ -//@ edition:2018 -#![forbid(internal_features, unsafe_code)] -#![feature(unsafe_pin_internals)] -//~^ ERROR the feature `unsafe_pin_internals` is internal to the compiler or standard library - -use core::{marker::PhantomPinned, pin::Pin}; - -/// The `unsafe_pin_internals` is indeed unsound. -fn non_unsafe_pin_new_unchecked<T>(pointer: &mut T) -> Pin<&mut T> { - Pin { __pointer: pointer } -} - -fn main() { - let mut self_referential = PhantomPinned; - let _: Pin<&mut PhantomPinned> = non_unsafe_pin_new_unchecked(&mut self_referential); -} diff --git a/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.stderr b/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.stderr deleted file mode 100644 index fc9bcd90e52..00000000000 --- a/tests/ui/feature-gates/feature-gate-unsafe_pin_internals.stderr +++ /dev/null @@ -1,15 +0,0 @@ -error: the feature `unsafe_pin_internals` is internal to the compiler or standard library - --> $DIR/feature-gate-unsafe_pin_internals.rs:3:12 - | -LL | #![feature(unsafe_pin_internals)] - | ^^^^^^^^^^^^^^^^^^^^ - | - = note: using it is strongly discouraged -note: the lint level is defined here - --> $DIR/feature-gate-unsafe_pin_internals.rs:2:11 - | -LL | #![forbid(internal_features, unsafe_code)] - | ^^^^^^^^^^^^^^^^^ - -error: aborting due to 1 previous error - diff --git a/tests/ui/pin-macro/cant_access_internals.rs b/tests/ui/pin-macro/cant_access_internals.rs deleted file mode 100644 index 36a47d0fdf9..00000000000 --- a/tests/ui/pin-macro/cant_access_internals.rs +++ /dev/null @@ -1,12 +0,0 @@ -//@ edition:2018 - -use core::{ - marker::PhantomPinned, - mem, - pin::{pin, Pin}, -}; - -fn main() { - let mut phantom_pinned = pin!(PhantomPinned); - mem::take(phantom_pinned.__pointer); //~ ERROR use of unstable library feature `unsafe_pin_internals` -} diff --git a/tests/ui/pin-macro/cant_access_internals.stderr b/tests/ui/pin-macro/cant_access_internals.stderr deleted file mode 100644 index 8ad897bbbb9..00000000000 --- a/tests/ui/pin-macro/cant_access_internals.stderr +++ /dev/null @@ -1,12 +0,0 @@ -error[E0658]: use of unstable library feature `unsafe_pin_internals` - --> $DIR/cant_access_internals.rs:11:15 - | -LL | mem::take(phantom_pinned.__pointer); - | ^^^^^^^^^^^^^^^^^^^^^^^^ - | - = help: add `#![feature(unsafe_pin_internals)]` to the crate attributes to enable - = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date - -error: aborting due to 1 previous error - -For more information about this error, try `rustc --explain E0658`. |