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Auto merge of rust-lang#136111 - jhpratt:rollup-p9wdze6, r=jhpratt
Rollup of 5 pull requests Successful merges: - rust-lang#135807 (Implement phantom variance markers) - rust-lang#136091 (Add some tracing to core bootstrap logic) - rust-lang#136094 (Upgrade elsa to the newest version.) - rust-lang#136097 (rustc_ast: replace some len-checks + indexing with slice patterns etc.) - rust-lang#136101 (triagebot: set myself on vacation) r? `@ghost` `@rustbot` modify labels: rollup
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,260 @@ | ||
| #![unstable(feature = "phantom_variance_markers", issue = "135806")] | ||
|
|
||
| use super::PhantomData; | ||
| use crate::any::type_name; | ||
| use crate::cmp::Ordering; | ||
| use crate::fmt; | ||
| use crate::hash::{Hash, Hasher}; | ||
|
|
||
| macro_rules! first_token { | ||
| ($first:tt $($rest:tt)*) => { | ||
| $first | ||
| }; | ||
| } | ||
|
|
||
| macro_rules! phantom_type { | ||
| ($( | ||
| $(#[$attr:meta])* | ||
| pub struct $name:ident <$t:ident> ($($inner:tt)*); | ||
| )*) => {$( | ||
| $(#[$attr])* | ||
| pub struct $name<$t>($($inner)*) where T: ?Sized; | ||
|
|
||
| impl<T> $name<T> | ||
| where T: ?Sized | ||
| { | ||
| /// Constructs a new instance of the variance marker. | ||
| pub const fn new() -> Self { | ||
| Self(PhantomData) | ||
| } | ||
| } | ||
|
|
||
| impl<T> self::sealed::Sealed for $name<T> where T: ?Sized { | ||
| const VALUE: Self = Self::new(); | ||
| } | ||
| impl<T> Variance for $name<T> where T: ?Sized {} | ||
|
|
||
| impl<T> Default for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn default() -> Self { | ||
| Self(PhantomData) | ||
| } | ||
| } | ||
|
|
||
| impl<T> fmt::Debug for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| write!(f, "{}<{}>", stringify!($name), type_name::<T>()) | ||
| } | ||
| } | ||
|
|
||
| impl<T> Clone for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn clone(&self) -> Self { | ||
| *self | ||
| } | ||
| } | ||
|
|
||
| impl<T> Copy for $name<T> where T: ?Sized {} | ||
|
|
||
| impl<T> PartialEq for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn eq(&self, _: &Self) -> bool { | ||
| true | ||
| } | ||
| } | ||
|
|
||
| impl<T> Eq for $name<T> where T: ?Sized {} | ||
|
|
||
| impl<T> PartialOrd for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn partial_cmp(&self, _: &Self) -> Option<Ordering> { | ||
| Some(Ordering::Equal) | ||
| } | ||
| } | ||
|
|
||
| impl<T> Ord for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn cmp(&self, _: &Self) -> Ordering { | ||
| Ordering::Equal | ||
| } | ||
| } | ||
|
|
||
| impl<T> Hash for $name<T> | ||
| where T: ?Sized | ||
| { | ||
| fn hash<H: Hasher>(&self, _: &mut H) {} | ||
| } | ||
| )*}; | ||
| } | ||
|
|
||
| macro_rules! phantom_lifetime { | ||
| ($( | ||
| $(#[$attr:meta])* | ||
| pub struct $name:ident <$lt:lifetime> ($($inner:tt)*); | ||
| )*) => {$( | ||
| $(#[$attr])* | ||
| #[derive(Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)] | ||
| pub struct $name<$lt>($($inner)*); | ||
|
|
||
| impl $name<'_> { | ||
| /// Constructs a new instance of the variance marker. | ||
| pub const fn new() -> Self { | ||
| Self(first_token!($($inner)*)(PhantomData)) | ||
| } | ||
| } | ||
|
|
||
| impl self::sealed::Sealed for $name<'_> { | ||
| const VALUE: Self = Self::new(); | ||
| } | ||
| impl Variance for $name<'_> {} | ||
|
|
||
| impl fmt::Debug for $name<'_> { | ||
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| write!(f, "{}", stringify!($name)) | ||
| } | ||
| } | ||
| )*}; | ||
| } | ||
|
|
||
| phantom_lifetime! { | ||
| /// Zero-sized type used to mark a lifetime as covariant. | ||
| /// | ||
| /// Covariant lifetimes must live at least as long as declared. See [the reference][1] for more | ||
| /// information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `'a`, the following are guaranteed: | ||
| /// * `size_of::<PhantomCovariantLifetime<'a>>() == 0` | ||
| /// * `align_of::<PhantomCovariantLifetime<'a>>() == 1` | ||
| pub struct PhantomCovariantLifetime<'a>(PhantomCovariant<&'a ()>); | ||
| /// Zero-sized type used to mark a lifetime as contravariant. | ||
| /// | ||
| /// Contravariant lifetimes must live at most as long as declared. See [the reference][1] for | ||
| /// more information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `'a`, the following are guaranteed: | ||
| /// * `size_of::<PhantomContravariantLifetime<'a>>() == 0` | ||
| /// * `align_of::<PhantomContravariantLifetime<'a>>() == 1` | ||
| pub struct PhantomContravariantLifetime<'a>(PhantomContravariant<&'a ()>); | ||
| /// Zero-sized type used to mark a lifetime as invariant. | ||
| /// | ||
| /// Invariant lifetimes must be live for the exact length declared, neither shorter nor longer. | ||
| /// See [the reference][1] for more information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `'a`, the following are guaranteed: | ||
| /// * `size_of::<PhantomInvariantLifetime<'a>>() == 0` | ||
| /// * `align_of::<PhantomInvariantLifetime<'a>>() == 1` | ||
| pub struct PhantomInvariantLifetime<'a>(PhantomInvariant<&'a ()>); | ||
| } | ||
|
|
||
| phantom_type! { | ||
| /// Zero-sized type used to mark a type parameter as covariant. | ||
| /// | ||
| /// Types used as part of the return value from a function are covariant. If the type is _also_ | ||
| /// passed as a parameter then it is [invariant][PhantomInvariant]. See [the reference][1] for | ||
| /// more information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `T`, the following are guaranteed: | ||
| /// * `size_of::<PhantomCovariant<T>>() == 0` | ||
| /// * `align_of::<PhantomCovariant<T>>() == 1` | ||
| pub struct PhantomCovariant<T>(PhantomData<fn() -> T>); | ||
| /// Zero-sized type used to mark a type parameter as contravariant. | ||
| /// | ||
| /// Types passed as arguments to a function are contravariant. If the type is _also_ part of the | ||
| /// return value from a function then it is [invariant][PhantomInvariant]. See [the | ||
| /// reference][1] for more information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `T`, the following are guaranteed: | ||
| /// * `size_of::<PhantomContravariant<T>>() == 0` | ||
| /// * `align_of::<PhantomContravariant<T>>() == 1` | ||
| pub struct PhantomContravariant<T>(PhantomData<fn(T)>); | ||
| /// Zero-sized type used to mark a type parameter as invariant. | ||
| /// | ||
| /// Types that are both passed as an argument _and_ used as part of the return value from a | ||
| /// function are invariant. See [the reference][1] for more information. | ||
| /// | ||
| /// [1]: https://doc.rust-lang.org/stable/reference/subtyping.html#variance | ||
| /// | ||
| /// ## Layout | ||
| /// | ||
| /// For all `T`, the following are guaranteed: | ||
| /// * `size_of::<PhantomInvariant<T>>() == 0` | ||
| /// * `align_of::<PhantomInvariant<T>>() == 1` | ||
| pub struct PhantomInvariant<T>(PhantomData<fn(T) -> T>); | ||
| } | ||
|
|
||
| mod sealed { | ||
| pub trait Sealed { | ||
| const VALUE: Self; | ||
| } | ||
| } | ||
|
|
||
| /// A marker trait for phantom variance types. | ||
| pub trait Variance: sealed::Sealed + Default {} | ||
|
|
||
| /// Construct a variance marker; equivalent to [`Default::default`]. | ||
| /// | ||
| /// This type can be any of the following. You generally should not need to explicitly name the | ||
| /// type, however. | ||
| /// | ||
| /// - [`PhantomCovariant`] | ||
| /// - [`PhantomContravariant`] | ||
| /// - [`PhantomInvariant`] | ||
| /// - [`PhantomCovariantLifetime`] | ||
| /// - [`PhantomContravariantLifetime`] | ||
| /// - [`PhantomInvariantLifetime`] | ||
| /// | ||
| /// # Example | ||
| /// | ||
| /// ```rust | ||
| /// #![feature(phantom_variance_markers)] | ||
| /// | ||
| /// use core::marker::{PhantomCovariant, variance}; | ||
| /// | ||
| /// struct BoundFn<F, P, R> | ||
| /// where | ||
| /// F: Fn(P) -> R, | ||
| /// { | ||
| /// function: F, | ||
| /// parameter: P, | ||
| /// return_value: PhantomCovariant<R>, | ||
| /// } | ||
| /// | ||
| /// let bound_fn = BoundFn { | ||
| /// function: core::convert::identity, | ||
| /// parameter: 5u8, | ||
| /// return_value: variance(), | ||
| /// }; | ||
| /// ``` | ||
| pub const fn variance<T>() -> T | ||
| where | ||
| T: Variance, | ||
| { | ||
| T::VALUE | ||
| } |
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