diff options
Diffstat (limited to 'library/core/src/marker.rs')
| -rw-r--r-- | library/core/src/marker.rs | 211 |
1 files changed, 145 insertions, 66 deletions
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs index 40789cb3049..47a3e78b4d5 100644 --- a/library/core/src/marker.rs +++ b/library/core/src/marker.rs @@ -12,6 +12,60 @@ use crate::fmt::Debug; use crate::hash::Hash; use crate::hash::Hasher; +/// Implements a given marker trait for multiple types at the same time. +/// +/// The basic syntax looks like this: +/// ```ignore private macro +/// marker_impls! { MarkerTrait for u8, i8 } +/// ``` +/// You can also implement `unsafe` traits +/// ```ignore private macro +/// marker_impls! { unsafe MarkerTrait for u8, i8 } +/// ``` +/// Add attributes to all impls: +/// ```ignore private macro +/// marker_impls! { +/// #[allow(lint)] +/// #[unstable(feature = "marker_trait", issue = "none")] +/// MarkerTrait for u8, i8 +/// } +/// ``` +/// And use generics: +/// ```ignore private macro +/// marker_impls! { +/// MarkerTrait for +/// u8, i8, +/// {T: ?Sized} *const T, +/// {T: ?Sized} *mut T, +/// {T: MarkerTrait} PhantomData<T>, +/// u32, +/// } +/// ``` +#[unstable(feature = "internal_impls_macro", issue = "none")] +macro marker_impls { + ( $(#[$($meta:tt)*])* $Trait:ident for $( $({$($bounds:tt)*})? $T:ty ),+ $(,)?) => { + // This inner macro is needed because... idk macros are weird. + // It allows repeating `meta` on all impls. + #[unstable(feature = "internal_impls_macro", issue = "none")] + macro _impl { + ( $$({$$($$bounds_:tt)*})? $$T_:ty ) => { + $(#[$($meta)*])* impl<$$($$($$bounds_)*)?> $Trait for $$T_ {} + } + } + $( _impl! { $({$($bounds)*})? $T } )+ + }, + ( $(#[$($meta:tt)*])* unsafe $Trait:ident for $( $({$($bounds:tt)*})? $T:ty ),+ $(,)?) => { + #[unstable(feature = "internal_impls_macro", issue = "none")] + macro _impl { + ( $$({$$($$bounds_:tt)*})? $$T_:ty ) => { + $(#[$($meta)*])* unsafe impl<$$($$($$bounds_)*)?> $Trait for $$T_ {} + } + } + + $( _impl! { $({$($bounds)*})? $T } )+ + }, +} + /// Types that can be transferred across thread boundaries. /// /// This trait is automatically implemented when the compiler determines it's @@ -24,7 +78,7 @@ use crate::hash::Hasher; /// operations. Its cousin [`sync::Arc`][arc] does use atomic operations (incurring /// some overhead) and thus is `Send`. /// -/// See [the Nomicon](../../nomicon/send-and-sync.html) for more details. +/// See [the Nomicon](../../nomicon/send-and-sync.html) and the [`Sync`] trait for more details. /// /// [`Rc`]: ../../std/rc/struct.Rc.html /// [arc]: ../../std/sync/struct.Arc.html @@ -214,6 +268,20 @@ pub trait StructuralEq { // Empty. } +// FIXME: Remove special cases of these types from the compiler pattern checking code and always check `T: StructuralEq` instead +marker_impls! { + #[unstable(feature = "structural_match", issue = "31434")] + StructuralEq for + usize, u8, u16, u32, u64, u128, + isize, i8, i16, i32, i64, i128, + bool, + char, + str /* Technically requires `[u8]: StructuralEq` */, + {T, const N: usize} [T; N], + {T} [T], + {T: ?Sized} &T, +} + /// Types whose values can be duplicated simply by copying bits. /// /// By default, variable bindings have 'move semantics.' In other @@ -401,6 +469,30 @@ pub macro Copy($item:item) { /* compiler built-in */ } +// Implementations of `Copy` for primitive types. +// +// Implementations that cannot be described in Rust +// are implemented in `traits::SelectionContext::copy_clone_conditions()` +// in `rustc_trait_selection`. +marker_impls! { + #[stable(feature = "rust1", since = "1.0.0")] + Copy for + usize, u8, u16, u32, u64, u128, + isize, i8, i16, i32, i64, i128, + f32, f64, + bool, char, + {T: ?Sized} *const T, + {T: ?Sized} *mut T, + +} + +#[unstable(feature = "never_type", issue = "35121")] +impl Copy for ! {} + +/// Shared references can be copied, but mutable references *cannot*! +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized> Copy for &T {} + /// Types for which it is safe to share references between threads. /// /// This trait is automatically implemented when the compiler determines @@ -426,6 +518,11 @@ pub macro Copy($item:item) { /// becomes read-only, as if it were a `& &T`. Hence there is no risk /// of a data race. /// +/// A shorter overview of how [`Sync`] and [`Send`] relate to referencing: +/// * `&T` is [`Send`] if and only if `T` is [`Sync`] +/// * `&mut T` is [`Send`] if and only if `T` is [`Send`] +/// * `&T` and `&mut T` are [`Sync`] if and only if `T` is [`Sync`] +/// /// Types that are not `Sync` are those that have "interior /// mutability" in a non-thread-safe form, such as [`Cell`][cell] /// and [`RefCell`][refcell]. These types allow for mutation of @@ -591,14 +688,14 @@ impl<T: ?Sized> !Sync for *mut T {} /// use std::marker::PhantomData; /// /// # #[allow(dead_code)] -/// struct Slice<'a, T: 'a> { +/// struct Slice<'a, T> { /// start: *const T, /// end: *const T, /// phantom: PhantomData<&'a T>, /// } /// ``` /// -/// This also in turn requires the annotation `T: 'a`, indicating +/// This also in turn infers the lifetime bound `T: 'a`, indicating /// that any references in `T` are valid over the lifetime `'a`. /// /// When initializing a `Slice` you simply provide the value @@ -607,7 +704,7 @@ impl<T: ?Sized> !Sync for *mut T {} /// ``` /// # #![allow(dead_code)] /// # use std::marker::PhantomData; -/// # struct Slice<'a, T: 'a> { +/// # struct Slice<'a, T> { /// # start: *const T, /// # end: *const T, /// # phantom: PhantomData<&'a T>, @@ -669,16 +766,11 @@ impl<T: ?Sized> !Sync for *mut T {} /// /// ## Ownership and the drop check /// -/// Adding a field of type `PhantomData<T>` indicates that your -/// type owns data of type `T`. This in turn implies that when your -/// type is dropped, it may drop one or more instances of the type -/// `T`. This has bearing on the Rust compiler's [drop check] -/// analysis. +/// The exact interaction of `PhantomData` with drop check **may change in the future**. /// -/// If your struct does not in fact *own* the data of type `T`, it is -/// better to use a reference type, like `PhantomData<&'a T>` -/// (ideally) or `PhantomData<*const T>` (if no lifetime applies), so -/// as not to indicate ownership. +/// Currently, adding a field of type `PhantomData<T>` indicates that your type *owns* data of type +/// `T` in very rare circumstances. This in turn has effects on the Rust compiler's [drop check] +/// analysis. For the exact rules, see the [drop check] documentation. /// /// ## Layout /// @@ -686,7 +778,7 @@ impl<T: ?Sized> !Sync for *mut T {} /// * `size_of::<PhantomData<T>>() == 0` /// * `align_of::<PhantomData<T>>() == 1` /// -/// [drop check]: ../../nomicon/dropck.html +/// [drop check]: Drop#drop-check #[lang = "phantom_data"] #[stable(feature = "rust1", since = "1.0.0")] pub struct PhantomData<T: ?Sized>; @@ -773,11 +865,14 @@ pub trait DiscriminantKind { pub(crate) unsafe auto trait Freeze {} impl<T: ?Sized> !Freeze for UnsafeCell<T> {} -unsafe impl<T: ?Sized> Freeze for PhantomData<T> {} -unsafe impl<T: ?Sized> Freeze for *const T {} -unsafe impl<T: ?Sized> Freeze for *mut T {} -unsafe impl<T: ?Sized> Freeze for &T {} -unsafe impl<T: ?Sized> Freeze for &mut T {} +marker_impls! { + unsafe Freeze for + {T: ?Sized} PhantomData<T>, + {T: ?Sized} *const T, + {T: ?Sized} *mut T, + {T: ?Sized} &T, + {T: ?Sized} &mut T, +} /// Types that can be safely moved after being pinned. /// @@ -838,17 +933,19 @@ pub struct PhantomPinned; #[stable(feature = "pin", since = "1.33.0")] impl !Unpin for PhantomPinned {} -#[stable(feature = "pin", since = "1.33.0")] -impl<'a, T: ?Sized + 'a> Unpin for &'a T {} - -#[stable(feature = "pin", since = "1.33.0")] -impl<'a, T: ?Sized + 'a> Unpin for &'a mut T {} - -#[stable(feature = "pin_raw", since = "1.38.0")] -impl<T: ?Sized> Unpin for *const T {} +marker_impls! { + #[stable(feature = "pin", since = "1.33.0")] + Unpin for + {T: ?Sized} &T, + {T: ?Sized} &mut T, +} -#[stable(feature = "pin_raw", since = "1.38.0")] -impl<T: ?Sized> Unpin for *mut T {} +marker_impls! { + #[stable(feature = "pin_raw", since = "1.38.0")] + Unpin for + {T: ?Sized} *const T, + {T: ?Sized} *mut T, +} /// A marker for types that can be dropped. /// @@ -883,43 +980,25 @@ pub trait Tuple {} )] pub trait PointerLike {} -/// Implementations of `Copy` for primitive types. -/// -/// Implementations that cannot be described in Rust -/// are implemented in `traits::SelectionContext::copy_clone_conditions()` -/// in `rustc_trait_selection`. -mod copy_impls { - - use super::Copy; - - macro_rules! impl_copy { - ($($t:ty)*) => { - $( - #[stable(feature = "rust1", since = "1.0.0")] - impl Copy for $t {} - )* - } - } - - impl_copy! { - usize u8 u16 u32 u64 u128 - isize i8 i16 i32 i64 i128 - f32 f64 - bool char - } - - #[unstable(feature = "never_type", issue = "35121")] - impl Copy for ! {} - - #[stable(feature = "rust1", since = "1.0.0")] - impl<T: ?Sized> Copy for *const T {} - - #[stable(feature = "rust1", since = "1.0.0")] - impl<T: ?Sized> Copy for *mut T {} - - /// Shared references can be copied, but mutable references *cannot*! - #[stable(feature = "rust1", since = "1.0.0")] - impl<T: ?Sized> Copy for &T {} +/// A marker for types which can be used as types of `const` generic parameters. +#[cfg_attr(not(bootstrap), lang = "const_param_ty")] +#[unstable(feature = "adt_const_params", issue = "95174")] +#[rustc_on_unimplemented(message = "`{Self}` can't be used as a const parameter type")] +pub trait ConstParamTy: StructuralEq {} + +// FIXME(generic_const_parameter_types): handle `ty::FnDef`/`ty::Closure` +// FIXME(generic_const_parameter_types): handle `ty::Tuple` +marker_impls! { + #[unstable(feature = "adt_const_params", issue = "95174")] + ConstParamTy for + usize, u8, u16, u32, u64, u128, + isize, i8, i16, i32, i64, i128, + bool, + char, + str /* Technically requires `[u8]: ConstParamTy` */, + {T: ConstParamTy, const N: usize} [T; N], + {T: ConstParamTy} [T], + {T: ?Sized + ConstParamTy} &T, } /// A common trait implemented by all function pointers. |