diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs index a3e91bc0670..df32c83f645 100644 --- a/library/core/src/cell.rs +++ b/library/core/src/cell.rs @@ -661,7 +661,7 @@ pub fn take(&self) -> T { impl, U> CoerceUnsized> for Cell {} // Allow types that wrap `Cell` to also implement `DispatchFromDyn` -// and become object safe method receivers. +// and become dyn-compatible method receivers. // Note that currently `Cell` itself cannot be a method receiver // because it does not implement Deref. // In other words: @@ -2236,7 +2236,7 @@ fn from(t: T) -> UnsafeCell { impl, U> CoerceUnsized> for UnsafeCell {} // Allow types that wrap `UnsafeCell` to also implement `DispatchFromDyn` -// and become object safe method receivers. +// and become dyn-compatible method receivers. // Note that currently `UnsafeCell` itself cannot be a method receiver // because it does not implement Deref. // In other words: @@ -2379,7 +2379,7 @@ fn from(t: T) -> SyncUnsafeCell { impl, U> CoerceUnsized> for SyncUnsafeCell {} // Allow types that wrap `SyncUnsafeCell` to also implement `DispatchFromDyn` -// and become object safe method receivers. +// and become dyn-compatible method receivers. // Note that currently `SyncUnsafeCell` itself cannot be a method receiver // because it does not implement Deref. // In other words: diff --git a/library/core/src/error.rs b/library/core/src/error.rs index cac00b37d1f..95a39cc3aed 100644 --- a/library/core/src/error.rs +++ b/library/core/src/error.rs @@ -335,16 +335,17 @@ impl dyn Error { #[unstable(feature = "error_iter", issue = "58520")] #[inline] pub fn sources(&self) -> Source<'_> { - // You may think this method would be better in the Error trait, and you'd be right. - // Unfortunately that doesn't work, not because of the object safety rules but because we - // save a reference to self in Sources below as a trait object. If this method was - // declared in Error, then self would have the type &T where T is some concrete type which - // implements Error. We would need to coerce self to have type &dyn Error, but that requires - // that Self has a known size (i.e., Self: Sized). We can't put that bound on Error - // since that would forbid Error trait objects, and we can't put that bound on the method - // because that means the method can't be called on trait objects (we'd also need the - // 'static bound, but that isn't allowed because methods with bounds on Self other than - // Sized are not object-safe). Requiring an Unsize bound is not backwards compatible. + // You may think this method would be better in the `Error` trait, and you'd be right. + // Unfortunately that doesn't work, not because of the dyn-incompatibility rules but + // because we save a reference to `self` in `Source`s below as a trait object. + // If this method was declared in `Error`, then `self` would have the type `&T` where + // `T` is some concrete type which implements `Error`. We would need to coerce `self` + // to have type `&dyn Error`, but that requires that `Self` has a known size + // (i.e., `Self: Sized`). We can't put that bound on `Error` since that would forbid + // `Error` trait objects, and we can't put that bound on the method because that means + // the method can't be called on trait objects (we'd also need the `'static` bound, + // but that isn't allowed because methods with bounds on `Self` other than `Sized` are + // dyn-incompatible). Requiring an `Unsize` bound is not backwards compatible. Source { current: Some(self) } } diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs index 7963459bfb5..302720eddef 100644 --- a/library/core/src/iter/traits/iterator.rs +++ b/library/core/src/iter/traits/iterator.rs @@ -9,7 +9,7 @@ use crate::num::NonZero; use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, Residual, Try}; -fn _assert_is_object_safe(_: &dyn Iterator) {} +fn _assert_is_dyn_compatible(_: &dyn Iterator) {} /// A trait for dealing with iterators. /// diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs index fd41b80cdbd..aed6be4c627 100644 --- a/library/core/src/marker.rs +++ b/library/core/src/marker.rs @@ -158,7 +158,7 @@ pub trait Sized { /// - Arrays `[T; N]` implement `Unsize<[T]>`. /// - A type implements `Unsize` if all of these conditions are met: /// - The type implements `Trait`. -/// - `Trait` is object safe. +/// - `Trait` is dyn-compatible[^1]. /// - The type is sized. /// - The type outlives `'a`. /// - Structs `Foo<..., T1, ..., Tn, ...>` implement `Unsize>` @@ -178,6 +178,7 @@ pub trait Sized { /// [`Rc`]: ../../std/rc/struct.Rc.html /// [RFC982]: https://github.com/rust-lang/rfcs/blob/master/text/0982-dst-coercion.md /// [nomicon-coerce]: ../../nomicon/coercions.html +/// [^1]: Formerly known as *object safe*. #[unstable(feature = "unsize", issue = "18598")] #[lang = "unsize"] #[rustc_deny_explicit_impl(implement_via_object = false)] diff --git a/library/core/src/ops/unsize.rs b/library/core/src/ops/unsize.rs index b51f12580ea..d2a07197f6f 100644 --- a/library/core/src/ops/unsize.rs +++ b/library/core/src/ops/unsize.rs @@ -68,8 +68,8 @@ impl, U: ?Sized> CoerceUnsized<*const U> for *mut T {} #[unstable(feature = "coerce_unsized", issue = "18598")] impl, U: ?Sized> CoerceUnsized<*const U> for *const T {} -/// `DispatchFromDyn` is used in the implementation of object safety checks (specifically allowing -/// arbitrary self types), to guarantee that a method's receiver type can be dispatched on. +/// `DispatchFromDyn` is used in the implementation of dyn-compatibility[^1] checks (specifically +/// allowing arbitrary self types), to guarantee that a method's receiver type can be dispatched on. /// /// Note: `DispatchFromDyn` was briefly named `CoerceSized` (and had a slightly different /// interpretation). @@ -80,7 +80,7 @@ impl, U: ?Sized> CoerceUnsized<*const U> for *const T {} /// type). The compiler must generate an implicit conversion from the trait object/wide pointer to /// the concrete reference/narrow pointer. Implementing `DispatchFromDyn` indicates that that /// conversion is allowed and thus that the type implementing `DispatchFromDyn` is safe to use as -/// the self type in an object-safe method. (in the above example, the compiler will require +/// the self type in an dyn-compatible method. (in the above example, the compiler will require /// `DispatchFromDyn` is implemented for `&'a U`). /// /// `DispatchFromDyn` does not specify the conversion from wide pointer to narrow pointer; the @@ -112,6 +112,8 @@ impl, U: ?Sized> CoerceUnsized<*const U> for *const T {} /// T: Unsize, /// {} /// ``` +/// +/// [^1]: Formerly known as *object safety*. #[unstable(feature = "dispatch_from_dyn", issue = "none")] #[lang = "dispatch_from_dyn"] pub trait DispatchFromDyn { diff --git a/library/core/tests/hash/mod.rs b/library/core/tests/hash/mod.rs index 03826fc4c92..bf91e9e5df0 100644 --- a/library/core/tests/hash/mod.rs +++ b/library/core/tests/hash/mod.rs @@ -164,7 +164,7 @@ fn test_indirect_hasher() { } #[test] -fn test_build_hasher_object_safe() { +fn test_build_hasher_dyn_compatible() { use std::hash::{DefaultHasher, RandomState}; let _: &dyn BuildHasher = &RandomState::new(); diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs index 9f4d244b547..453b2708daa 100644 --- a/library/std/src/keyword_docs.rs +++ b/library/std/src/keyword_docs.rs @@ -2349,12 +2349,13 @@ mod async_keyword {} /// [`async`]: ../std/keyword.async.html mod await_keyword {} +// FIXME(dyn_compat_renaming): Update URL and link text. #[doc(keyword = "dyn")] // /// `dyn` is a prefix of a [trait object]'s type. /// /// The `dyn` keyword is used to highlight that calls to methods on the associated `Trait` -/// are [dynamically dispatched]. To use the trait this way, it must be 'object safe'. +/// are [dynamically dispatched]. To use the trait this way, it must be 'dyn-compatible'[^1]. /// /// Unlike generic parameters or `impl Trait`, the compiler does not know the concrete type that /// is being passed. That is, the type has been [erased]. @@ -2382,6 +2383,7 @@ mod await_keyword {} /// [ref-trait-obj]: ../reference/types/trait-object.html /// [ref-obj-safety]: ../reference/items/traits.html#object-safety /// [erased]: https://en.wikipedia.org/wiki/Type_erasure +/// [^1]: Formerly known as 'object safe'. mod dyn_keyword {} #[doc(keyword = "union")]