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Enforce Tuple trait on Fn traits

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Michael Goulet 2022-07-30 01:53:53 +00:00
parent 6b8d9dd0a0
commit 2786acce98
4 changed files with 419 additions and 0 deletions
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31
library/alloc/src/boxed.rs
View file

@ -158,6 +158,8 @@
#[cfg(not(no_global_oom_handling))]
use core::iter::FromIterator;
use core::iter::{FusedIterator, Iterator};
#[cfg(not(bootstrap))]
use core::marker::Tuple;
use core::marker::{Destruct, Unpin, Unsize};
use core::mem;
use core::ops::{
@ -1979,6 +1981,7 @@ fn is_empty(&self) -> bool {
#[stable(feature = "fused", since = "1.26.0")]
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {}
#[cfg(bootstrap)]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
type Output = <F as FnOnce<Args>>::Output;
@ -1988,6 +1991,17 @@ extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
}
}
#[cfg(not(bootstrap))]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
type Output = <F as FnOnce<Args>>::Output;
extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
<F as FnOnce<Args>>::call_once(*self, args)
}
}
#[cfg(bootstrap)]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
@ -1995,6 +2009,15 @@ extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
}
}
#[cfg(not(bootstrap))]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args: Tuple, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
<F as FnMut<Args>>::call_mut(self, args)
}
}
#[cfg(bootstrap)]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
extern "rust-call" fn call(&self, args: Args) -> Self::Output {
@ -2002,6 +2025,14 @@ extern "rust-call" fn call(&self, args: Args) -> Self::Output {
}
}
#[cfg(not(bootstrap))]
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
impl<Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
extern "rust-call" fn call(&self, args: Args) -> Self::Output {
<F as Fn<Args>>::call(self, args)
}
}
#[unstable(feature = "coerce_unsized", issue = "27732")]
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}

1
library/alloc/src/lib.rs
View file

@ -150,6 +150,7 @@
#![feature(trusted_len)]
#![feature(trusted_random_access)]
#![feature(try_trait_v2)]
#![cfg_attr(not(bootstrap), feature(tuple_trait))]
#![feature(unchecked_math)]
#![feature(unicode_internals)]
#![feature(unsize)]

66
library/core/src/intrinsics.rs
View file

@ -55,6 +55,8 @@
#![allow(missing_docs)]
use crate::marker::DiscriminantKind;
#[cfg(not(bootstrap))]
use crate::marker::Tuple;
use crate::mem;
// These imports are used for simplifying intra-doc links
@ -2169,11 +2171,75 @@ pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
/// `unreachable_unchecked` is actually being reached. The bug is in *crate A*,
/// which violates the principle that a `const fn` must behave the same at
/// compile-time and at run-time. The unsafe code in crate B is fine.
#[cfg(bootstrap)]
#[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
pub fn const_eval_select<ARG, F, G, RET>(arg: ARG, called_in_const: F, called_at_rt: G) -> RET
where
G: FnOnce<ARG, Output = RET>,
F: FnOnce<ARG, Output = RET>;
/// Selects which function to call depending on the context.
///
/// If this function is evaluated at compile-time, then a call to this
/// intrinsic will be replaced with a call to `called_in_const`. It gets
/// replaced with a call to `called_at_rt` otherwise.
///
/// # Type Requirements
///
/// The two functions must be both function items. They cannot be function
/// pointers or closures. The first function must be a `const fn`.
///
/// `arg` will be the tupled arguments that will be passed to either one of
/// the two functions, therefore, both functions must accept the same type of
/// arguments. Both functions must return RET.
///
/// # Safety
///
/// The two functions must behave observably equivalent. Safe code in other
/// crates may assume that calling a `const fn` at compile-time and at run-time
/// produces the same result. A function that produces a different result when
/// evaluated at run-time, or has any other observable side-effects, is
/// *unsound*.
///
/// Here is an example of how this could cause a problem:
/// ```no_run
/// #![feature(const_eval_select)]
/// #![feature(core_intrinsics)]
/// use std::hint::unreachable_unchecked;
/// use std::intrinsics::const_eval_select;
///
/// // Crate A
/// pub const fn inconsistent() -> i32 {
/// fn runtime() -> i32 { 1 }
/// const fn compiletime() -> i32 { 2 }
///
/// unsafe {
// // ⚠ This code violates the required equivalence of `compiletime`
/// // and `runtime`.
/// const_eval_select((), compiletime, runtime)
/// }
/// }
///
/// // Crate B
/// const X: i32 = inconsistent();
/// let x = inconsistent();
/// if x != X { unsafe { unreachable_unchecked(); }}
/// ```
///
/// This code causes Undefined Behavior when being run, since the
/// `unreachable_unchecked` is actually being reached. The bug is in *crate A*,
/// which violates the principle that a `const fn` must behave the same at
/// compile-time and at run-time. The unsafe code in crate B is fine.
#[cfg(not(bootstrap))]
#[rustc_const_unstable(feature = "const_eval_select", issue = "none")]
pub fn const_eval_select<ARG: Tuple, F, G, RET>(
arg: ARG,
called_in_const: F,
called_at_rt: G,
) -> RET
where
G: FnOnce<ARG, Output = RET>,
F: FnOnce<ARG, Output = RET>;
}
// Some functions are defined here because they accidentally got made

321
library/core/src/ops/function.rs
View file

@ -1,3 +1,6 @@
#[cfg(not(bootstrap))]
use crate::marker::Tuple;
/// The version of the call operator that takes an immutable receiver.
///
/// Instances of `Fn` can be called repeatedly without mutating state.
@ -51,6 +54,7 @@
/// let double = |x| x * 2;
/// assert_eq!(call_with_one(double), 2);
/// ```
#[cfg(bootstrap)]
#[lang = "fn"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "Fn"]
@ -78,6 +82,87 @@ pub trait Fn<Args>: FnMut<Args> {
extern "rust-call" fn call(&self, args: Args) -> Self::Output;
}
/// The version of the call operator that takes an immutable receiver.
///
/// Instances of `Fn` can be called repeatedly without mutating state.
///
/// *This trait (`Fn`) is not to be confused with [function pointers]
/// (`fn`).*
///
/// `Fn` is implemented automatically by closures which only take immutable
/// references to captured variables or don't capture anything at all, as well
/// as (safe) [function pointers] (with some caveats, see their documentation
/// for more details). Additionally, for any type `F` that implements `Fn`, `&F`
/// implements `Fn`, too.
///
/// Since both [`FnMut`] and [`FnOnce`] are supertraits of `Fn`, any
/// instance of `Fn` can be used as a parameter where a [`FnMut`] or [`FnOnce`]
/// is expected.
///
/// Use `Fn` as a bound when you want to accept a parameter of function-like
/// type and need to call it repeatedly and without mutating state (e.g., when
/// calling it concurrently). If you do not need such strict requirements, use
/// [`FnMut`] or [`FnOnce`] as bounds.
///
/// See the [chapter on closures in *The Rust Programming Language*][book] for
/// some more information on this topic.
///
/// Also of note is the special syntax for `Fn` traits (e.g.
/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
///
/// [book]: ../../book/ch13-01-closures.html
/// [function pointers]: fn
/// [nomicon]: ../../nomicon/hrtb.html
///
/// # Examples
///
/// ## Calling a closure
///
/// ```
/// let square = |x| x * x;
/// assert_eq!(square(5), 25);
/// ```
///
/// ## Using a `Fn` parameter
///
/// ```
/// fn call_with_one<F>(func: F) -> usize
/// where F: Fn(usize) -> usize {
/// func(1)
/// }
///
/// let double = |x| x * 2;
/// assert_eq!(call_with_one(double), 2);
/// ```
#[cfg(not(bootstrap))]
#[lang = "fn"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "Fn"]
#[rustc_paren_sugar]
#[rustc_on_unimplemented(
on(
Args = "()",
note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
),
on(
_Self = "unsafe fn",
note = "unsafe function cannot be called generically without an unsafe block",
// SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
),
message = "expected a `{Fn}<{Args}>` closure, found `{Self}`",
label = "expected an `Fn<{Args}>` closure, found `{Self}`"
)]
#[fundamental] // so that regex can rely that `&str: !FnMut`
#[must_use = "closures are lazy and do nothing unless called"]
#[const_trait]
pub trait Fn<Args: Tuple>: FnMut<Args> {
/// Performs the call operation.
#[unstable(feature = "fn_traits", issue = "29625")]
extern "rust-call" fn call(&self, args: Args) -> Self::Output;
}
/// The version of the call operator that takes a mutable receiver.
///
/// Instances of `FnMut` can be called repeatedly and may mutate state.
@ -139,6 +224,7 @@ pub trait Fn<Args>: FnMut<Args> {
///
/// assert_eq!(x, 5);
/// ```
#[cfg(bootstrap)]
#[lang = "fn_mut"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "FnMut"]
@ -166,6 +252,95 @@ pub trait FnMut<Args>: FnOnce<Args> {
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output;
}
/// The version of the call operator that takes a mutable receiver.
///
/// Instances of `FnMut` can be called repeatedly and may mutate state.
///
/// `FnMut` is implemented automatically by closures which take mutable
/// references to captured variables, as well as all types that implement
/// [`Fn`], e.g., (safe) [function pointers] (since `FnMut` is a supertrait of
/// [`Fn`]). Additionally, for any type `F` that implements `FnMut`, `&mut F`
/// implements `FnMut`, too.
///
/// Since [`FnOnce`] is a supertrait of `FnMut`, any instance of `FnMut` can be
/// used where a [`FnOnce`] is expected, and since [`Fn`] is a subtrait of
/// `FnMut`, any instance of [`Fn`] can be used where `FnMut` is expected.
///
/// Use `FnMut` as a bound when you want to accept a parameter of function-like
/// type and need to call it repeatedly, while allowing it to mutate state.
/// If you don't want the parameter to mutate state, use [`Fn`] as a
/// bound; if you don't need to call it repeatedly, use [`FnOnce`].
///
/// See the [chapter on closures in *The Rust Programming Language*][book] for
/// some more information on this topic.
///
/// Also of note is the special syntax for `Fn` traits (e.g.
/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
///
/// [book]: ../../book/ch13-01-closures.html
/// [function pointers]: fn
/// [nomicon]: ../../nomicon/hrtb.html
///
/// # Examples
///
/// ## Calling a mutably capturing closure
///
/// ```
/// let mut x = 5;
/// {
/// let mut square_x = || x *= x;
/// square_x();
/// }
/// assert_eq!(x, 25);
/// ```
///
/// ## Using a `FnMut` parameter
///
/// ```
/// fn do_twice<F>(mut func: F)
/// where F: FnMut()
/// {
/// func();
/// func();
/// }
///
/// let mut x: usize = 1;
/// {
/// let add_two_to_x = || x += 2;
/// do_twice(add_two_to_x);
/// }
///
/// assert_eq!(x, 5);
/// ```
#[cfg(not(bootstrap))]
#[lang = "fn_mut"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "FnMut"]
#[rustc_paren_sugar]
#[rustc_on_unimplemented(
on(
Args = "()",
note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
),
on(
_Self = "unsafe fn",
note = "unsafe function cannot be called generically without an unsafe block",
// SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
),
message = "expected a `{FnMut}<{Args}>` closure, found `{Self}`",
label = "expected an `FnMut<{Args}>` closure, found `{Self}`"
)]
#[fundamental] // so that regex can rely that `&str: !FnMut`
#[must_use = "closures are lazy and do nothing unless called"]
#[const_trait]
pub trait FnMut<Args: Tuple>: FnOnce<Args> {
/// Performs the call operation.
#[unstable(feature = "fn_traits", issue = "29625")]
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output;
}
/// The version of the call operator that takes a by-value receiver.
///
/// Instances of `FnOnce` can be called, but might not be callable multiple
@ -219,6 +394,7 @@ pub trait FnMut<Args>: FnOnce<Args> {
///
/// // `consume_and_return_x` can no longer be invoked at this point
/// ```
#[cfg(bootstrap)]
#[lang = "fn_once"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "FnOnce"]
@ -251,6 +427,93 @@ pub trait FnOnce<Args> {
extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
}
/// The version of the call operator that takes a by-value receiver.
///
/// Instances of `FnOnce` can be called, but might not be callable multiple
/// times. Because of this, if the only thing known about a type is that it
/// implements `FnOnce`, it can only be called once.
///
/// `FnOnce` is implemented automatically by closures that might consume captured
/// variables, as well as all types that implement [`FnMut`], e.g., (safe)
/// [function pointers] (since `FnOnce` is a supertrait of [`FnMut`]).
///
/// Since both [`Fn`] and [`FnMut`] are subtraits of `FnOnce`, any instance of
/// [`Fn`] or [`FnMut`] can be used where a `FnOnce` is expected.
///
/// Use `FnOnce` as a bound when you want to accept a parameter of function-like
/// type and only need to call it once. If you need to call the parameter
/// repeatedly, use [`FnMut`] as a bound; if you also need it to not mutate
/// state, use [`Fn`].
///
/// See the [chapter on closures in *The Rust Programming Language*][book] for
/// some more information on this topic.
///
/// Also of note is the special syntax for `Fn` traits (e.g.
/// `Fn(usize, bool) -> usize`). Those interested in the technical details of
/// this can refer to [the relevant section in the *Rustonomicon*][nomicon].
///
/// [book]: ../../book/ch13-01-closures.html
/// [function pointers]: fn
/// [nomicon]: ../../nomicon/hrtb.html
///
/// # Examples
///
/// ## Using a `FnOnce` parameter
///
/// ```
/// fn consume_with_relish<F>(func: F)
/// where F: FnOnce() -> String
/// {
/// // `func` consumes its captured variables, so it cannot be run more
/// // than once.
/// println!("Consumed: {}", func());
///
/// println!("Delicious!");
///
/// // Attempting to invoke `func()` again will throw a `use of moved
/// // value` error for `func`.
/// }
///
/// let x = String::from("x");
/// let consume_and_return_x = move || x;
/// consume_with_relish(consume_and_return_x);
///
/// // `consume_and_return_x` can no longer be invoked at this point
/// ```
#[cfg(not(bootstrap))]
#[lang = "fn_once"]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_diagnostic_item = "FnOnce"]
#[rustc_paren_sugar]
#[rustc_on_unimplemented(
on(
Args = "()",
note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
),
on(
_Self = "unsafe fn",
note = "unsafe function cannot be called generically without an unsafe block",
// SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
),
message = "expected a `{FnOnce}<{Args}>` closure, found `{Self}`",
label = "expected an `FnOnce<{Args}>` closure, found `{Self}`"
)]
#[fundamental] // so that regex can rely that `&str: !FnMut`
#[must_use = "closures are lazy and do nothing unless called"]
#[const_trait]
pub trait FnOnce<Args: Tuple> {
/// The returned type after the call operator is used.
#[lang = "fn_once_output"]
#[stable(feature = "fn_once_output", since = "1.12.0")]
type Output;
/// Performs the call operation.
#[unstable(feature = "fn_traits", issue = "29625")]
extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
}
#[cfg(bootstrap)]
mod impls {
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_fn_trait_ref_impls", issue = "101803")]
@ -310,3 +573,61 @@ extern "rust-call" fn call_once(self, args: A) -> F::Output {
}
}
}
#[cfg(not(bootstrap))]
mod impls {
use crate::marker::Tuple;
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Tuple, F: ?Sized> Fn<A> for &F
where
F: Fn<A>,
{
extern "rust-call" fn call(&self, args: A) -> F::Output {
(**self).call(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Tuple, F: ?Sized> FnMut<A> for &F
where
F: Fn<A>,
{
extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
(**self).call(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Tuple, F: ?Sized> FnOnce<A> for &F
where
F: Fn<A>,
{
type Output = F::Output;
extern "rust-call" fn call_once(self, args: A) -> F::Output {
(*self).call(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Tuple, F: ?Sized> FnMut<A> for &mut F
where
F: FnMut<A>,
{
extern "rust-call" fn call_mut(&mut self, args: A) -> F::Output {
(*self).call_mut(args)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<A: Tuple, F: ?Sized> FnOnce<A> for &mut F
where
F: FnMut<A>,
{
type Output = F::Output;
extern "rust-call" fn call_once(self, args: A) -> F::Output {
(*self).call_mut(args)
}
}
}