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Aug 3, 2025
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Constify some more Result functions #143771

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137 changes: 112 additions & 25 deletions library/core/src/result.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -534,6 +534,7 @@
#![stable(feature = "rust1", since = "1.0.0")]

use crate::iter::{self, FusedIterator, TrustedLen};
use crate::marker::Destruct;
use crate::ops::{self, ControlFlow, Deref, DerefMut};
use crate::{convert, fmt, hint};

Expand Down Expand Up @@ -606,7 +607,13 @@ impl<T, E> Result<T, E> {
#[must_use]
#[inline]
#[stable(feature = "is_some_and", since = "1.70.0")]
pub fn is_ok_and(self, f: impl FnOnce(T) -> bool) -> bool {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn is_ok_and<F>(self, f: F) -> bool
where
F: ~const FnOnce(T) -> bool + ~const Destruct,
T: ~const Destruct,
E: ~const Destruct,
{
match self {
Err(_) => false,
Ok(x) => f(x),
Expand Down Expand Up @@ -655,7 +662,13 @@ impl<T, E> Result<T, E> {
#[must_use]
#[inline]
#[stable(feature = "is_some_and", since = "1.70.0")]
pub fn is_err_and(self, f: impl FnOnce(E) -> bool) -> bool {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn is_err_and<F>(self, f: F) -> bool
where
F: ~const FnOnce(E) -> bool + ~const Destruct,
E: ~const Destruct,
T: ~const Destruct,
{
match self {
Ok(_) => false,
Err(e) => f(e),
Expand All @@ -682,8 +695,13 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
#[rustc_diagnostic_item = "result_ok_method"]
pub fn ok(self) -> Option<T> {
pub const fn ok(self) -> Option<T>
where
T: ~const Destruct,
E: ~const Destruct,
{
match self {
Ok(x) => Some(x),
Err(_) => None,
Expand All @@ -706,7 +724,12 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn err(self) -> Option<E> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn err(self) -> Option<E>
where
T: ~const Destruct,
E: ~const Destruct,
{
match self {
Ok(_) => None,
Err(x) => Some(x),
Expand Down Expand Up @@ -796,7 +819,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn map<U, F: FnOnce(T) -> U>(self, op: F) -> Result<U, E> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn map<U, F>(self, op: F) -> Result<U, E>
where
F: ~const FnOnce(T) -> U + ~const Destruct,
{
match self {
Ok(t) => Ok(op(t)),
Err(e) => Err(e),
Expand All @@ -823,8 +850,15 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "result_map_or", since = "1.41.0")]
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
#[must_use = "if you don't need the returned value, use `if let` instead"]
pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U {
pub const fn map_or<U, F>(self, default: U, f: F) -> U
where
F: ~const FnOnce(T) -> U + ~const Destruct,
T: ~const Destruct,
E: ~const Destruct,
U: ~const Destruct,
{
match self {
Ok(t) => f(t),
Err(_) => default,
Expand All @@ -851,7 +885,12 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "result_map_or_else", since = "1.41.0")]
pub fn map_or_else<U, D: FnOnce(E) -> U, F: FnOnce(T) -> U>(self, default: D, f: F) -> U {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn map_or_else<U, D, F>(self, default: D, f: F) -> U
where
D: ~const FnOnce(E) -> U + ~const Destruct,
F: ~const FnOnce(T) -> U + ~const Destruct,
{
match self {
Ok(t) => f(t),
Err(e) => default(e),
Expand All @@ -877,10 +916,13 @@ impl<T, E> Result<T, E> {
/// [default value]: Default::default
#[inline]
#[unstable(feature = "result_option_map_or_default", issue = "138099")]
pub fn map_or_default<U, F>(self, f: F) -> U
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn map_or_default<U, F>(self, f: F) -> U
where
U: Default,
F: FnOnce(T) -> U,
F: ~const FnOnce(T) -> U + ~const Destruct,
U: ~const Default,
T: ~const Destruct,
E: ~const Destruct,
{
match self {
Ok(t) => f(t),
Expand Down Expand Up @@ -908,7 +950,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn map_err<F, O: FnOnce(E) -> F>(self, op: O) -> Result<T, F> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn map_err<F, O>(self, op: O) -> Result<T, F>
where
O: ~const FnOnce(E) -> F + ~const Destruct,
{
match self {
Ok(t) => Ok(t),
Err(e) => Err(op(e)),
Expand All @@ -930,7 +976,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "result_option_inspect", since = "1.76.0")]
pub fn inspect<F: FnOnce(&T)>(self, f: F) -> Self {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn inspect<F>(self, f: F) -> Self
where
F: ~const FnOnce(&T) + ~const Destruct,
{
if let Ok(ref t) = self {
f(t);
}
Expand All @@ -954,7 +1004,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "result_option_inspect", since = "1.76.0")]
pub fn inspect_err<F: FnOnce(&E)>(self, f: F) -> Self {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn inspect_err<F>(self, f: F) -> Self
where
F: ~const FnOnce(&E) + ~const Destruct,
{
if let Err(ref e) = self {
f(e);
}
Expand Down Expand Up @@ -1033,7 +1087,8 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter(&self) -> Iter<'_, T> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn iter(&self) -> Iter<'_, T> {
Iter { inner: self.as_ref().ok() }
}

Expand All @@ -1056,7 +1111,8 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn iter_mut(&mut self) -> IterMut<'_, T> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn iter_mut(&mut self) -> IterMut<'_, T> {
IterMut { inner: self.as_mut().ok() }
}

Expand Down Expand Up @@ -1195,9 +1251,11 @@ impl<T, E> Result<T, E> {
/// [`FromStr`]: crate::str::FromStr
#[inline]
#[stable(feature = "result_unwrap_or_default", since = "1.16.0")]
pub fn unwrap_or_default(self) -> T
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn unwrap_or_default(self) -> T
where
T: Default,
T: ~const Default + ~const Destruct,
E: ~const Destruct,
{
match self {
Ok(x) => x,
Expand Down Expand Up @@ -1370,7 +1428,13 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn and<U>(self, res: Result<U, E>) -> Result<U, E> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn and<U>(self, res: Result<U, E>) -> Result<U, E>
where
T: ~const Destruct,
E: ~const Destruct,
U: ~const Destruct,
{
match self {
Ok(_) => res,
Err(e) => Err(e),
Expand Down Expand Up @@ -1409,8 +1473,12 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
#[rustc_confusables("flat_map", "flatmap")]
pub fn and_then<U, F: FnOnce(T) -> Result<U, E>>(self, op: F) -> Result<U, E> {
pub const fn and_then<U, F>(self, op: F) -> Result<U, E>
where
F: ~const FnOnce(T) -> Result<U, E> + ~const Destruct,
{
match self {
Ok(t) => op(t),
Err(e) => Err(e),
Expand Down Expand Up @@ -1446,7 +1514,13 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn or<F>(self, res: Result<T, F>) -> Result<T, F> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn or<F>(self, res: Result<T, F>) -> Result<T, F>
where
T: ~const Destruct,
E: ~const Destruct,
F: ~const Destruct,
{
match self {
Ok(v) => Ok(v),
Err(_) => res,
Expand All @@ -1471,7 +1545,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn or_else<F, O>(self, op: O) -> Result<T, F>
where
O: ~const FnOnce(E) -> Result<T, F> + ~const Destruct,
{
match self {
Ok(t) => Ok(t),
Err(e) => op(e),
Expand All @@ -1498,7 +1576,12 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn unwrap_or(self, default: T) -> T {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn unwrap_or(self, default: T) -> T
where
T: ~const Destruct,
E: ~const Destruct,
{
match self {
Ok(t) => t,
Err(_) => default,
Expand All @@ -1519,7 +1602,11 @@ impl<T, E> Result<T, E> {
#[inline]
#[track_caller]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn unwrap_or_else<F: FnOnce(E) -> T>(self, op: F) -> T {
#[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
pub const fn unwrap_or_else<F>(self, op: F) -> T
where
F: ~const FnOnce(E) -> T + ~const Destruct,
{
match self {
Ok(t) => t,
Err(e) => op(e),
Expand Down Expand Up @@ -1762,7 +1849,7 @@ impl<T, E> Result<Result<T, E>, E> {
#[cold]
#[track_caller]
fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
panic!("{msg}: {error:?}")
panic!("{msg}: {error:?}");
}

// This is a separate function to avoid constructing a `dyn Debug`
Expand All @@ -1773,7 +1860,7 @@ fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
#[inline]
#[cold]
#[track_caller]
fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
const fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
panic!()
}

Expand Down
2 changes: 2 additions & 0 deletions library/coretests/tests/lib.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#![feature(const_eval_select)]
#![feature(const_ops)]
#![feature(const_ref_cell)]
#![feature(const_result_trait_fn)]
#![feature(const_trait_impl)]
#![feature(core_float_math)]
#![feature(core_intrinsics)]
Expand Down Expand Up @@ -82,6 +83,7 @@
#![feature(pointer_is_aligned_to)]
#![feature(portable_simd)]
#![feature(ptr_metadata)]
#![feature(result_option_map_or_default)]
#![feature(slice_from_ptr_range)]
#![feature(slice_internals)]
#![feature(slice_partition_dedup)]
Expand Down
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