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Rollup merge of #92385 - clarfonthey:const_option, r=fee1-dead

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Add Result::{ok, err, and, or, unwrap_or} as const

Already opened tracking issue #92384.

I don't think that this should actually cause any issues as long as the constness is unstable, but we may want to double-check that this doesn't get interpreted as a weird `Drop` bound even for non-const usages.
This commit is contained in:
Matthias Krüger 2022-03-08 11:04:50 +01:00 committed by GitHub
commit e22331ce02
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1 changed files with 45 additions and 10 deletions
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55
library/core/src/result.rs
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@ -632,10 +632,16 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn ok(self) -> Option<T> {
#[rustc_const_unstable(feature = "const_result_drop", issue = "92384")]
pub const fn ok(self) -> Option<T>
where
E: ~const Drop,
{
match self {
Ok(x) => Some(x),
Err(_) => None,
// FIXME: ~const Drop doesn't quite work right yet
#[allow(unused_variables)]
Err(x) => None,
}
}
@ -657,9 +663,15 @@ 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_drop", issue = "92384")]
pub const fn err(self) -> Option<E>
where
T: ~const Drop,
{
match self {
Ok(_) => None,
// FIXME: ~const Drop doesn't quite work right yet
#[allow(unused_variables)]
Ok(x) => None,
Err(x) => Some(x),
}
}
@ -1266,10 +1278,18 @@ impl<T, E> Result<T, E> {
/// assert_eq!(x.and(y), Ok("different result type"));
/// ```
#[inline]
#[rustc_const_unstable(feature = "const_result_drop", issue = "92384")]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn and<U>(self, res: Result<U, E>) -> Result<U, E> {
pub const fn and<U>(self, res: Result<U, E>) -> Result<U, E>
where
T: ~const Drop,
U: ~const Drop,
E: ~const Drop,
{
match self {
Ok(_) => res,
// FIXME: ~const Drop doesn't quite work right yet
#[allow(unused_variables)]
Ok(x) => res,
Err(e) => Err(e),
}
}
@ -1343,11 +1363,19 @@ impl<T, E> Result<T, E> {
/// assert_eq!(x.or(y), Ok(2));
/// ```
#[inline]
#[rustc_const_unstable(feature = "const_result_drop", issue = "92384")]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn or<F>(self, res: Result<T, F>) -> Result<T, F> {
pub const fn or<F>(self, res: Result<T, F>) -> Result<T, F>
where
T: ~const Drop,
E: ~const Drop,
F: ~const Drop,
{
match self {
Ok(v) => Ok(v),
Err(_) => res,
// FIXME: ~const Drop doesn't quite work right yet
#[allow(unused_variables)]
Err(e) => res,
}
}
@ -1399,11 +1427,18 @@ impl<T, E> Result<T, E> {
/// assert_eq!(x.unwrap_or(default), default);
/// ```
#[inline]
#[rustc_const_unstable(feature = "const_result_drop", issue = "92384")]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn unwrap_or(self, default: T) -> T {
pub const fn unwrap_or(self, default: T) -> T
where
T: ~const Drop,
E: ~const Drop,
{
match self {
Ok(t) => t,
Err(_) => default,
// FIXME: ~const Drop doesn't quite work right yet
#[allow(unused_variables)]
Err(e) => default,
}
}