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Make more Result methods const #104407

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1 change: 1 addition & 0 deletions library/core/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -128,6 +128,7 @@
#![feature(const_ops)]
#![feature(const_option)]
#![feature(const_option_ext)]
#![feature(const_result)]
#![feature(const_pin)]
#![feature(const_ptr_sub_ptr)]
#![feature(const_replace)]
Expand Down
128 changes: 101 additions & 27 deletions library/core/src/result.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -770,7 +770,11 @@ 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", issue = "82814")]
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 @@ -797,7 +801,14 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "result_map_or", since = "1.41.0")]
pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U {
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn map_or<U, F>(self, default: U, f: F) -> U
where
T: ~const Destruct,
E: ~const Destruct,
U: ~const Destruct,
F: ~const FnOnce(T) -> U + ~const Destruct,
{
match self {
Ok(t) => f(t),
Err(_) => default,
Expand Down Expand Up @@ -826,7 +837,12 @@ 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", issue = "82814")]
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 Down Expand Up @@ -855,7 +871,11 @@ 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", issue = "82814")]
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 Down Expand Up @@ -926,11 +946,17 @@ impl<T, E> Result<T, E> {
/// assert_eq!(x.as_deref(), y);
/// ```
#[stable(feature = "inner_deref", since = "1.47.0")]
pub fn as_deref(&self) -> Result<&T::Target, &E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn as_deref(&self) -> Result<&T::Target, &E>
where
T: Deref,
T: ~const Deref,
{
self.as_ref().map(|t| t.deref())
// FIXME (#104314): `self.as_ref().map(Deref::deref)` is rejected
// because `Deref::deref` does not impl `~const FnOnce`
match self.as_ref() {
Ok(t) => Ok(t.deref()),
Err(e) => Err(e),
}
}

/// Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`.
Expand All @@ -952,11 +978,17 @@ impl<T, E> Result<T, E> {
/// assert_eq!(x.as_deref_mut().map(|x| { x.make_ascii_uppercase(); x }), y);
/// ```
#[stable(feature = "inner_deref", since = "1.47.0")]
pub fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn as_deref_mut(&mut self) -> Result<&mut T::Target, &mut E>
where
T: DerefMut,
T: ~const DerefMut,
{
self.as_mut().map(|t| t.deref_mut())
// FIXME (#104314): `self.as_mut().map(DerefMut::deref_mut)` is rejected
// because `DerefMut::deref_mut` does not impl `~const FnOnce`
match self.as_mut() {
Ok(t) => Ok(t.deref_mut()),
Err(e) => Err(e),
}
}

/////////////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -1141,9 +1173,11 @@ 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", issue = "82814")]
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 @@ -1367,7 +1401,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn and_then<U, F: FnOnce(T) -> Result<U, E>>(self, op: F) -> Result<U, E> {
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
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 @@ -1440,7 +1478,11 @@ 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", issue = "82814")]
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 Down Expand Up @@ -1498,7 +1540,11 @@ impl<T, E> Result<T, E> {
/// ```
#[inline]
#[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", issue = "82814")]
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 @@ -1528,7 +1574,12 @@ impl<T, E> Result<T, E> {
#[inline]
#[track_caller]
#[stable(feature = "option_result_unwrap_unchecked", since = "1.58.0")]
pub unsafe fn unwrap_unchecked(self) -> T {
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const unsafe fn unwrap_unchecked(self) -> T
where
T: ~const Destruct,
E: ~const Destruct,
{
debug_assert!(self.is_ok());
match self {
Ok(t) => t,
Expand Down Expand Up @@ -1560,7 +1611,12 @@ impl<T, E> Result<T, E> {
#[inline]
#[track_caller]
#[stable(feature = "option_result_unwrap_unchecked", since = "1.58.0")]
pub unsafe fn unwrap_err_unchecked(self) -> E {
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const unsafe fn unwrap_err_unchecked(self) -> E
where
T: ~const Destruct,
E: ~const Destruct,
{
debug_assert!(self.is_err());
match self {
// SAFETY: the safety contract must be upheld by the caller.
Expand Down Expand Up @@ -1647,11 +1703,15 @@ impl<T, E> Result<&T, E> {
/// ```
#[inline]
#[stable(feature = "result_copied", since = "1.59.0")]
pub fn copied(self) -> Result<T, E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn copied(self) -> Result<T, E>
where
T: Copy,
{
self.map(|&t| t)
match self {
Ok(&t) => Ok(t),
Err(e) => Err(e),
}
}

/// Maps a `Result<&T, E>` to a `Result<T, E>` by cloning the contents of the
Expand All @@ -1668,11 +1728,17 @@ impl<T, E> Result<&T, E> {
/// ```
#[inline]
#[stable(feature = "result_cloned", since = "1.59.0")]
pub fn cloned(self) -> Result<T, E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn cloned(self) -> Result<T, E>
where
T: Clone,
T: ~const Clone,
{
self.map(|t| t.clone())
// FIXME (#104314): `self.map(Clone::clone)` is rejected
// because `Clone::clone` does not impl `~const FnOnce`
match self {
Ok(t) => Ok(t.clone()),
Err(e) => Err(e),
}
}
}

Expand All @@ -1691,11 +1757,15 @@ impl<T, E> Result<&mut T, E> {
/// ```
#[inline]
#[stable(feature = "result_copied", since = "1.59.0")]
pub fn copied(self) -> Result<T, E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn copied(self) -> Result<T, E>
where
T: Copy,
{
self.map(|&mut t| t)
match self {
Ok(&mut t) => Ok(t),
Err(e) => Err(e),
}
}

/// Maps a `Result<&mut T, E>` to a `Result<T, E>` by cloning the contents of the
Expand All @@ -1712,11 +1782,15 @@ impl<T, E> Result<&mut T, E> {
/// ```
#[inline]
#[stable(feature = "result_cloned", since = "1.59.0")]
pub fn cloned(self) -> Result<T, E>
#[rustc_const_unstable(feature = "const_result", issue = "82814")]
pub const fn cloned(self) -> Result<T, E>
where
T: Clone,
T: ~const Clone,
{
self.map(|t| t.clone())
match self {
Ok(t) => Ok(t.clone()),
Err(e) => Err(e),
}
}
}

Expand Down