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Constify ControlFlow methods with unstable bounds #148285

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Merged
merged 2 commits into from
Nov 10, 2025
Merged

Constify ControlFlow methods with unstable bounds #148285

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852bd86
Constify `ControlFlow` methods (unstable bounds)
nxsaken Oct 30, 2025
3175799
Add tracking issue number
nxsaken Nov 9, 2025
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25 changes: 21 additions & 4 deletions library/core/src/ops/control_flow.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
use crate::marker::Destruct;
use crate::{convert, ops};

/// Used to tell an operation whether it should exit early or go on as usual.
Expand Down Expand Up @@ -183,7 +184,11 @@ impl<B, C> ControlFlow<B, C> {
/// ```
#[inline]
#[stable(feature = "control_flow_enum", since = "1.83.0")]
pub fn break_value(self) -> Option<B> {
#[rustc_const_unstable(feature = "const_control_flow", issue = "148739")]
pub const fn break_value(self) -> Option<B>
where
Self: [const] Destruct,
{
match self {
ControlFlow::Continue(..) => None,
ControlFlow::Break(x) => Some(x),
Expand Down Expand Up @@ -268,7 +273,11 @@ impl<B, C> ControlFlow<B, C> {
/// to the break value in case it exists.
#[inline]
#[stable(feature = "control_flow_enum", since = "1.83.0")]
pub fn map_break<T>(self, f: impl FnOnce(B) -> T) -> ControlFlow<T, C> {
#[rustc_const_unstable(feature = "const_control_flow", issue = "148739")]
pub const fn map_break<T, F>(self, f: F) -> ControlFlow<T, C>
where
F: [const] FnOnce(B) -> T + [const] Destruct,
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@hkBst hkBst Oct 30, 2025

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Might it be good to have something like [const] (A+B+C)?

{
match self {
ControlFlow::Continue(x) => ControlFlow::Continue(x),
ControlFlow::Break(x) => ControlFlow::Break(f(x)),
Expand All @@ -288,7 +297,11 @@ impl<B, C> ControlFlow<B, C> {
/// ```
#[inline]
#[stable(feature = "control_flow_enum", since = "1.83.0")]
pub fn continue_value(self) -> Option<C> {
#[rustc_const_unstable(feature = "const_control_flow", issue = "148739")]
pub const fn continue_value(self) -> Option<C>
where
Self: [const] Destruct,
{
match self {
ControlFlow::Continue(x) => Some(x),
ControlFlow::Break(..) => None,
Expand Down Expand Up @@ -372,7 +385,11 @@ impl<B, C> ControlFlow<B, C> {
/// to the continue value in case it exists.
#[inline]
#[stable(feature = "control_flow_enum", since = "1.83.0")]
pub fn map_continue<T>(self, f: impl FnOnce(C) -> T) -> ControlFlow<B, T> {
#[rustc_const_unstable(feature = "const_control_flow", issue = "148739")]
pub const fn map_continue<T, F>(self, f: F) -> ControlFlow<B, T>
where
F: [const] FnOnce(C) -> T + [const] Destruct,
{
match self {
ControlFlow::Continue(x) => ControlFlow::Continue(f(x)),
ControlFlow::Break(x) => ControlFlow::Break(x),
Expand Down
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