Rollup merge of #85096 - clarfonthey:const_unchecked, r=oli-obk

Make unchecked_{add,sub,mul} inherent methods unstably const

The intrinsics are marked as being stably const (even though they're not stable by nature of being intrinsics), but the currently-unstable inherent versions are not marked as const. This fixes this inconsistency. Split out of #85017,

r? `@oli-obk`

library/core/src/iter/range.rs

@@ -106,7 +106,7 @@ fn forward(start: Self, count: usize) -> Self {
     /// For any `a` and `n`, where no overflow occurs:
     ///
     /// * `Step::forward_unchecked(a, n)` is equivalent to `Step::forward(a, n)`
-    #[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")]
+    #[unstable(feature = "step_trait_ext", reason = "recently added", issue = "42168")]
     unsafe fn forward_unchecked(start: Self, count: usize) -> Self {
         Step::forward(start, count)
     }
@@ -178,7 +178,7 @@ fn backward(start: Self, count: usize) -> Self {
     /// For any `a` and `n`, where no overflow occurs:
     ///
     /// * `Step::backward_unchecked(a, n)` is equivalent to `Step::backward(a, n)`
-    #[unstable(feature = "unchecked_math", reason = "niche optimization path", issue = "none")]
+    #[unstable(feature = "step_trait_ext", reason = "recently added", issue = "42168")]
     unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
         Step::backward(start, count)
     }

library/core/src/lib.rs

@@ -77,6 +77,7 @@
 #![feature(const_float_classify)]
 #![feature(const_float_bits_conv)]
 #![feature(const_int_unchecked_arith)]
+#![feature(const_inherent_unchecked_arith)]
 #![feature(const_mut_refs)]
 #![feature(const_refs_to_cell)]
 #![feature(const_panic)]

library/core/src/num/int_macros.rs

@@ -412,12 +412,13 @@ pub const fn checked_add(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_add(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_add(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_add`.
             unsafe { intrinsics::unchecked_add(self, rhs) }
@@ -450,12 +451,13 @@ pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_sub(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_sub`.
             unsafe { intrinsics::unchecked_sub(self, rhs) }
@@ -488,12 +490,13 @@ pub const fn checked_mul(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_mul(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_mul`.
             unsafe { intrinsics::unchecked_mul(self, rhs) }

library/core/src/num/uint_macros.rs

@@ -422,12 +422,13 @@ pub const fn checked_add(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_add(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_add(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_add`.
             unsafe { intrinsics::unchecked_add(self, rhs) }
@@ -460,12 +461,13 @@ pub const fn checked_sub(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_sub(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_sub`.
             unsafe { intrinsics::unchecked_sub(self, rhs) }
@@ -498,12 +500,13 @@ pub const fn checked_mul(self, rhs: Self) -> Option<Self> {
         #[unstable(
             feature = "unchecked_math",
             reason = "niche optimization path",
-            issue = "none",
+            issue = "85122",
         )]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
+        #[rustc_const_unstable(feature = "const_inherent_unchecked_arith", issue = "85122")]
         #[inline(always)]
-        pub unsafe fn unchecked_mul(self, rhs: Self) -> Self {
+        pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             // SAFETY: the caller must uphold the safety contract for
             // `unchecked_mul`.
             unsafe { intrinsics::unchecked_mul(self, rhs) }

src/tools/tidy/src/features.rs

@@ -51,6 +51,14 @@ pub struct Feature {
     pub has_gate_test: bool,
     pub tracking_issue: Option<NonZeroU32>,
 }
+impl Feature {
+    fn tracking_issue_display(&self) -> impl fmt::Display {
+        match self.tracking_issue {
+            None => "none".to_string(),
+            Some(x) => x.to_string(),
+        }
+    }
+}
 
 pub type Features = HashMap<String, Feature>;
 
@@ -361,10 +369,12 @@ fn get_and_check_lib_features(
                     if f.tracking_issue != s.tracking_issue && f.level != Status::Stable {
                         tidy_error!(
                             bad,
-                            "{}:{}: mismatches the `issue` in {}",
+                            "{}:{}: `issue` \"{}\" mismatches the {} `issue` of \"{}\"",
                             file.display(),
                             line,
-                            display
+                            f.tracking_issue_display(),
+                            display,
+                            s.tracking_issue_display(),
                         );
                     }
                 }