Rollup merge of #89876 - AlexApps99:const_ops, r=oli-obk

Make most std::ops traits const on numeric types

This PR makes existing implementations of `std::ops` traits (`Add`, `Sub`, etc) [`impl const`](#67792) where possible.
This affects:
- All numeric primitives (`u*`, `i*`, `f*`)
- `NonZero*`
- `Wrapping`

This is under the `rustc_const_unstable` feature `const_ops`.
I will write tests once I know what can and can't be kept for the final version of this PR.

Since this is my first PR to rustc (and hopefully one of many), please give me feedback on how to better handle the PR process wherever possible. Thanks

[Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Const.20std.3A.3Aops.20traits.20PR)

library/core/src/internal_macros.rs

@@ -5,6 +5,23 @@ macro_rules! forward_ref_unop {
         forward_ref_unop!(impl $imp, $method for $t,
                 #[stable(feature = "rust1", since = "1.0.0")]);
     };
+    (impl const $imp:ident, $method:ident for $t:ty) => {
+        forward_ref_unop!(impl const $imp, $method for $t,
+                #[stable(feature = "rust1", since = "1.0.0")]);
+    };
+    // Equivalent to the non-const version, with the addition of `rustc_const_unstable`
+    (impl const $imp:ident, $method:ident for $t:ty, #[$attr:meta]) => {
+        #[$attr]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl const $imp for &$t {
+            type Output = <$t as $imp>::Output;
+
+            #[inline]
+            fn $method(self) -> <$t as $imp>::Output {
+                $imp::$method(*self)
+            }
+        }
+    };
     (impl $imp:ident, $method:ident for $t:ty, #[$attr:meta]) => {
         #[$attr]
         impl $imp for &$t {
@@ -25,6 +42,45 @@ macro_rules! forward_ref_binop {
         forward_ref_binop!(impl $imp, $method for $t, $u,
                 #[stable(feature = "rust1", since = "1.0.0")]);
     };
+    (impl const $imp:ident, $method:ident for $t:ty, $u:ty) => {
+        forward_ref_binop!(impl const $imp, $method for $t, $u,
+                #[stable(feature = "rust1", since = "1.0.0")]);
+    };
+    // Equivalent to the non-const version, with the addition of `rustc_const_unstable`
+    (impl const $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
+        #[$attr]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl<'a> const $imp<$u> for &'a $t {
+            type Output = <$t as $imp<$u>>::Output;
+
+            #[inline]
+            fn $method(self, other: $u) -> <$t as $imp<$u>>::Output {
+                $imp::$method(*self, other)
+            }
+        }
+
+        #[$attr]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl const $imp<&$u> for $t {
+            type Output = <$t as $imp<$u>>::Output;
+
+            #[inline]
+            fn $method(self, other: &$u) -> <$t as $imp<$u>>::Output {
+                $imp::$method(self, *other)
+            }
+        }
+
+        #[$attr]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl const $imp<&$u> for &$t {
+            type Output = <$t as $imp<$u>>::Output;
+
+            #[inline]
+            fn $method(self, other: &$u) -> <$t as $imp<$u>>::Output {
+                $imp::$method(*self, *other)
+            }
+        }
+    };
     (impl $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
         #[$attr]
         impl<'a> $imp<$u> for &'a $t {
@@ -65,6 +121,21 @@ macro_rules! forward_ref_op_assign {
         forward_ref_op_assign!(impl $imp, $method for $t, $u,
                 #[stable(feature = "op_assign_builtins_by_ref", since = "1.22.0")]);
     };
+    (impl const $imp:ident, $method:ident for $t:ty, $u:ty) => {
+        forward_ref_op_assign!(impl const $imp, $method for $t, $u,
+                #[stable(feature = "op_assign_builtins_by_ref", since = "1.22.0")]);
+    };
+    // Equivalent to the non-const version, with the addition of `rustc_const_unstable`
+    (impl const $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
+        #[$attr]
+        #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+        impl const $imp<&$u> for $t {
+            #[inline]
+            fn $method(&mut self, other: &$u) {
+                $imp::$method(self, *other);
+            }
+        }
+    };
     (impl $imp:ident, $method:ident for $t:ty, $u:ty, #[$attr:meta]) => {
         #[$attr]
         impl $imp<&$u> for $t {

library/core/src/lib.rs

@@ -117,6 +117,7 @@
 #![feature(const_maybe_uninit_as_ptr)]
 #![feature(const_maybe_uninit_assume_init)]
 #![feature(const_num_from_num)]
+#![feature(const_ops)]
 #![feature(const_option)]
 #![feature(const_pin)]
 #![feature(const_replace)]

library/core/src/num/nonzero.rs

@@ -92,7 +92,8 @@ macro_rules! nonzero_integers {
             }
 
             #[stable(feature = "nonzero_bitor", since = "1.45.0")]
-            impl BitOr for $Ty {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const BitOr for $Ty {
                 type Output = Self;
                 #[inline]
                 fn bitor(self, rhs: Self) -> Self::Output {
@@ -103,7 +104,8 @@ macro_rules! nonzero_integers {
             }
 
             #[stable(feature = "nonzero_bitor", since = "1.45.0")]
-            impl BitOr<$Int> for $Ty {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const BitOr<$Int> for $Ty {
                 type Output = Self;
                 #[inline]
                 fn bitor(self, rhs: $Int) -> Self::Output {
@@ -115,7 +117,8 @@ macro_rules! nonzero_integers {
             }
 
             #[stable(feature = "nonzero_bitor", since = "1.45.0")]
-            impl BitOr<$Ty> for $Int {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const BitOr<$Ty> for $Int {
                 type Output = $Ty;
                 #[inline]
                 fn bitor(self, rhs: $Ty) -> Self::Output {
@@ -127,15 +130,17 @@ macro_rules! nonzero_integers {
             }
 
             #[stable(feature = "nonzero_bitor", since = "1.45.0")]
-            impl BitOrAssign for $Ty {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const BitOrAssign for $Ty {
                 #[inline]
                 fn bitor_assign(&mut self, rhs: Self) {
                     *self = *self | rhs;
                 }
             }
 
             #[stable(feature = "nonzero_bitor", since = "1.45.0")]
-            impl BitOrAssign<$Int> for $Ty {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const BitOrAssign<$Int> for $Ty {
                 #[inline]
                 fn bitor_assign(&mut self, rhs: $Int) {
                     *self = *self | rhs;
@@ -257,7 +262,8 @@ macro_rules! nonzero_integers_div {
     ( $( $Ty: ident($Int: ty); )+ ) => {
         $(
             #[stable(feature = "nonzero_div", since = "1.51.0")]
-            impl Div<$Ty> for $Int {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const Div<$Ty> for $Int {
                 type Output = $Int;
                 /// This operation rounds towards zero,
                 /// truncating any fractional part of the exact result, and cannot panic.
@@ -270,7 +276,8 @@ macro_rules! nonzero_integers_div {
             }
 
             #[stable(feature = "nonzero_div", since = "1.51.0")]
-            impl Rem<$Ty> for $Int {
+            #[rustc_const_unstable(feature = "const_ops", issue = "90080")]
+            impl const Rem<$Ty> for $Int {
                 type Output = $Int;
                 /// This operation satisfies `n % d == n - (n / d) * d`, and cannot panic.
                 #[inline]