Add checked_norem_div method for integer types

Author: newpavlov

library/core/src/num/int_macros.rs

@@ -668,6 +668,40 @@ macro_rules! int_impl {
             }
         }
 
+        /// Checked integer division. Computes `self / rhs`, returning `None` if one `rhs == 0`,
+        /// the division results in overflow, or remainder is not zero.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        #[doc = concat!("assert_eq!((", stringify!($SelfT), "::MIN + 1).checked_div(-1), Some(", stringify!($Max), "));")]
+        #[doc = concat!("assert_eq!(-5", stringify!($SelfT), ".checked_div(2), None);")]
+        #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.checked_div(-1), None);")]
+        #[doc = concat!("assert_eq!((1", stringify!($SelfT), ").checked_div(0), None);")]
+        /// ```
+        #[unstable(
+            feature = "checked_norem_div",
+            issue = "1",
+        )]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline]
+        pub const fn checked_norem_div(self, rhs: Self) -> Option<Self> {
+            if unlikely!(rhs == 0 || ((self == Self::MIN) && (rhs == -1))) {
+                None
+            } else {
+                // SAFETY: div by zero and by INT_MIN have been checked above
+                unsafe {
+                    if unlikely!(intrinsics::unchecked_rem(self, rhs) == 0) {
+                        None
+                    } else {
+                        Some(intrinsics::unchecked_div(self, rhs))
+                    }
+                }
+            }
+        }
         /// Checked integer remainder. Computes `self % rhs`, returning `None` if
         /// `rhs == 0` or the division results in overflow.
         ///

library/core/src/num/uint_macros.rs

@@ -654,6 +654,40 @@ macro_rules! uint_impl {
             }
         }
 
+        /// Checked integer division. Computes `self / rhs`, returning `None`
+        /// if `rhs == 0` or if division remainder is not zero.
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        #[doc = concat!("assert_eq!(128", stringify!($SelfT), ".checked_div(2), Some(64));")]
+        #[doc = concat!("assert_eq!(129", stringify!($SelfT), ".checked_div(2), None);")]
+        #[doc = concat!("assert_eq!(1", stringify!($SelfT), ".checked_div(0), None);")]
+        /// ```
+        #[unstable(
+            feature = "checked_norem_div",
+            issue = "1",
+        )]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline]
+        pub const fn checked_norem_div(self, rhs: Self) -> Option<Self> {
+            if unlikely!(rhs == 0) {
+                None
+            } else {
+                // SAFETY: div by zero has been checked above and unsigned types have no other
+                // failure modes for division
+                unsafe {
+                    if unlikely!(intrinsics::unchecked_rem(self, rhs) == 0) {
+                        None
+                    } else {
+                        Some(intrinsics::unchecked_div(self, rhs))
+                    }
+                }
+            }
+        }
 
         /// Checked integer remainder. Computes `self % rhs`, returning `None`
         /// if `rhs == 0`.