Add Option::is_some_with and Result::is_{ok,err}_with

library/core/src/option.rs

@@ -551,6 +551,29 @@ impl<T> Option<T> {
         matches!(*self, Some(_))
     }
 
+    /// Returns `true` if the option is a [`Some`] wrapping a value matching the predicate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_some_with)]
+    ///
+    /// let x: Option<u32> = Some(2);
+    /// assert_eq!(x.is_some_with(|&x| x > 1), true);
+    ///
+    /// let x: Option<u32> = Some(0);
+    /// assert_eq!(x.is_some_with(|&x| x > 1), false);
+    ///
+    /// let x: Option<u32> = None;
+    /// assert_eq!(x.is_some_with(|&x| x > 1), false);
+    /// ```
+    #[must_use]
+    #[inline]
+    #[unstable(feature = "is_some_with", issue = "93050")]
+    pub fn is_some_with(&self, f: impl FnOnce(&T) -> bool) -> bool {
+        matches!(self, Some(x) if f(x))
+    }
+
     /// Returns `true` if the option is a [`None`] value.
     ///
     /// # Examples

library/core/src/result.rs

@@ -542,6 +542,29 @@ impl<T, E> Result<T, E> {
         matches!(*self, Ok(_))
     }
 
+    /// Returns `true` if the result is [`Ok`] wrapping a value matching the predicate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_some_with)]
+    ///
+    /// let x: Result<u32, &str> = Ok(2);
+    /// assert_eq!(x.is_ok_with(|&x| x > 1), true);
+    ///
+    /// let x: Result<u32, &str> = Ok(0);
+    /// assert_eq!(x.is_ok_with(|&x| x > 1), false);
+    ///
+    /// let x: Result<u32, &str> = Err("hey");
+    /// assert_eq!(x.is_ok_with(|&x| x > 1), false);
+    /// ```
+    #[must_use]
+    #[inline]
+    #[unstable(feature = "is_some_with", issue = "93050")]
+    pub fn is_ok_with(&self, f: impl FnOnce(&T) -> bool) -> bool {
+        matches!(self, Ok(x) if f(x))
+    }
+
     /// Returns `true` if the result is [`Err`].
     ///
     /// # Examples
@@ -563,6 +586,30 @@ impl<T, E> Result<T, E> {
         !self.is_ok()
     }
 
+    /// Returns `true` if the result is [`Err`] wrapping a value matching the predicate.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(is_some_with)]
+    /// use std::io::{Error, ErrorKind};
+    ///
+    /// let x: Result<u32, Error> = Err(Error::new(ErrorKind::NotFound, "!"));
+    /// assert_eq!(x.is_err_with(|x| x.kind() == ErrorKind::NotFound), true);
+    ///
+    /// let x: Result<u32, Error> = Err(Error::new(ErrorKind::PermissionDenied, "!"));
+    /// assert_eq!(x.is_err_with(|x| x.kind() == ErrorKind::NotFound), false);
+    ///
+    /// let x: Result<u32, Error> = Ok(123);
+    /// assert_eq!(x.is_err_with(|x| x.kind() == ErrorKind::NotFound), false);
+    /// ```
+    #[must_use]
+    #[inline]
+    #[unstable(feature = "is_some_with", issue = "93050")]
+    pub fn is_err_with(&self, f: impl FnOnce(&E) -> bool) -> bool {
+        matches!(self, Err(x) if f(x))
+    }
+
     /////////////////////////////////////////////////////////////////////////
     // Adapter for each variant
     /////////////////////////////////////////////////////////////////////////