Auto merge of #108095 - soc:drop-contains, r=Amanieu

Drop unstable `Option::contains`, `Result::contains`, `Result::contains_err`

This is a proposal to drop the three functions `Option::contains`, `Result::contains` and `Result::contains_err`.

The discovery of `Option::is_some_with`/`Result::is_ok_with`/`Result::is_err_with` in #93051 obviates the need for these methods (non-stabilization tracked in #62358).

An additional benefit of change is that it avoids spurious error messages in IDEs, when `contains` is supplied by a third-party library:
![option-result-unstable](https://user-images.githubusercontent.com/42493/219127961-13cb559e-6ee8-4449-8dc9-d28d07270ad5.png)

Author: bors

Diff for: library/core/src/option.rs

@@ -1780,36 +1780,6 @@ impl<T> Option<T> {
         mem::replace(self, Some(value))
     }
 
-    /// Returns `true` if the option is a [`Some`] value containing the given value.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(option_result_contains)]
-    ///
-    /// let x: Option<u32> = Some(2);
-    /// assert_eq!(x.contains(&2), true);
-    ///
-    /// let x: Option<u32> = Some(3);
-    /// assert_eq!(x.contains(&2), false);
-    ///
-    /// let x: Option<u32> = None;
-    /// assert_eq!(x.contains(&2), false);
-    /// ```
-    #[must_use]
-    #[inline]
-    #[unstable(feature = "option_result_contains", issue = "62358")]
-    #[rustc_const_unstable(feature = "const_option_ext", issue = "91930")]
-    pub const fn contains<U>(&self, x: &U) -> bool
-    where
-        U: ~const PartialEq<T>,
-    {
-        match self {
-            Some(y) => x.eq(y),
-            None => false,
-        }
-    }
-
     /// Zips `self` with another `Option`.
     ///
     /// If `self` is `Some(s)` and `other` is `Some(o)`, this method returns `Some((s, o))`.

Diff for: library/core/src/result.rs

@@ -1531,68 +1531,6 @@ impl<T, E> Result<T, E> {
             Err(e) => e,
         }
     }
-
-    /////////////////////////////////////////////////////////////////////////
-    // Misc or niche
-    /////////////////////////////////////////////////////////////////////////
-
-    /// Returns `true` if the result is an [`Ok`] value containing the given value.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(option_result_contains)]
-    ///
-    /// let x: Result<u32, &str> = Ok(2);
-    /// assert_eq!(x.contains(&2), true);
-    ///
-    /// let x: Result<u32, &str> = Ok(3);
-    /// assert_eq!(x.contains(&2), false);
-    ///
-    /// let x: Result<u32, &str> = Err("Some error message");
-    /// assert_eq!(x.contains(&2), false);
-    /// ```
-    #[must_use]
-    #[inline]
-    #[unstable(feature = "option_result_contains", issue = "62358")]
-    pub fn contains<U>(&self, x: &U) -> bool
-    where
-        U: PartialEq<T>,
-    {
-        match self {
-            Ok(y) => x == y,
-            Err(_) => false,
-        }
-    }
-
-    /// Returns `true` if the result is an [`Err`] value containing the given value.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(result_contains_err)]
-    ///
-    /// let x: Result<u32, &str> = Ok(2);
-    /// assert_eq!(x.contains_err(&"Some error message"), false);
-    ///
-    /// let x: Result<u32, &str> = Err("Some error message");
-    /// assert_eq!(x.contains_err(&"Some error message"), true);
-    ///
-    /// let x: Result<u32, &str> = Err("Some other error message");
-    /// assert_eq!(x.contains_err(&"Some error message"), false);
-    /// ```
-    #[must_use]
-    #[inline]
-    #[unstable(feature = "result_contains_err", issue = "62358")]
-    pub fn contains_err<F>(&self, f: &F) -> bool
-    where
-        F: PartialEq<E>,
-    {
-        match self {
-            Ok(_) => false,
-            Err(e) => f == e,
-        }
-    }
 }
 
 impl<T, E> Result<&T, E> {

Diff for: library/core/tests/lib.rs

@@ -95,7 +95,6 @@
 #![feature(portable_simd)]
 #![feature(ptr_metadata)]
 #![feature(once_cell)]
-#![feature(option_result_contains)]
 #![feature(unsized_tuple_coercion)]
 #![feature(const_option)]
 #![feature(const_option_ext)]