Fix example for unconditional_recursion

Author: alex-semenyuk

clippy_lints/src/unconditional_recursion.rs

@@ -23,8 +23,8 @@ declare_clippy_lint! {
  /// implementations.
  ///
  /// ### Why is this bad?
- /// This is a hard to find infinite recursion that will crash any code
- /// using it.
+ /// Infinite recursion in trait implementation will either cause crashes
+ /// or result in an infinite loop, and it is hard to detect.
  ///
  /// ### Example
  /// ```no_run
@@ -39,9 +39,31 @@ declare_clippy_lint! {
  /// }
  /// }
  /// ```
+ ///
  /// Use instead:
  ///
- /// In such cases, either use `#[derive(PartialEq)]` or don't implement it.
+ /// ```no_run
+ /// #[derive(PartialEq)]
+ /// enum Foo {
+ /// A,
+ /// B,
+ /// }
+ /// ```
+ ///
+ /// As an alternative, rewrite the logic without recursion:
+ ///
+ /// ```no_run
+ /// enum Foo {
+ /// A,
+ /// B,
+ /// }
+ ///
+ /// impl PartialEq for Foo {
+ /// fn eq(&self, other: &Self) -> bool {
+ /// matches!((self, other), (Foo::A, Foo::A) | (Foo::B, Foo::B))
+ /// }
+ /// }
+ /// ```
  #[clippy::version = "1.77.0"]
  pub UNCONDITIONAL_RECURSION,
  suspicious,