Remove breakage example

Author: Mark-Simulacrum

library/core/src/convert/mod.rs

@@ -645,31 +645,7 @@ impl AsMut<str> for str {
 /// }
 /// ```
 ///
-/// # Future compatibility
-///
-/// This enum has the same role as [the `!` “never” type][never],
-/// which is unstable in this version of Rust.
-/// When `!` is stabilized, we plan to make `Infallible` a type alias to it:
-///
-/// ```ignore (illustrates future std change)
-/// pub type Infallible = !;
-/// ```
-///
-/// … and eventually deprecate `Infallible`.
-///
-/// However there is one case where `!` syntax can be used
-/// before `!` is stabilized as a full-fledged type: in the position of a function’s return type.
-/// Specifically, it is possible implementations for two different function pointer types:
-///
-/// ```
-/// trait MyTrait {}
-/// impl MyTrait for fn() -> ! {}
-/// impl MyTrait for fn() -> std::convert::Infallible {}
-/// ```
-///
-/// With `Infallible` being an enum, this code is valid.
-/// However when `Infallible` becomes an alias for the never type,
-/// the two `impl`s will start to overlap
-/// and therefore will be disallowed by the language’s trait coherence rules.
+/// This has the same role as [the `!` “never” type][never], and is in fact an
+/// alias to it. Generally speaking, you should prefer the never type.
 #[stable(feature = "convert_infallible", since = "1.34.0")]
 pub type Infallible = !;