fixup! ayyyy one pass

Author: Nadrieril

compiler/rustc_mir_build/src/thir/pattern/usefulness.rs

@@ -39,11 +39,11 @@
 //! reachability for each subpattern and exhaustiveness for the whole match.
 //!
 //!
-//! # Illustrative Example
+//! # Example
 //!
 //! A picture is worth a thousand words. Let's watch the algorithm run before we dig into concepts.
 //!
-//! ```rust,ignore
+//! ```rust,ignore(example)
 //! match x {
 //!     Pair(Some(0), _) => 1,
 //!     Pair(_, false) => 2,
@@ -96,7 +96,7 @@
 //!  │ │ │ │
 //!  │ │ │ │ Dig into `true`:
 //!  │ │ │ ├─┐ Patterns:
-//!  │ │ │ │ │   <no rows left>
+//!  │ │ │ │ │   // no rows left
 //!  │ │ │ │ │
 //!  │ │ │ │ │ We have found an unmatched value! This gives us a witness.
 //!  │ │ │ │ │ New witnesses:
@@ -130,7 +130,7 @@
 //!  │ │ │
 //!  │ │ │ Dig into `true`:
 //!  │ │ ├─┐ Patterns:
-//!  │ │ │ │   <no rows left>
+//!  │ │ │ │   // no rows left
 //!  │ │ │ │
 //!  │ │ │ │ We have found an unmatched value! This gives us a witness.
 //!  │ │ │ │ New witnesses: