Avoid unwrapping in PanicInfo doc example.

Fixes https://github.com/rust-lang/rust/issues/51768.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/libcore/panic.rs b/src/libcore/panic.rs
index 1b4129b99fc..10f02ca2fdc 100644
--- a/src/libcore/panic.rs
+++ b/src/libcore/panic.rs
@@ -30,7 +30,11 @@ use fmt;
 /// use std::panic;
 ///
 /// panic::set_hook(Box::new(|panic_info| {
-///     println!("panic occurred: {:?}", panic_info.payload().downcast_ref::<&str>().unwrap());
+///     if let Some(s) = panic_info.payload().downcast_ref::<&str>() {
+///         println!("panic occurred: {:?}", s);
+///     } else {
+///         println!("panic occurred");
+///     }
 /// }));
 ///
 /// panic!("Normal panic");