From 85eca92c928a708af75c554808256eeca99f299c Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Tue, 20 Jun 2023 19:16:18 +0200
Subject: [PATCH] Change default panic handler message format.

---
 core/src/error.md            |  6 ++++--
 core/src/panic/panic_info.rs | 10 ++++++----
 std/src/error.rs             |  3 ++-
 std/src/panicking.rs         |  2 +-
 4 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/core/src/error.md b/core/src/error.md
index 78808d489..7771b8adc 100644
--- a/core/src/error.md
+++ b/core/src/error.md
@@ -93,7 +93,8 @@ information that is already communicated by the source error being
 unwrapped:
 
 ```text
-thread 'main' panicked at 'env variable `IMPORTANT_PATH` is not set: NotPresent', src/main.rs:4:6
+thread 'main' panicked at src/main.rs:4:6:
+env variable `IMPORTANT_PATH` is not set: NotPresent
 ```
 
 In this example we end up mentioning that an env variable is not set,
@@ -109,7 +110,8 @@ prevent the source error, we end up introducing new information that is
 independent from our source error.
 
 ```text
-thread 'main' panicked at 'env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`: NotPresent', src/main.rs:4:6
+thread 'main' panicked at src/main.rs:4:6:
+env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`: NotPresent
 ```
 
 In this example we are communicating not only the name of the
diff --git a/core/src/panic/panic_info.rs b/core/src/panic/panic_info.rs
index 5576adde8..c7f04f11e 100644
--- a/core/src/panic/panic_info.rs
+++ b/core/src/panic/panic_info.rs
@@ -147,16 +147,18 @@ impl<'a> PanicInfo<'a> {
 impl fmt::Display for PanicInfo<'_> {
     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
         formatter.write_str("panicked at ")?;
+        self.location.fmt(formatter)?;
         if let Some(message) = self.message {
-            write!(formatter, "'{}', ", message)?
+            formatter.write_str(":\n")?;
+            formatter.write_fmt(*message)?;
         } else if let Some(payload) = self.payload.downcast_ref::<&'static str>() {
-            write!(formatter, "'{}', ", payload)?
+            formatter.write_str(":\n")?;
+            formatter.write_str(payload)?;
         }
         // NOTE: we cannot use downcast_ref::<String>() here
         // since String is not available in core!
         // The payload is a String when `std::panic!` is called with multiple arguments,
         // but in that case the message is also available.
-
-        self.location.fmt(formatter)
+        Ok(())
     }
 }
diff --git a/std/src/error.rs b/std/src/error.rs
index 05f8fd8de..ee5eddebf 100644
--- a/std/src/error.rs
+++ b/std/src/error.rs
@@ -121,7 +121,8 @@ mod private {
 /// This example produces the following output:
 ///
 /// ```console
-/// thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: SuperError is here!: SuperErrorSideKick is here!', src/error.rs:34:40
+/// thread 'main' panicked at src/error.rs:34:40:
+/// called `Result::unwrap()` on an `Err` value: SuperError is here!: SuperErrorSideKick is here!
 /// note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 /// ```
 ///
diff --git a/std/src/panicking.rs b/std/src/panicking.rs
index 15285465c..6ff7b19f2 100644
--- a/std/src/panicking.rs
+++ b/std/src/panicking.rs
@@ -266,7 +266,7 @@ pub fn panic_hook_with_disk_dump(info: &PanicInfo<'_>, path: Option<&crate::path
     let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>");
 
     let write = |err: &mut dyn crate::io::Write, backtrace: Option<BacktraceStyle>| {
-        let _ = writeln!(err, "thread '{name}' panicked at '{msg}', {location}");
+        let _ = writeln!(err, "thread '{name}' panicked at {location}:\n{msg}");
 
         static FIRST_PANIC: AtomicBool = AtomicBool::new(true);