From 0e60287b4136bcede0c5eae8ab4e5de8496a16f0 Mon Sep 17 00:00:00 2001
From: Simon Sapin <simon.sapin@exyr.org>
Date: Tue, 23 Jan 2018 17:49:43 +0100
Subject: [PATCH] Implement Display for PanicInfo and Location
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Due to being in libcore,
this impl cannot access PanicInfo::payload if it’s a String.
---
 src/libcore/panic.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/libcore/panic.rs b/src/libcore/panic.rs
index 2dfd950225c..cf8ceff6cda 100644
--- a/src/libcore/panic.rs
+++ b/src/libcore/panic.rs
@@ -120,6 +120,23 @@ pub fn location(&self) -> Option<&Location> {
     }
 }
 
+impl<'a> fmt::Display for PanicInfo<'a> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("panicked at ")?;
+        if let Some(message) = self.message {
+            write!(formatter, "'{}', ", message)?
+        } else if let Some(payload) = self.payload.downcast_ref::<&'static str>() {
+            write!(formatter, "'{}', ", payload)?
+        }
+        // NOTE: we cannot use downcast_ref::<String>() here
+        // since String is not available in libcore!
+        // A String payload and no message is what we’d get from `std::panic!`
+        // called with multiple arguments.
+
+        self.location.fmt(formatter)
+    }
+}
+
 /// A struct containing information about the location of a panic.
 ///
 /// This structure is created by the [`location`] method of [`PanicInfo`].
@@ -226,3 +243,9 @@ pub fn column(&self) -> u32 {
         self.col
     }
 }
+
+impl<'a> fmt::Display for Location<'a> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "{}:{}:{}", self.file, self.line, self.col)
+    }
+}
-- 
2.44.0