From 0d39797dc0d787c8dde695a2c0ac1262fedc77cb Mon Sep 17 00:00:00 2001
From: Sean McArthur <sean@seanmonstar.com>
Date: Tue, 5 Mar 2019 19:33:22 -0800
Subject: [PATCH] libstd: implement Error::source for io::Error

---
 src/libstd/io/error.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libstd/io/error.rs b/src/libstd/io/error.rs
index fdc5625ff1841..614b79124cc68 100644
--- a/src/libstd/io/error.rs
+++ b/src/libstd/io/error.rs
@@ -556,6 +556,14 @@ impl error::Error for Error {
             Repr::Custom(ref c) => c.error.cause(),
         }
     }
+
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match self.repr {
+            Repr::Os(..) => None,
+            Repr::Simple(..) => None,
+            Repr::Custom(ref c) => c.error.source(),
+        }
+    }
 }
 
 fn _assert_error_is_sync_send() {