From 42e4007324b0158c4a1cc769d97bedbc2f3baeb5 Mon Sep 17 00:00:00 2001
From: Sean Griffin <sean@seantheprogrammer.com>
Date: Mon, 13 Feb 2017 13:48:19 -0500
Subject: [PATCH 1/3] Drop the `Sized` constraint on `impl Error for Box<T>`

Because of the implicit `Sized` constraint, `Box<Error>` does not
implement `Error`, which is potentially surprising when trying to pass
to a type which requires `T: Error`.
---
 src/libstd/error.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index e115263d2eb95..46f2d71270deb 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -278,7 +278,7 @@ impl Error for char::DecodeUtf16Error {
 }
 
 #[stable(feature = "box_error", since = "1.7.0")]
-impl<T: Error> Error for Box<T> {
+impl<T: Error + ?Sized> Error for Box<T> {
     fn description(&self) -> &str {
         Error::description(&**self)
     }

From 58e9a3b50d21a148f99aff09819f1186bff54f5f Mon Sep 17 00:00:00 2001
From: Sean Griffin <sean@seantheprogrammer.com>
Date: Mon, 13 Feb 2017 14:49:28 -0500
Subject: [PATCH 2/3] Allow the `From<Error>` impls on `Box<Error>` to be
 specialized

This attempts to address the coherence issues raised by
42e4007324b0158c4a1cc769d97bedbc2f3baeb5
---
 src/libstd/error.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 46f2d71270deb..bae370688f6ea 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -161,14 +161,14 @@ pub trait Error: Debug + Display {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, E: Error + 'a> From<E> for Box<Error + 'a> {
-    fn from(err: E) -> Box<Error + 'a> {
+    default fn from(err: E) -> Box<Error + 'a> {
         Box::new(err)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<Error + Send + Sync + 'a> {
-    fn from(err: E) -> Box<Error + Send + Sync + 'a> {
+    default fn from(err: E) -> Box<Error + Send + Sync + 'a> {
         Box::new(err)
     }
 }

From a60524eee60c57a002451c84a5ef78f4eb41ddaf Mon Sep 17 00:00:00 2001
From: Sean Griffin <sean@seantheprogrammer.com>
Date: Mon, 13 Feb 2017 15:13:39 -0500
Subject: [PATCH 3/3] Specialization needs to be enabled

---
 src/libstd/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 070690773b6c4..6bb512187f705 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -292,6 +292,7 @@
 #![feature(slice_bytes)]
 #![feature(slice_concat_ext)]
 #![feature(slice_patterns)]
+#![feature(specialization)]
 #![feature(staged_api)]
 #![feature(stmt_expr_attributes)]
 #![feature(str_char)]