From 05e3248a7974f55b64f75a2483b37ff8c001a4ff Mon Sep 17 00:00:00 2001
From: Patrick Walton <pcwalton@mimiga.net>
Date: Wed, 25 Jun 2014 18:18:13 -0700
Subject: librustc: Match trait self types exactly.

This can break code that looked like:

    impl Foo for Box<Any> {
        fn f(&self) { ... }
    }

    let x: Box<Any + Send> = ...;
    x.f();

Change such code to:

    impl Foo for Box<Any> {
        fn f(&self) { ... }
    }

    let x: Box<Any> = ...;
    x.f();

That is, upcast before calling methods.

This is a conservative solution to #5781. A more proper treatment (see
the xfail'd `trait-contravariant-self.rs`) would take variance into
account. This change fixes the soundness hole.

Some library changes had to be made to make this work. In particular,
`Box<Any>` is no longer showable, and only `Box<Any+Send>` is showable.
Eventually, this restriction can be lifted; for now, it does not prove
too onerous, because `Any` is only used for propagating the result of
task failure.

This patch also adds a test for the variance inference work in #12828,
which accidentally landed as part of DST.

Closes #5781.

[breaking-change]
---
 src/libsyntax/diagnostic.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'src/libsyntax')

diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index 16c463f0c96..90569bfc132 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -18,6 +18,7 @@ use std::fmt;
 use std::io;
 use std::iter::range;
 use std::string::String;
+use term::WriterWrapper;
 use term;
 
 // maximum number of lines we will print for each error; arbitrary.
@@ -281,7 +282,7 @@ pub struct EmitterWriter {
 }
 
 enum Destination {
-    Terminal(Box<term::Terminal<Box<Writer + Send>> + Send>),
+    Terminal(Box<term::Terminal<WriterWrapper> + Send>),
     Raw(Box<Writer + Send>),
 }
 
-- 
cgit 1.4.1-3-g733a5