libstd: Remove "dual impls" from the language and enforce coherence rules. r=brson

"Dual impls" are impls that are both type implementations and trait
implementations. They can lead to ambiguity and so this patch removes them
from the language.

This also enforces coherence rules. Without this patch, records can implement
traits not defined in the current crate. This patch fixes this, and updates
all of rustc to adhere to the new enforcement. Most of this patch is fixing
rustc to obey the coherence rules, which involves converting a bunch of records
to structs.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libstd/ebml.rs b/src/libstd/ebml.rs
index dc379cec21b..f93705c0c62 100644
--- a/src/libstd/ebml.rs
+++ b/src/libstd/ebml.rs
@@ -676,6 +676,7 @@ pub mod writer {
 mod tests {
     use ebml::reader;
     use ebml::writer;
+    use serialize::Encodable;
     use serialize;
 
     use core::io;