syntax: Add the Bug Report HOWTO URL to the ICE message

And also reference the bug report HOWTO in CONTRIBUTING.md

Author: catamorphism

CONTRIBUTING.md

@@ -1,3 +1,9 @@
+## How to submit a bug report
+
+If you're just reporting a bug, please see:
+
+https://github.com/mozilla/rust/wiki/HOWTO-submit-a-Rust-bug-report
+
 ## Pull request procedure
 
 Pull requests should be targeted at Rust's `master` branch.

src/libsyntax/diagnostic.rs

@@ -15,6 +15,9 @@ use std::io;
 use std::local_data;
 use extra::term;
 
+static BUG_REPORT_URL: &'static str =
+    "https://github.com/mozilla/rust/wiki/HOWTO-submit-a-Rust-bug-report";
+
 pub trait Emitter {
     fn emit(&self,
             cmsp: Option<(@codemap::CodeMap, Span)>,
@@ -143,7 +146,8 @@ impl handler for HandlerT {
 }
 
 pub fn ice_msg(msg: &str) -> ~str {
-    format!("internal compiler error: {}", msg)
+    format!("internal compiler error: {}\nThis message reflects a bug in the Rust compiler. \
+            \nWe would appreciate a bug report: {}", msg, BUG_REPORT_URL)
 }
 
 pub fn mk_span_handler(handler: @mut handler, cm: @codemap::CodeMap)