Add an xfailed test case and a CONTRIBUTING.md file

CONTRIBUTING.md

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+## Pull request procedure
+
+Pull requests should be targeted at Rust's `incoming` branch (note that by default Github will aim them at the `master` branch) -- see "Changing The Commit Range and Destination Repository" in Github's documentation on [pull requests](https://help.github.com/articles/using-pull-requests). Before pushing to your Github repo and issuing the pull request, please do two things:
+
+1. [Rebase](http://git-scm.com/book/en/Git-Branching-Rebasing) your local changes against the `incoming` branch. Resolve any conflicts that arise.
+2. Run the full Rust test suite with the `make check` command. You're not off the hook even if you just stick to documentation; code examples in the docs are tested as well!
+
+Pull requests will be treated as "review requests", and we will give feedback we expect to see corrected on [style](https://github.com/mozilla/rust/wiki/Note-style-guide) and substance before pulling. Changes contributed via pull request should focus on a single issue at a time, like any other. We will not look kindly on pull-requests that try to "sneak" unrelated changes in.
+
+Normally, all pull requests must include regression tests (see [[Note-testsuite]]) that test your change. Occasionally, a change will be very difficult to test for. In those cases, please include a note in your commit message explaining why.
+
+For more details, please refer to [[Note-development-policy]].

src/test/run-pass/recursion.rs

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+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// xfail-test
+enum Nil {Nil}
+struct Cons<T> {head:int, tail:T}
+trait Dot {fn dot(other:self) -> int;}
+impl Nil:Dot {
+  fn dot(_:Nil) -> int {0}
+}
+impl<T:Dot> Cons<T>:Dot {
+  fn dot(other:Cons<T>) -> int {
+    self.head * other.head + self.tail.dot(other.tail)
+  }
+}
+fn test<T:Dot> (n:int, i:int, first:T, second:T) ->int {
+  match n {
+    0 => {first.dot(second)}
+      // Error message should be here. It should be a type error
+      // to instantiate `test` at a type other than T. (See #4287)
+    _ => {test (n-1, i+1, Cons {head:2*i+1, tail:first}, Cons{head:i*i, tail:second})}
+  }
+}
+fn main() {
+  let n = test(1, 0, Nil, Nil);
+  io::println(fmt!("%d", n));
+}