auto merge of #5176 : brson/rust/unwrap_shared_mutable_state, r=nikomatsakis

r?

This fixes the current [random failures](http://buildbot.rust-lang.org/builders/auto-linux/builds/291/steps/test/logs/stdio) on the bots and closes #4436 by removing `unwrap_shared_mutable_state` and the code that depends on it. The result is that ARC-like things will not be unwrappable. This feature is complex and is not used outside of test cases.

Note that there is not consensus to remove it.

(second commit)

1 files changed, 5 insertions, 2 deletions

diff --git a/src/rt/rust_kernel.cpp b/src/rt/rust_kernel.cpp
index 4d2d6ad344c..761dbeade53 100644
--- a/src/rt/rust_kernel.cpp
+++ b/src/rt/rust_kernel.cpp
@@ -342,8 +342,11 @@ rust_kernel::register_exit_function(spawn_fn runner, fn_env_pair *f) {
     assert(!at_exit_started && "registering at_exit function after exit");
 
     if (at_exit_runner) {
-        assert(runner == at_exit_runner
-               && "there can be only one at_exit_runner");
+        // FIXME #2912 Would be very nice to assert this but we can't because
+        // of the way coretest works (the test case ends up using its own
+        // function)
+        //assert(runner == at_exit_runner
+        //       && "there can be only one at_exit_runner");
     }
 
     at_exit_runner = runner;