Add a cleanup for copying closures. Closes #804.

src/comp/middle/trans.rs

@@ -6387,6 +6387,9 @@ fn trans_closure(bcx_maybe: &option::t[@block_ctxt],
 
         let closure = create_real_fn_pair(env.bcx, option::get(llfnty),
                                           llfndecl, env.ptr);
+        if copying {
+            add_clean_temp(bcx, closure, node_id_type(cx.ccx, id))
+        }
         some({fn_pair: closure, bcx: env.bcx})
       }
       _ { none }

src/test/run-pass/lambda-no-leak.rs

@@ -0,0 +1,7 @@
+// Make sure we don't leak lambdas in silly ways.
+fn force(f: &fn()) { f() }
+fn main() {
+    let x = 7;
+    lambda() { log_err x; };
+    force(lambda() { log_err x; });
+}