---

yaml
---
r: 24011
b: refs/heads/master
c: 53abb5e
h: refs/heads/master
i:
  24009: 49e27cd
  24007: eb78e7e
v: v3

Author: nikomatsakis

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 8d4928f7808813de62fefcb89139bfb7382b250b
+refs/heads/master: 53abb5edbd2079fdcc1c2887cf0a89aad75d6ea1
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: cd6f24f9d14ac90d167386a56e7a6ac1f0318195
 refs/heads/try: ffbe0e0e00374358b789b0037bcb3a577cd218be

trunk/src/rustc/middle/ty.rs

@@ -1090,12 +1090,22 @@ pure fn mach_sty(cfg: @session::config, t: t) -> sty {
 }
 
 fn default_arg_mode_for_ty(tcx: ctxt, ty: ty::t) -> ast::rmode {
-    if ty::type_is_immediate(ty) {
+    return if ty::type_is_immediate(ty) {
         ast::by_val
-    } else if tcx.legacy_modes {
+    } else if tcx.legacy_modes || type_is_fn(ty) {
+        //                        ^^^^^^^^^^^^^^
+        // FIXME(#2202) --- We retain by-ref by default to workaround a memory
+        // leak that otherwise results when @fn is upcast to &fn.
         ast::by_ref
     } else {
         ast::by_copy
+    };
+
+    fn type_is_fn(ty: t) -> bool {
+        match get(ty).sty {
+            ty_fn(*) => true,
+            _ => false
+        }
     }
 }