---

yaml
---
r: 32673
b: refs/heads/dist-snap
c: 53abb5e
h: refs/heads/master
i:
  32671: 08349aa
v: v3

Author: nikomatsakis

[refs]

@@ -7,6 +7,6 @@ refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
 refs/heads/try2: d0c6ce338884ee21843f4b40bf6bf18d222ce5df
 refs/heads/incoming: d9317a174e434d4c99fc1a37fd7dc0d2f5328d37
-refs/heads/dist-snap: 8d4928f7808813de62fefcb89139bfb7382b250b
+refs/heads/dist-snap: 53abb5edbd2079fdcc1c2887cf0a89aad75d6ea1
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/dist-snap/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
+        }
     }
 }