librustc: Make &fn by-copy by default and remove the mode from frame_address.

src/libcore/stackwalk.rs

@@ -93,7 +93,10 @@ pub mod rustrt {
 pub mod rusti {
     #[abi = "rust-intrinsic"]
     pub extern "rust-intrinsic" {
+        #[cfg(stage0)]
         pub fn frame_address(f: &once fn(x: *u8));
+        #[cfg(not(stage0))]
+        pub fn frame_address(+f: &once fn(x: *u8));
     }
 }
 

src/librustc/middle/ty.rs

@@ -1259,14 +1259,6 @@ pub fn mach_sty(cfg: @session::config, t: t) -> sty {
 }
 
 pub fn default_arg_mode_for_ty(tcx: ctxt, ty: ty::t) -> ast::rmode {
-    // FIXME(#2202) --- We retain by-ref for &fn things to workaround a
-    // memory leak that otherwise results when @fn is upcast to &fn.
-    match ty::get(ty).sty {
-        ty::ty_closure(ClosureTy {sigil: ast::BorrowedSigil, _}) => {
-            return ast::by_ref;
-        }
-        _ => {}
-    }
     return if tcx.legacy_modes {
         if type_is_borrowed(ty) {
             // the old mode default was ++ for things like &ptr, but to be

src/librustc/middle/typeck/check/mod.rs

@@ -3496,7 +3496,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
                 output: ty::mk_nil()
             }
         });
-        (0u, ~[arg(ast::by_ref, fty)], ty::mk_nil())
+        (0u, ~[arg(ast::by_copy, fty)], ty::mk_nil())
       }
       ~"morestack_addr" => {
         (0u, ~[], ty::mk_nil_ptr(ccx.tcx))