remove #[old_impl_check] now that #21363 has been fixed

src/liballoc/boxed.rs

@@ -250,8 +250,6 @@ impl<T: ?Sized> DerefMut for Box<T> {
     fn deref_mut(&mut self) -> &mut T { &mut **self }
 }
 
-// FIXME(#21363) remove `old_impl_check` when bug is fixed
-#[old_impl_check]
 impl<'a, T> Iterator for Box<Iterator<Item=T> + 'a> {
     type Item = T;
 

src/liballoc/lib.rs

@@ -70,8 +70,6 @@
 #![feature(lang_items, unsafe_destructor)]
 #![feature(box_syntax)]
 #![feature(optin_builtin_traits)]
-// FIXME(#21363) remove `old_impl_check` when bug is fixed
-#![feature(old_impl_check)]
 #![allow(unknown_features)] #![feature(int_uint)]
 #![feature(core)]
 #![feature(hash)]

src/libcore/iter.rs

@@ -101,8 +101,6 @@ pub trait Iterator {
     fn size_hint(&self) -> (usize, Option<usize>) { (0, None) }
 }
 
-// FIXME(#21363) remove `old_impl_check` when bug is fixed
-#[old_impl_check]
 impl<'a, T> Iterator for &'a mut (Iterator<Item=T> + 'a) {
     type Item = T;
 

src/libcore/lib.rs

@@ -64,8 +64,6 @@
 #![feature(unboxed_closures)]
 #![allow(unknown_features)] #![feature(int_uint)]
 #![feature(on_unimplemented)]
-// FIXME(#21363) remove `old_impl_check` when bug is fixed
-#![feature(old_impl_check)]
 #![deny(missing_docs)]
 
 #[macro_use]