rust-cpython: replace dyn Iterator<..> of sequence with concrete type

We wouldn't care the cost of the dynamic dispatch, but I feel a concrete
type helps understanding error messages.

rust/hg-cpython/src/dirstate/dirs_multiset.rs

@@ -18,7 +18,10 b' use cpython::{'
 
 use crate::dirstate::extract_dirstate;
 use crate::ref_sharing::{PySharedRefCell, PySharedState};
-use hg::{DirsMultiset, DirstateMapError, DirstateParseError, EntryState};
+use hg::{
+    DirsMultiset, DirsMultisetIter, DirstateMapError, DirstateParseError,
+    EntryState,
+};
 
 py_class!(pub class Dirs |py| {
     data inner: PySharedRefCell<DirsMultiset>;
@@ -90,7 +93,7 b' py_class!(pub class Dirs |py| {'
         DirsMultisetKeysIterator::create_instance(
             py,
             RefCell::new(Some(leak_handle)),
-            RefCell::new(Box::new(leaked_ref.iter())),
+            RefCell::new(leaked_ref.iter()),
         )
     }
 
@@ -118,10 +121,10 b' impl Dirs {'
     }
 }
 
-py_shared_sequence_iterator!(
+py_shared_iterator_impl!(
     DirsMultisetKeysIterator,
     DirsMultisetLeakedRef,
-    Vec<u8>,
+    DirsMultisetIter<'static>,
     Dirs::translate_key,
     Option<PyBytes>
 );

rust/hg-cpython/src/ref_sharing.rs

@@ -417,23 +417,3 b' macro_rules! py_shared_mapping_iterator '
         );
     };
 }
-
-/// Works basically the same as `py_shared_mapping_iterator`, but with only a
-/// key.
-macro_rules! py_shared_sequence_iterator {
-    (
-        $name:ident,
-        $leaked:ident,
-        $key_type: ty,
-        $success_func: path,
-        $success_type: ty
-    ) => {
-        py_shared_iterator_impl!(
-            $name,
-            $leaked,
-            Box<dyn Iterator<Item = &'static $key_type> + Send>,
-            $success_func,
-            $success_type
-        );
-    };
-}