Implement ExactSizeIterator and FusedIterator for repeated fields.

PiperOrigin-RevId: 591306340

rust/repeated.rs

@@ -7,6 +7,7 @@
 
 use std::fmt::{self, Debug};
 use std::iter;
+use std::iter::FusedIterator;
 /// Repeated scalar fields are implemented around the runtime-specific
 /// `RepeatedField` struct. `RepeatedField` stores an opaque pointer to the
 /// runtime-specific representation of a repeated scalar (`upb_Array*` on upb,
@@ -367,6 +368,14 @@ where
     }
 }
 
+impl<'msg, T: ?Sized + ProxiedInRepeated> ExactSizeIterator for RepeatedIter<'msg, T> {
+    fn len(&self) -> usize {
+        self.view.len()
+    }
+}
+
+impl<'msg, T: ?Sized + ProxiedInRepeated> FusedIterator for RepeatedIter<'msg, T> {}
+
 impl<'msg, T> iter::IntoIterator for RepeatedView<'msg, T>
 where
     T: ProxiedInRepeated + ?Sized + 'msg,

rust/test/shared/accessors_repeated_test.rs

@@ -21,6 +21,7 @@ macro_rules! generate_repeated_numeric_test {
               let mut mutator = msg.[<repeated_ $field _mut >]();
               mutator.push(1 as $t);
               assert_that!(mutator.len(), eq(1));
+              assert_that!(mutator.iter().len(), eq(1));
               assert_that!(mutator.get(0), some(eq(1 as $t)));
               mutator.set(0, 2 as $t);
               assert_that!(mutator.get(0), some(eq(2 as $t)));