impl Debug for Map<_, [closure]>

This  matches the (implementation for `core::iter::Map`)[0].

[0]: https://github.com/rust-lang/rust/blob/eac35583d2ffb5ed9e564dee0822c9a244058ee0/library/core/src/iter/adapters/map.rs#L73-L78

Author: tamird

src/lib.rs

@@ -1073,12 +1073,18 @@ where
 
 /// An iterator which applies a fallible transform to the elements of the
 /// underlying iterator.
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Map<T, F> {
     it: T,
     f: F,
 }
 
+impl<I: core::fmt::Debug, F> core::fmt::Debug for Map<I, F> {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        f.debug_struct("Map").field("iter", &self.it).finish()
+    }
+}
+
 impl<T, F, B> FallibleIterator for Map<T, F>
 where
     T: FallibleIterator,

src/test.rs

@@ -190,6 +190,8 @@ fn last() {
 #[test]
 fn map() {
     let it = convert(vec![0, 1, 2, 3, 4].into_iter().map(Ok::<u32, ()>)).map(|n| Ok(n * 2));
+    fn assert_debug(_: &impl core::fmt::Debug) {}
+    assert_debug(&it);
     assert_eq!(it.clone().collect::<Vec<_>>().unwrap(), [0, 2, 4, 6, 8]);
     assert_eq!(it.rev().collect::<Vec<_>>().unwrap(), [8, 6, 4, 2, 0]);