add array::try_from_iter to improve discoverability and ergonomics

library/core/src/array/mod.rs

@@ -961,3 +961,32 @@ fn iter_next_chunk_erased<T>(
     mem::forget(guard);
     Ok(())
 }
+
+/// Tries to create an array `[T; N]` from the items of `iter`. If and only if `iter` holds
+/// `>= N` items it returns `OK([T; N])`. Otherwise, `Err(IntoIter<T; N>)` is returned.
+///
+/// # Arguments
+///
+/// * `iter`: Type that implements `IntoIterator` where `Items = T`.
+///
+/// # Example
+///
+/// ```rust
+/// #![feature(try_from_iter)]
+/// let vec = vec![0, 1, 2, 3];
+/// let array = core::array::try_from_iter::<_, 4>(vec);
+/// assert!(array.is_ok());
+/// assert_eq!(array.unwrap(), [0, 1, 2, 3]);
+///
+/// let vec = vec![0, 1, 2];
+/// let array = core::array::try_from_iter::<_, 4>(vec);
+/// assert!(array.is_err());
+/// ```
+#[unstable(feature = "try_from_iter", issue = "none")]
+#[inline]
+pub fn try_from_iter<I, const N: usize>(iter: I) -> Result<[I::Item; N], IntoIter<I::Item, N>>
+where
+    I: IntoIterator,
+{
+    iter.into_iter().next_chunk()
+}

library/core/tests/array.rs

@@ -701,6 +701,18 @@ fn array_into_iter_rfold() {
     assert_eq!(s, 10432);
 }
 
+#[test]
+fn array_try_fill_from() {
+    let vec = vec![0, 1, 2, 3];
+    let array = core::array::try_from_iter::<_, 4>(vec);
+    assert!(array.is_ok());
+    assert_eq!(array.unwrap(), [0, 1, 2, 3]);
+
+    let vec = vec![0, 1, 2];
+    let array = core::array::try_from_iter::<_, 4>(vec);
+    assert!(array.is_err());
+}
+
 #[cfg(not(panic = "abort"))]
 #[test]
 fn array_map_drops_unmapped_elements_on_panic() {

library/core/tests/lib.rs

@@ -108,6 +108,7 @@
 #![feature(utf8_chunks)]
 #![feature(is_ascii_octdigit)]
 #![feature(get_many_mut)]
+#![feature(try_from_iter)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(fuzzy_provenance_casts)]