diff -r c0301da04883 -r 7b2ee3e84c5f src/maputil.rs
--- a/src/maputil.rs	Fri Dec 06 15:30:23 2024 -0500
+++ b/src/maputil.rs	Fri Dec 06 16:14:41 2024 -0500
@@ -2,6 +2,7 @@
 Utilities for mapping over various container types.
 */
 
+#[cfg(feature = "nightly")]
 use std::mem::MaybeUninit;
 use itertools::izip;
 
@@ -322,8 +323,13 @@
 ///
 /// If `iter.next()` panicks, all items already yielded by the iterator are
 /// dropped.
+#[cfg(feature = "nightly")]
 #[inline]
-pub(crate) fn collect_into_array_unchecked<T, I : Iterator<Item=T>, const N: usize>(mut iter: I) -> [T; N]
+pub(crate) fn collect_into_array_unchecked<
+    T,
+    I : Iterator<Item=T>,
+    const N: usize
+>(mut iter: I) -> [T; N]
 {
     if N == 0 {
         // SAFETY: An empty array is always inhabited and has no validity invariants.
@@ -375,6 +381,19 @@
     unreachable!("Something went wrong with iterator length")
 }
 
+#[cfg(not(feature = "nightly"))]
+#[inline]
+pub(crate) fn collect_into_array_unchecked<
+    T,
+    I : Iterator<Item=T>,
+    const N: usize
+>(iter: I) -> [T; N]
+{
+    match iter.collect::<Vec<T>>().try_into() {
+        Ok(a) => a,
+        Err(_) => panic!("collect_into_array failure: should not happen"),
+    }
+}
 
 #[cfg(test)]
 mod tests {