From e072d1fa4f5c6078e121b8c9fc3b5324a915470a Mon Sep 17 00:00:00 2001
From: Cecile Tonglet <cecile.tonglet@cecton.com>
Date: Wed, 1 Nov 2023 15:52:01 +0100
Subject: [PATCH] Make from_iter() optimized

---
 src/array.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/array.rs b/src/array.rs
index c4fe24b..a184017 100644
--- a/src/array.rs
+++ b/src/array.rs
@@ -46,8 +46,12 @@ impl<T: ImplicitClone + 'static> Default for IArray<T> {
 
 impl<T: ImplicitClone + 'static> FromIterator<T> for IArray<T> {
     fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Self {
-        let vec = it.into_iter().collect::<Vec<T>>();
-        Self::Rc(Rc::from(vec))
+        let mut it = it.into_iter();
+        if it.size_hint() == (1, Some(1)) {
+            Self::Single([it.next().unwrap()])
+        } else {
+            Self::Rc(Rc::from(it.collect::<Vec<T>>()))
+        }
     }
 }
 
@@ -394,6 +398,14 @@ mod test_array {
         let _array = [Rc::new(Item)].into_iter().collect::<IArray<Rc<Item>>>();
     }
 
+    #[test]
+    fn from_iter_is_optimized() {
+        let array_1 = [1].into_iter().collect::<IArray<u32>>();
+        assert!(matches!(array_1, IArray::Single(_)));
+        let array_2 = [1, 2].into_iter().collect::<IArray<u32>>();
+        assert!(matches!(array_2, IArray::Rc(_)));
+    }
+
     #[test]
     fn static_array() {
         const _ARRAY: IArray<u32> = IArray::Static(&[1, 2, 3]);