Relax From<array> for SmallVec to allow different length arrays.

src/lib.rs

@@ -1909,9 +1909,17 @@ impl<'a, T: Clone, const N: usize> From<&'a [T]> for SmallVec<T, N> {
         slice.iter().cloned().collect()
     }
 }
-impl<T, const N: usize> From<[T; N]> for SmallVec<T, N> {
-    fn from(array: [T; N]) -> Self {
-        Self::from_buf(array)
+
+impl<T, const N: usize, const M: usize> From<[T; M]> for SmallVec<T, N> {
+    fn from(array: [T; M]) -> Self {
+        let mut this = Self::with_capacity(M);
+        let array = ManuallyDrop::new(array);
+        // SAFETY: M <= this.capacity()
+        unsafe {
+            copy_nonoverlapping(array.as_ptr(), this.as_mut_ptr(), M);
+            this.set_len(M);
+        }
+        this
     }
 }
 impl<T, const N: usize> From<Vec<T>> for SmallVec<T, N> {

src/tests.rs

@@ -656,6 +656,16 @@ fn test_from() {
     let small_vec: SmallVec<NoClone, 1> = SmallVec::from(vec);
     assert_eq!(&*small_vec, &[NoClone(42)]);
     drop(small_vec);
+
+    let array = [1; 128];
+    let small_vec: SmallVec<u8, 1> = SmallVec::from(array);
+    assert_eq!(&*small_vec, vec![1; 128].as_slice());
+    drop(small_vec);
+
+    let array = [99];
+    let small_vec: SmallVec<u8, 128> = SmallVec::from(array);
+    assert_eq!(&*small_vec, &[99u8]);
+    drop(small_vec);
 }
 
 #[test]