add Array::rev_iter (#1455)

builtin/array.mbt

@@ -1661,6 +1661,38 @@ pub fn iter[T](self : Array[T]) -> Iter[T] {
   })
 }
 
+///|
+/// Returns an iterator that yields elements from the array in reverse order,
+/// from the last element to the first.
+///
+/// Parameters:
+///
+/// * `array` : The array to iterate over in reverse order.
+///
+/// Returns an iterator that yields each element of the array, starting from the
+/// last element and moving towards the first.
+///
+/// Example:
+///
+/// ```moonbit
+/// test "Array::rev_iter" {
+///   let arr = [1, 2, 3]
+///   let result = []
+///   arr.rev_iter().each(fn(x) { result.push(x) })
+///   inspect!(result, content="[3, 2, 1]")
+/// }
+/// ```
+pub fn rev_iter[T](self : Array[T]) -> Iter[T] {
+  Iter::new(fn(yield_) {
+    for i = self.length() - 1; i >= 0; i = i - 1 {
+      guard let IterContinue = yield_(self.unsafe_get(i)) else { x => break x }
+
+    } else {
+      IterContinue
+    }
+  })
+}
+
 ///|
 /// Returns an iterator that provides both indices and values of the array in
 /// order.

builtin/builtin.mbti

@@ -107,6 +107,7 @@ impl Array {
   rev_fold[A, B](Self[A], init~ : B, (B, A) -> B) -> B
   rev_foldi[A, B](Self[A], init~ : B, (Int, B, A) -> B) -> B
   rev_inplace[T](Self[T]) -> Unit
+  rev_iter[T](Self[T]) -> Iter[T]
   search[T : Eq](Self[T], T) -> Int?
   search_by[T](Self[T], (T) -> Bool) -> Int?
   shrink_to_fit[T](Self[T]) -> Unit

immut/list/list.mbt

@@ -30,9 +30,11 @@ pub fn T::to_string[A : Show](xs : T[A]) -> String {
 ///|
 pub impl[A : ToJson] ToJson for T[A] with to_json(self) {
   let capacity = self.length()
-  guard capacity != 0 else { return Array([]) }
+  guard capacity != 0 else { return [] }
   let jsons = Array::new(capacity~)
-  self.each(fn(a) { jsons.push(a.to_json()) })
+  for a in self {
+    jsons.push(a.to_json())
+  }
   Array(jsons)
 }