Added fn to normalize index calculation

Signed-off-by: Kaushal Phulgirkar <kaushalpp01@gmail.com>

stdlib/src/collections/list.mojo

@@ -235,9 +235,7 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
         """
         debug_assert(i <= self.size, "insert index out of range")
 
-        var normalized_idx = i
-        if i < 0:
-            normalized_idx = _max(0, len(self) + i)
+        var normalized_idx = self._normalize_index(i)
 
         var earlier_idx = len(self)
         var later_idx = len(self) - 1
@@ -307,9 +305,7 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
         """
         debug_assert(-len(self) <= i < len(self), "pop index out of range")
 
-        var normalized_idx = i
-        if i < 0:
-            normalized_idx += len(self)
+        var normalized_idx = self._normalize_index(i)
 
         var ret_val = move_from_pointee(self.data + normalized_idx)
         for j in range(normalized_idx + 1, self.size):
@@ -505,9 +501,7 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
         """
         debug_assert(-self.size <= i < self.size, "index must be within bounds")
 
-        var normalized_idx = i
-        if i < 0:
-            normalized_idx += len(self)
+        var normalized_idx = self._normalize_index(i)
 
         destroy_pointee(self.data + normalized_idx)
         initialize_pointee_move(self.data + normalized_idx, value^)
@@ -569,9 +563,7 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
         """
         debug_assert(-self.size <= i < self.size, "index must be within bounds")
 
-        var normalized_idx = i
-        if i < 0:
-            normalized_idx += len(self)
+        var normalized_idx = self._normalize_index(i)
 
         return (self.data + normalized_idx)[]
 
@@ -590,9 +582,7 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
         Returns:
             An immutable reference to the element at the given index.
         """
-        var normalized_idx = i
-        if i < 0:
-            normalized_idx += Reference(self)[].size
+        var normalized_idx = Reference(self)[]._normalize_index(i)
 
         var offset_ptr = Reference(self)[].data + normalized_idx
         return offset_ptr[]
@@ -666,3 +656,9 @@ struct List[T: CollectionElement](CollectionElement, Sized, Boolable):
                 result += ", "
         result += "]"
         return result
+
+    @always_inline
+    fn _normalize_index(self, index: Int) -> Int:
+        if index < 0:
+            return _max(0, len(self) + index)
+        return index

stdlib/test/collections/test_list.mojo

@@ -549,7 +549,7 @@ def test_2d_dynamic_list():
 
 def test_list_explicit_copy():
     var list = List[CopyCounter]()
-    list.append(CopyCounter()^)
+    list.append(CopyCounter())
     var list_copy = List(list)
     assert_equal(0, list.__get_ref(0)[].copy_count)
     assert_equal(1, list_copy.__get_ref(0)[].copy_count)