Implement System.Array constructor with base arg

Src/IronPython/Runtime/Operations/ArrayOps.cs

@@ -67,19 +67,23 @@ public static object __new__(CodeContext context, PythonType pythonType, ICollec
         }
 
         [StaticExtensionMethod]
-        public static object __new__(CodeContext context, PythonType pythonType, object items) {
+        public static object __new__(CodeContext context, PythonType pythonType, object items)
+            => __new__(context, pythonType, items, @base: 0);
+
+        [StaticExtensionMethod]
+        public static object __new__(CodeContext context, PythonType pythonType, object items, /*[KeywordOnly]*/ int @base) {
             Type type = pythonType.UnderlyingSystemType.GetElementType()!;
 
-            object? lenFunc;
-            if (!PythonOps.TryGetBoundAttr(items, "__len__", out lenFunc))
+            if (!PythonOps.TryGetBoundAttr(items, "__len__", out object? lenFunc))
                 throw PythonOps.TypeErrorForBadInstance("expected object with __len__ function, got {0}", items);
 
             int len = context.LanguageContext.ConvertToInt32(PythonOps.CallWithContext(context, lenFunc));
 
-            Array res = Array.CreateInstance(type, len);
+            Array res = @base == 0 ?
+                Array.CreateInstance(type, len) : Array.CreateInstance(type, [len], [@base]);
 
             IEnumerator ie = PythonOps.GetEnumerator(items);
-            int i = 0;
+            int i = @base;
             while (ie.MoveNext()) {
                 res.SetValue(Converter.Convert(ie.Current, type), i++);
             }
@@ -277,7 +281,7 @@ public static string __repr__(CodeContext/*!*/ context, [NotNone] Array/*!*/ sel
                     }
                     ret.Append(')');
                     if (self.GetLowerBound(0) != 0) {
-                        ret.Append(", base: ");
+                        ret.Append(", base=");
                         ret.Append(self.GetLowerBound(0));
                     }
                     ret.Append(')');

Tests/test_array.py

@@ -200,6 +200,26 @@ def test_constructor(self):
             for y in range(array3.GetLength(1)):
                 self.assertEqual(array3[x, y], 0)
 
+    def test_constructor_nonzero_lowerbound(self):
+        # 1-based
+        arr = System.Array[int]((1, 2), base=1)
+        self.assertEqual(arr.Rank, 1)
+        self.assertEqual(arr.Length, 2)
+        self.assertEqual(arr.GetLowerBound(0), 1)
+        self.assertEqual(arr.GetUpperBound(0), 2)
+        self.assertEqual(arr[1], 1)
+        self.assertEqual(arr[2], 2)
+        for i in range(1, 3):
+            self.assertEqual(arr[i], i)
+
+    def test_repr(self):
+        from System import Array
+        arr = Array[int]((5, 1), base=1)
+        s = repr(arr)
+        self.assertEqual(s, "Array[int]((5, 1), base=1)")
+        array4eval = eval(s, globals(), locals())
+        self.assertEqual(arr, array4eval)
+
     def test_nonzero_lowerbound(self):
         a = System.Array.CreateInstance(int, (5,), (5,))
         for i in range(5, 5 + a.Length): a[i] = i
@@ -210,7 +230,7 @@ def test_nonzero_lowerbound(self):
         self.assertEqual(a[-1:-3:-1], System.Array[int]((9,8)))
         self.assertEqual(a[-1], 9)
 
-        self.assertEqual(repr(a), 'Array[int]((5, 6, 7, 8, 9), base: 5)')
+        self.assertEqual(repr(a), 'Array[int]((5, 6, 7, 8, 9), base=5)')
 
         a = System.Array.CreateInstance(int, (5,), (15,))
         b = System.Array.CreateInstance(int, (5,), (20,))
@@ -322,9 +342,7 @@ def test_base_negative(self):
 
         # test slice indexing
         # 1-dim array [-1, 0, 1]
-        arr1 = System.Array.CreateInstance(int, (3,), (-1,))
-        for i in range(-1, 2):
-            arr1[i] = i
+        arr1 = System.Array[int]((-1, 0, 1), base=-1)
         self.assertEqual(arr1[-1:1], System.Array[int]((-1, 0)))
         self.assertEqual(arr1[-2:1], System.Array[int]((-1, 0)))
         self.assertEqual(arr1[0:], System.Array[int]((0, 1)))