Correct error raised when slicing CLI arrays (IronLanguages#1827)

Src/IronPython/Runtime/Operations/ArrayOps.cs

@@ -429,7 +429,11 @@ private static Array GetSlice(Array data, Slice slice) {
         private static int[] TupleToIndices(Array a, IList<object?> tuple) {
             int[] indices = new int[tuple.Count];
             for (int i = 0; i < indices.Length; i++) {
-                int iindex = Converter.ConvertToInt32(tuple[i]);
+                object? oindex = tuple[i];
+                if (a.Rank != 1 && oindex is Slice) {
+                    throw PythonOps.NotImplementedError("slice on multi-dimensional array");
+                }
+                int iindex = Converter.ConvertToInt32(oindex);
                 indices[i] = i < a.Rank ? FixIndex(a, iindex, i) : int.MinValue;
             }
             return indices;

Tests/test_array.py

@@ -166,12 +166,14 @@ def test_slice(self):
         def f(): array1[::2] = [x * 2 for x in range(11)]
         self.assertRaises(ValueError, f)
 
-        # slices on non-1-dim arrays are not supported
+        # slices on non-1D arrays are not supported yet
         array2 = System.Array.CreateInstance(int, 20, 20)
-        self.assertRaises(NotImplementedError, lambda: array2[:]) # TODO: TypeError?
-        self.assertRaises(TypeError, lambda: array2[:, :])        # TODO: NotImplementedError? This would work in Numpy and Sympy
-        self.assertRaises(TypeError, lambda: array2[:, :, :])     # OK
-
+        # TODO: memoryview can slice ND views with a single slice
+        self.assertRaises(NotImplementedError, lambda: array2[:])
+        # TODO: Numpy and Sympy can slice ND arrays with exactly N slices
+        self.assertRaises(NotImplementedError, lambda: array2[:, :])
+        # TODO: Error matches memoryview; if slicing of ND arrays were supported, TypeError here would be expected
+        self.assertRaises(NotImplementedError, lambda: array2[:, :, :])
 
     def test_creation(self):
         t = System.Array