fix field for FieldIterators

Author: 9il

source/mir/ndslice/iterator.d

@@ -813,18 +813,18 @@ struct FieldIterator(Field)
     static alias __map(alias fun) = FieldIterator__map!(Field, fun);
 
     ///
-    _Slice!() opSlice()(size_t a, size_t b)
+    _Slice!() opSlice(size_t dimension)(size_t i, size_t j) const
     {
-        return typeof(return)(a, b);
+        return typeof(return)(i, j);
     }
 
     /++
     Returns:
-        `_field[slice.i .. slice.j]`.
+        `_field[_index + sl.i .. _index + sl.j]`.
     +/
-    auto opIndex()(_Slice!() slice)
+    auto opIndex()(_Slice!() sl)
     {
-        return _field[_index + slice.i .. _index + slice.j];
+        return _field[_index + sl.i .. _index + sl.j];
     }
 
     auto ref opUnary(string op : "*")()

source/mir/ndslice/slice.d

@@ -796,6 +796,24 @@ struct Slice(SliceKind kind, size_t[] packs, Iterator)
         }
     }
 
+    ///
+    unittest
+    {
+        auto arr = [1, 2, 3, 4];
+        auto sl0 = arr.sliced;
+        auto sl1 = arr.slicedField;
+
+        assert(sl0.field is arr);
+        assert(sl1.field is arr);
+
+        arr = arr[1 .. $];
+        sl0 = sl0[1 .. $];
+        sl1 = sl1[1 .. $];
+
+        assert(sl0.field is arr);
+        assert(sl1.field is arr);
+    }
+
     /++
     Returns: static array of lengths
     See_also: $(LREF .Slice.structure)