fix memory layout descriptor parsing (v2.0-dev edition)

Same as !431 (merged), but for pystencils 2.0

tests/frontend/test_field.py

@@ -205,6 +205,14 @@ def test_spatial_memory_layout_descriptors():
         == (0, 1, 2)
     )
 
+    assert spatial_layout_string_to_tuple("C", 5) == (0, 1, 2, 3, 4)
+
+    with pytest.raises(ValueError):
+        spatial_layout_string_to_tuple("aos", -1)
+
+    with pytest.raises(ValueError):
+        spatial_layout_string_to_tuple("aos", 4)
+
 
 def test_memory_layout_descriptors():
     assert (
@@ -229,6 +237,14 @@ def test_memory_layout_descriptors():
         == (0, 1, 2, 3)
     )
 
+    assert layout_string_to_tuple("C", 5) == (0, 1, 2, 3, 4)
+
+    with pytest.raises(ValueError):
+        layout_string_to_tuple("aos", -1)
+
+    with pytest.raises(ValueError):
+        layout_string_to_tuple("aos", 5)
+
 
 def test_staggered():