[BugFix] Fix indexing with ghostlayers

The Block indexing has bug when created with an iteration slice and ghost layers. With !341 (merged) The Block indexing supports slices more naturally by limiting the iteration space to the sliced size. Thus the counter index is multiplied by the step size. This was done also for the offset of the ghostlayers which is wrong.

This MR fixes the problem

pystencils/cpu/kernelcreation.py

@@ -3,7 +3,6 @@ from typing import Union
 import sympy as sp
 
 import pystencils.astnodes as ast
-from pystencils.simp.assignment_collection import AssignmentCollection
 from pystencils.config import CreateKernelConfig
 from pystencils.enums import Target, Backend
 from pystencils.astnodes import Block, KernelFunction, LoopOverCoordinate, SympyAssignment
@@ -94,7 +93,7 @@ def create_kernel(assignments: Union[NodeCollection],
     return ast_node
 
 
-def create_indexed_kernel(assignments: Union[AssignmentCollection, NodeCollection],
+def create_indexed_kernel(assignments: NodeCollection,
                           config: CreateKernelConfig) -> KernelFunction:
     """
     Similar to :func:`create_kernel`, but here not all cells of a field are updated but only cells with
@@ -115,19 +114,38 @@ def create_indexed_kernel(assignments: Union[AssignmentCollection, NodeCollectio
     fields_written = assignments.bound_fields
     fields_read = assignments.rhs_fields
 
+    Index_IDBefore = ""
+    for index_field in index_fields:
+        Index_IDBefore += f"index field name: {index_field.name}: {str(id(index_field))}"
+
     assignments = assignments.all_assignments
     assignments = add_types(assignments, config)
 
     all_fields = fields_read.union(fields_written)
+    AllFieldsIDSBefore = ""
+    for field in all_fields:
+        AllFieldsIDSBefore += f"field name: {field.name}: {str(id(field))}"
 
     for index_field in index_fields:
         index_field.field_type = FieldType.INDEXED
         assert FieldType.is_indexed(index_field)
         assert index_field.spatial_dimensions == 1, "Index fields have to be 1D"
 
+    Index_IDAfter = ""
+    for index_field in index_fields:
+        Index_IDAfter += f"index field name: {index_field.name}: {str(id(index_field))}"
     non_index_fields = [f for f in all_fields if f not in index_fields]
     spatial_coordinates = {f.spatial_dimensions for f in non_index_fields}
-    assert len(spatial_coordinates) == 1, "Non-index fields do not have the same number of spatial coordinates"
+    assert len(spatial_coordinates) == 1, f"Non-index fields do not have the same number of spatial coordinates " \
+                                          f"Non index fields are {non_index_fields}, spatial coordinates are " \
+                                          f"{spatial_coordinates} and len(spatial coordiantes) is " \
+                                          f"{len(spatial_coordinates)}, " \
+                                          f"index_fields in config: {config.index_fields}, " \
+                                          f"extracted index fields: {index_fields} " \
+                                          f"Index_IDBefore {Index_IDBefore} " \
+                                          f"Index_IDAfter {Index_IDAfter} " \
+                                          f"AllFieldsIDSBefore {AllFieldsIDSBefore}"
+
     spatial_coordinates = list(spatial_coordinates)[0]
 
     def get_coordinate_symbol_assignment(name):