use type-safe getData instead of uncheckedFastGetData

Fixes #4 (moved). The performance impact in release mode is negligible and type-checking is generally quite useful. Thanks to walberla/walberla!258 (merged), one can even use vector-valued fields in pystencils, which was unsupported before, but did not produce an error.

pystencils_walberla/jinja_filters.py

@@ -117,7 +117,7 @@ def field_extraction_code(field, is_temporary, declaration_only=False,
             return "%s * %s;" % (field_type, field_name)
         else:
             prefix = "" if no_declaration else "auto "
-            return "%s%s = block->uncheckedFastGetData< %s >(%sID);" % (prefix, field_name, field_type, field_name)
+            return "%s%s = block->getData< %s >(%sID);" % (prefix, field_name, field_type, field_name)
     else:
         assert field_name.endswith('_tmp')
         original_field_name = field_name[:-len('_tmp')]