Expression: Add a defensive assert in the idenitity mapper

loki/expression/mappers.py

@@ -559,6 +559,7 @@ def map_variable_symbol(self, expr, *args, **kwargs):
         new_type = expr.type
         if recurse_to_declaration_attributes:
             old_type = expr.type
+            assert expr.type is not None
             kind = self.rec(old_type.kind, *args, **kwargs)
 
             if expr.scope and expr.name == old_type.initial: