stmt_inferrer.py 文件源码

 复制代码def _delete_element(target, context, lineno, solver):
    """Remove (if needed) a target from the context

    Cases:
        - del var_name: remove its type mapping from the context directly.
        - del subscript:
                    * Tuple/String --> Immutable. Raise exception.
                    * List/Dict --> Do nothing to the context.
    """
    if isinstance(target, (ast.Tuple, ast.List)):  # Multiple deletions
        for elem in target.elts:
            _delete_element(elem, context, lineno, solver)
    elif isinstance(target, ast.Name):
        context.delete_type(target.id)
    elif isinstance(target, ast.Subscript):
        expr.infer(target, context, solver)
        indexed_type = expr.infer(target.value, context, solver)
        solver.add(axioms.delete_subscript(indexed_type, solver.z3_types),
                   fail_message="Deletion in line {}".format(lineno))
    elif isinstance(target, ast.Attribute):
        raise NotImplementedError("Attribute deletion is not supported.")