`f(kw=a, *b)` with keyword argument before star arguments isn’t evaluated left-to-right

def f(a, kw):
    pass

f(kw=print(1), *[print(2)])

In Python 3.4.10 and earlier, this prints 1 then 2, but in Python 3.5.0 and later, this prints 2 then 1.

This seems like a bug of some kind. Given that ast.parse() doesn’t distinguish between f(kw=a, *b) and f(*b, kw=a), perhaps the bug is that a keyword argument is allowed before star arguments at all—we already disallow f(kw=a, b), f(**a, b), and f(**a, *b).

首先在受影响的 Python 版本上复现所提供的 f(kw=print(1), *[print(2)]) 示例，然后跟踪 CPython 如何解析和求值包含关键字参数和星号参数的调用。当行为得到一致修正，或者在所选解决方案是拒绝无效参数顺序的情况下拒绝该顺序时，即视为完成；该 issue 未指定源文件或测试。