Nice reduction in general for the code.

I do suggest that you test the corresponding impact of this relaxation, if only to show positive examples as in the proposed PEP as well as where some errors go from SyntaxError to TypeError. For example:

>>> @True                                                                                                                                            .
... def f(a): return a*2
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: 'bool' object is not callable