[Cython] CF based type inference
vitja.makarov at gmail.com
Thu May 10 09:27:58 CEST 2012
2012/5/10 Stefan Behnel <stefan_ml at behnel.de>:
> Vitja Makarov, 08.05.2012 15:47:
>> 2012/5/8 Stefan Behnel:
>>> Vitja has rebased the type inference on the control flow, so I wonder if
>>> this will enable us to properly infer this:
>>> def partial_validity():
>>> >>> partial_validity()
>>> ('Python object', 'double', 'str object')
>>> a = 1.0
>>> b = a + 2 # definitely double
>>> a = 'test'
>>> c = a + 'toast' # definitely str
>>> return typeof(a), typeof(b), typeof(c)
>>> I think, what is mainly needed for this is that a NameNode with an
>>> undeclared type should not report its own entry as dependency but that of
>>> its own cf_assignments. Would this work?
>>> (Haven't got the time to try it out right now, so I'm dumping it here.)
>> Yeah, that might work. The other way to go is to split entries:
>> def partial_validity():
>> >>> partial_validity()
>> ('str object', 'double', 'str object')
>> a_1 = 1.0
>> b = a_1 + 2 # definitely double
>> a_2 = 'test'
>> c = a_2 + 'toast' # definitely str
>> return typeof(a_2), typeof(b), typeof(c)
>> And this should work better because it allows to infer a_1 as a double
>> and a_2 as a string.
> How would type checks fit into this? Stupid example:
> def test(x):
> if isinstance(x, MyExtType):
> x.call_c_method() # type known, no None check needed
> x.call_py_method() # type unknown, may be None
> Would it work to consider a type checking branch an assignment to a new
> (and differently typed) entry?
No, at least without special handler for this case.
Anyway that's not that hard to implement isinstance() condition may
mark x as being assigned to MyExtType, e.g.:
if isinstance(x, MyExtType):
x = <MyExtType> x # Fake assignment
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