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Prohibit parameterized generics in isinstance #3037

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pkch opened this issue Mar 20, 2017 · 1 comment
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Prohibit parameterized generics in isinstance #3037

pkch opened this issue Mar 20, 2017 · 1 comment
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@pkch
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pkch commented Mar 20, 2017

As @ilevkivskyi commented (#3005 (comment)), it would be nice to fail type check on this code:

obj = 1
if isinstance(obj, Iterable[int]):
    1

because it fails in runtime with TypeError.

I can easily see this situation inside checker.py:get_isinstance_type() by verifying that len(type.items()[0].ret_type.args) == 0; but is it the right place to message about type validation problems?
@pkch pkch mentioned this issue Mar 20, 2017
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@ilevkivskyi
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Maybe the right place is in visit_call_expr in checkexpr.py? If the name of function called is builtins.isinstance or builtins.issubclass and there is, for example, any CallableType argument with .is_class_obj() returning True and having type arguments, then you issue a warning.

@pkch pkch mentioned this issue Mar 21, 2017
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@elazarg elazarg mentioned this issue Apr 3, 2017
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