Alternative type checker support

[abelcheung]

Pyre-check

The support for PEP561 is new, so the current situation is still not fully evaluated. However some problems are immediately notable:

• Don't understand re-exported symbols (need to import directly from the file it is defined)
• Thinks logging.LoggerAdapter is a non-generic class
• Fail to import external cssselect annotation

Vendor	Facebook
OS	MacOS, Linux
PEP561 support	Yes (according to facebook/pyre-check#70 )
Max Python target	3.10

PyType

Although not officially supported, typeshed has already been successfully using PyType in test suite by importing pytype.io.parse_pyi.

Vendor	Google
OS	MacOS, Linux
PEP561 support	Hidden (officially no, google/pytype#151 )

PyCharm

Unfortunately the situation is unsatisfactory despite having PEP561 support. There are multiple unfixed issues involving underscored attributes and methods:

• Autocomplete doesn't work for private attributes of base classes
• Autocompletion not works for function_starting with _

Underscored class names like _Element, _ElementTree are building blocks of lxml, which can't be lived without. Annotation of many function arguments become impossible without using them. But the degree of inconvenience introduced by bugs above seriously hinder UX of developers using lxml. It even induced well-intended yet unnecessary PR on types-lxml.

For now, putting to extreme, PyCharm should be avoided like plague until relevant bugs are fixed.

Vendor	JetBrains
OS	Windows, MacOS, Linux
PEP561 support	Yes