Don't add strange fictional parameters to the signature of NamedTuple._make()
#15578
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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Interesting! |
Indeed!! |
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Looks like these did actually exist, up until Py3.7. But they were just private early bindings for |
Ahh, thank you! That makes a lot more sense now :) I checked the docs all the way back to 2.6, but only checked the source code and in the REPL on a few recent Python versions. |
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It appears that mypy currently synthesises two fictional parameters for the NamedTuple classmethod
_make():newandlen. I'm not sure why we do this? They've never existed at runtime, and all tests pass if we remove them (except for two that need to be changed slightly, due to the output ofreveal_type(namedtuple_cls._make)changing).It looks like we've been adding these parameters since support for
_make()was first added in 2016: #1810. I can't find any reference in that PR thread about why we add these parameters, however.This PR proposes that we stop adding these parameters, which makes the output of
reveal_type(namedtuple_class._make)much more accurate :)