Hmm, well mypy's support of ParamSpec is still far from perfect, judging by that diff.

I have no idea what those pytype errors mean.

I don't see any obvious issues in how _P is being used here, so the test failure is likely due to a bug in pytype - sorry about that! I'll take a look, but it'll be at least a week before a fix is released, since we're currently in a holiday freeze.

I don't see any obvious issues in how _P is being used here, so the test failure is likely due to a bug in pytype - sorry about that! I'll take a look, but it'll be at least a week before a fix is released, since we're currently in a holiday freeze.

Of course, no worries!!

I've taken out the use of _P for now, so that this is mergeable — the more precise types can always be added later if the pytype/mypy errors are fixed 🙂

Diff from mypy_primer, showing the effect of this PR on open source code:

pyinstrument (https://github.com/joerick/pyinstrument)
- pyinstrument/vendor/decorator.py:295: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[object], None]")
+ pyinstrument/vendor/decorator.py:295: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[..., Iterator[_T_co]], Tuple[Any, ...], Dict[str, Any]], None]")
- pyinstrument/vendor/decorator.py:301: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[object], None]")
+ pyinstrument/vendor/decorator.py:301: error: Incompatible types in assignment (expression has type "Callable[[Any, Any, VarArg(Any), KwArg(Any)], Any]", variable has type "Callable[[_GeneratorContextManager[_T_co], Callable[..., Iterator[_T_co]], Tuple[Any, ...], Dict[str, Any]], None]")

I figured out why pytype was erroring here! The ParamSpec attribute for keyword args is called kwargs, but this PR was using kwds. The next pytype release will change pytype's error message from that weird "Can't find pyi for '_P'" to "Unrecognized ParamSpec attribute: kwds", which I think should be much clearer.

@rchen152 oh wow, I feel like such an idiot 🤦 thanks so much for looking into it!!