Mypy micro-optimizations (batch 3/3)

[JukkaL]

Several mypy micro-optimizations. Together with batches 1 and 2 these improve self check performance by 1.8%.

This mostly avoids some allocations of nested function objects.

[hauntsaninja]

would _is_subtype = is_proper_subtype if overlap_for_overloads else is_subtype be fast enough since we don't allocate a function object? would be more readable

[ilevkivskyi]

@hauntsaninja That will be still slower because the only way you can an "unknown" Callable is py_call. The idea is to compile those calls into static calls.

[hauntsaninja]

yes it'll be slower, but should be much faster than allocating a new function object while keeping things more readable. don't feel strongly though and i didn't measure

[ilevkivskyi]

One possible way to de-uglify this is to move this whole chunk to a new function outside (say overlap_simple()), and re-use it below. This way it will at least not appear twice.

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅