Almost all i686-linux tests got blocked because of this problem:
https://hydra.nixos.org/eval/1638038#tabs-now-fail
It regressed in PR #105462 (commit ad26cb9ee8).
Now I tested that at least some test got fixed:
nix build -f nixos/release-combined.nix nixos.tests.knot.i686-linux
This change won't even cause any rebuild on 64-bit platforms,
and using nix booleans seems nicer anyway.
Mypy includes mypyc, a compiler that translates annotated Python to C,
which can be compiled into a Python module. When mypy is compiled with
mypyc, it is about 4 times faster than the interpreted mypy, so using
the compiled version is especially useful on large codebases where
typechecking may take a long time.
The wheels distributed on Pypi have included a mypyc-compiled mypy by
default since version 0.700 [1].
[1]: http://mypy-lang.blogspot.com/2019/04/mypy-0700-released-up-to-4x-faster.html
It's not necessary to depend on the "typing" backport since it's in
the standard library; I also observed serious breakage in anything
using the typing module (including) when the backport was in the
closure on >=3.5.
