Replace mypy_run.py hack with patched mypy version proposed for upstream inclusion

Author: ntninja

datastore/core/objectstore.py

@@ -26,7 +26,7 @@ def is_valid_value_type(value: util.stream.ArbitraryReceiveChannel[typing.Any])
 	Unfortunately this cannot check whether iterators return the correct types,
 	so the utility of this function unfortunately is limited to some extent.
 	"""
-	return isinstance(value, (  # type: ignore[misc]  # “Should be always true…”
+	return isinstance(value, (  # type: ignore[unreachable]  # “Should be always true…”
 		trio.abc.ReceiveChannel,
 		collections.abc.AsyncIterable,
 		collections.abc.Awaitable,

mypy_run.py

@@ -6,13 +6,13 @@ envlist =
 	styleck
 
 # While tox does have PEP-517 (pyproject.toml buildapi) support it's very
-# inconvinient and slow to use so disable installation of ourselves entirely
+# inconvenient and slow to use so disable installation of ourselves entirely
 skipsdist = true
 
 # Keep this in sync with `tool.flit.metadata.requires` from "pyproject.toml"
 #
 # Note the difference in version number strictness is intentional however since
-# 0.13.0 fixes an annoying test warining.
+# 0.13.0 fixes an annoying test warning.
 deps =
 	trio ~= 0.13.0
 
@@ -39,19 +39,15 @@ commands =
 skip_install = true
 deps =
 	{[tox]deps}
-	mypy   >= 0.761
 	pytest ~= 5.0
+	git+https://github.com/alexander255/mypy.git@0cf7515eefd981bd7627a371dd109f1a4cddc90f
 commands =
-	python {toxinidir}/mypy_run.py --config-file=tox.ini {posargs} -p datastore -p tests
+	mypy --config-file=tox.ini {posargs} -p datastore -p tests
 
 # Pass down TERM environment variable to allow mypy output to be colorized
 # See: https://github.com/tox-dev/tox/issues/1441
 passenv = TERM
 
-#HACK: We cannot use mypy's optimized (mypyc) binary distribution as that breaks
-#      the monkey patching in the `./mypy_run.py` script…
-install_command=python -m pip install --no-binary mypy {opts} {packages}
-
 [mypy]
 # CLI behaviour
 color_output     = true
@@ -78,6 +74,8 @@ warn_unused_ignores  = true
 warn_return_any      = true
 warn_unreachable     = true
 
+pep561_override = pytest, trio
+
 [mypy-datastore.core.query]
 #FIXME: This file is seriously messed up
 ignore_errors = true