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fix: Allow instantiation of type[None] in analyze_type_type_callee - #19782
hauntsaninja merged 7 commits into
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Note that this does not fix #19308 (but fortunately the magic comment only affects the first issue, so that's just a plain reference): def get_class(x: int) -> type[str | None]:
if x > 0:
return str
else:
return type(None)
x = get_class(1)
if x is type(None):
print("hi")
else:
reveal_type(x) # N: Revealed type is "type[builtins.str] | type[None]" |
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Thanks for the feedback, @sterliakov! It seems this PR doesn't fix #19308. |
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Very nice!
Along with what's currently there, which ensures NoneType is callable, you should probably assert in your test case that the value produced by NoneType() and friends is None — um, or that its type is type[None], rather (or NoneType). Maybe you can use assert_type for this. Or possibly reveal_type plus expected notices, or some trick about narrowing, if assert_type doesn't work out for some reason.
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@wyattscarpenter Thanks for the review! I've modified the test case to use assert_type to verify the return type, as you suggested. |
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A5rocks
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Thanks. Just one nit on the test you added.
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| def f(n: type[None]): | ||
| assert_type(n(), None) | ||
| def g(n: type[NoneType]): # type: ignore[valid-type] |
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Please use standard test syntax: remove the [out] at the bottom and replace this with a # E: whatever the error was. You can see some more examples around this.
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Diff from mypy_primer, showing the effect of this PR on open source code: sphinx (https://github.com/sphinx-doc/sphinx)
+ sphinx/builders/_epub_base.py:34:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
- sphinx/transforms/post_transforms/code.py:9:1: note: Hint: "python3 -m pip install types-Pygments"
- sphinx/transforms/post_transforms/code.py:9:1: note: (or run "mypy --install-types" to install all missing stub packages)
- sphinx/transforms/post_transforms/code.py:9:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+ sphinx/cmd/build.py:460:1: note: Hint: "python3 -m pip install types-Pygments"
- sphinx/_cli/util/errors.py:102:1: note: Hint: "python3 -m pip install types-Pygments"
- sphinx/_cli/util/errors.py:102:1: note: (or run "mypy --install-types" to install all missing stub packages)
- sphinx/_cli/util/errors.py:102:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+ sphinx/application.py:48:1: note: Hint: "python3 -m pip install types-Pygments"
+ sphinx/application.py:48:1: note: (or run "mypy --install-types" to install all missing stub packages)
scipy-stubs (https://github.com/scipy/scipy-stubs)
+ tests/misc/test_submodules_empty.pyi:3: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
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(Explain how this PR changes mypy.)
Fixes #19660
Allow instantiation of NoneType in type checker
This change fixes the error "Cannot instantiate type 'Type[None]'"
when calling NoneType() or type(None)().
By treating NoneType as a callable that returns None, mypy can now correctly
handle such calls without raising spurious errors.
Also, I added test case testTypeUsingTypeCNoneType covering:
This ensures proper handling of NoneType instantiation and prevents spurious errors.