bpo-46553: allow bare typing.ClassVar annotations #30983
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These are used in the wild and covered by dataclasses unit tests. Several static type checkers support this pattern. Note we adjust one test from ClassVar[ClassVar] to ClassVar[ClassVar[int]] so that it still fails. This is surprising, but not a result of weirdness we're doing in this patch. This is a limitation of the current way runtime type checking works that this case is allowed when bare special forms are allowed. For example, before this patch `ClassVar[Final]` is a valid annotation despite nesting these forms being generally disallowed. Addressing this limitation could be future work.
GBeauregard
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GBeauregard
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Jan 28, 2022
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@gvanrossum: Please replace |
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This is a simple matter of just adding
ClassVarto the list of types allowed to be bare before the later call that raises for bare types.These are used in the wild and covered by dataclasses unit tests.
Several static type checkers support this pattern.
Note we adjust one test from
ClassVar[ClassVar]toClassVar[ClassVar[int]]so that it still fails. This is surprising, butnot a result of weirdness we're doing in this patch. This is a
limitation of the current way runtime type checking works that this case
is allowed when bare special forms are allowed. For example, before this
patch
ClassVar[Final]is a valid runtime annotation despite nesting theseforms being generally disallowed, so it's expected allowing bare
ClassVarmakes
ClassVar[ClassVar]valid as well.https://bugs.python.org/issue46553