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## Summary We have the ability to defer type inference of some parts of definitions, so as to allow us to create a type that may need to be recursively referenced in those other parts of the definition. We also have the ability to do type inference in a context where all name resolution should be deferred (that is, names should be looked up from all-reachable-definitions rather than from the location of use.) This is used for all annotations in stubs, or if `from __future__ import annotations` is active. Previous to this PR, these two concepts were linked: deferred-inference always implied deferred-name-resolution, though we also supported deferred-name-resolution without deferred-inference, via `DeferredExpressionState`. For the upcoming `typing.TypeAlias` support, I will defer inference of the entire RHS of the alias (so as to support cycles), but that doesn't imply deferred name resolution; at runtime, the RHS of a name annotated as `typing.TypeAlias` is executed eagerly. So this PR fully de-couples the two concepts, instead explicitly setting the `DeferredExpressionState` in those cases where we should defer name resolution. It also fixes a long-standing related bug, where we were deferring name resolution of all names in class bases, if any of the class bases contained a stringified annotation. ## Test Plan Added test that failed before this PR.
460 B
460 B
Class definitions
Deferred resolution of bases
Only the stringified name is deferred
If a class base contains a stringified name, only that name is deferred. Other names are resolved normally.
[environment]
python-version = "3.12"
A = int
class G[T]: ...
class C(A, G["B"]): ...
A = str
B = bytes
reveal_type(C.__mro__) # revealed: tuple[<class 'C'>, <class 'int'>, <class 'G[bytes]'>, typing.Generic, <class 'object'>]