[ty] Avoid TypedDict schema cycle for Self fields#25094
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 89.36%. The percentage of expected errors that received a diagnostic held steady at 85.49%. The number of fully passing files held steady at 88/134. |
Memory usage reportMemory usage unchanged ✅ |
|
thejchap
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May 23, 2026
## Summary
`Self` in a class-based `TypedDict` field can cause field annotation
inference to recursively inspect the same `TypedDict` schema while it is
still being collected. This PR makes `TypedDictType::items` cycle-safe
for class-based schemas by using an empty schema as the cycle fallback,
matching the lower-level field collector's recovery behavior.
For example, this no longer panics:
```py
from typing_extensions import Self, TypedDict
class A(TypedDict):
pass
class B(TypedDict):
foo: A | Self
_: B = {}
```
Closes astral-sh/ty#3437.
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Summary
Selfin a class-basedTypedDictfield can cause field annotation inference to recursively inspect the sameTypedDictschema while it is still being collected. This PR makesTypedDictType::itemscycle-safe for class-based schemas by using an empty schema as the cycle fallback, matching the lower-level field collector's recovery behavior.For example, this no longer panics:
Closes astral-sh/ty#3437.