[ty] Respect dict-compatible fallbacks in TypedDict unions#25242
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Memory usage reportMemory usage unchanged ✅ |
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. |
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-key |
0 | 4 | 0 |
missing-typed-dict-key |
0 | 2 | 0 |
unused-type-ignore-comment |
1 | 0 | 0 |
| Total | 1 | 6 | 0 |
Raw diff:
hydra-zen (https://github.com/mit-ll-responsible-ai/hydra-zen)
- tests/annotations/declarations.py:366:59 error[invalid-key] Unknown key "a" for TypedDict `EmptyDict`
- tests/annotations/declarations.py:366:72 error[invalid-key] Unknown key "a" for TypedDict `EmptyDict`
+ tests/annotations/declarations.py:405:32 warning[unused-type-ignore-comment] Unused blanket `type: ignore` directive
pandas-stubs (https://github.com/pandas-dev/pandas-stubs)
- tests/frame/test_frame.py:3293:34 error[missing-typed-dict-key] Missing required key 'formats' in TypedDict `_DTypeDict` constructor
- tests/frame/test_frame.py:3293:34 error[missing-typed-dict-key] Missing required key 'names' in TypedDict `_DTypeDict` constructor
- tests/frame/test_frame.py:3293:35 error[invalid-key] Unknown key "col1" for TypedDict `_DTypeDict`
- tests/frame/test_frame.py:3293:52 error[invalid-key] Unknown key "col2" for TypedDict `_DTypeDict`6f2963f to
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dict-compatible fallbacks in TypedDict unions
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AlexWaygood
reviewed
May 20, 2026
| has_dict_compatible_fallback = true; | ||
| } else if !has_dict_compatible_fallback | ||
| && dict_fallback.is_assignable_to(self.db(), element) | ||
| && element.is_assignable_to(self.db(), mapping_fallback) |
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it's not clear to me why we're imposing the restriction here that the element needs to be assignable to Mapping[Unknown, Unknown] in order for it to be a valid dict-compatible fallback. On your branch, we still emit a false-positive error here (it's a false positive because dict[int, int] is a subtype of Iterable[int]):
from typing import TypedDict, Iterable
class Foo(TypedDict):
x: int
def f(obj: Foo | Iterable[int]): ...
f({42: 42})
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This is clearly an improvement but not sufficiently general, lemme think.
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Ah, ok, I think the speculative inference piece on its own is sufficient now.
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thejchap
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to thejchap/ruff
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May 23, 2026
…sh#25242) ## Summary Prior to this change, this snippet would produce a TypedDict-based `missing-key` diagnostic, because the RHS wasn't viewed as assignable to the `Mapping[int, float]` (since we were only gating on `dict`): ```py from typing import TypedDict, Mapping class Foo(TypedDict): some: str name: str mapping: Foo | Mapping[int, float] = {1: 5.2} ``` We now use speculative inference to determine whether the non-TypedDict union member `T` is a viable fallback type. Closes astral-sh/ty#3488.
anishgirianish
pushed a commit
to anishgirianish/ruff
that referenced
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May 28, 2026
…sh#25242) ## Summary Prior to this change, this snippet would produce a TypedDict-based `missing-key` diagnostic, because the RHS wasn't viewed as assignable to the `Mapping[int, float]` (since we were only gating on `dict`): ```py from typing import TypedDict, Mapping class Foo(TypedDict): some: str name: str mapping: Foo | Mapping[int, float] = {1: 5.2} ``` We now use speculative inference to determine whether the non-TypedDict union member `T` is a viable fallback type. Closes astral-sh/ty#3488.
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Summary
Prior to this change, this snippet would produce a TypedDict-based
missing-keydiagnostic, because the RHS wasn't viewed as assignable to theMapping[int, float](since we were only gating ondict):We now use speculative inference to determine whether the non-TypedDict union member
Tis a viable fallback type.Closes astral-sh/ty#3488.