[ty] Preserve constrained TypeVar identity in narrowing intersections#23850
Merged
charliermarsh merged 1 commit intomainfrom Mar 10, 2026
Merged
[ty] Preserve constrained TypeVar identity in narrowing intersections#23850charliermarsh merged 1 commit intomainfrom
charliermarsh merged 1 commit intomainfrom
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 85.05%. The percentage of expected errors that received a diagnostic held steady at 78.05%. The number of fully passing files held steady at 63/132. |
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Memory usage reportSummary
Significant changesClick to expand detailed breakdownprefect
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charliermarsh
commented
Mar 10, 2026
| def f[T: (P, Q)](t: T) -> None: | ||
| if isinstance(t, P): | ||
| reveal_type(t) # revealed: P | ||
| reveal_type(t) # revealed: T@f & P |
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Author
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These look like regressions but I think they might be correct?
Given:
class P:
def p(self) -> None: ...
class Q:
def q(self) -> None: ...
class Both(P, Q):
pass
def f[T: (P, Q)](t: T) -> T:
if isinstance(t, P):
reveal_type(t) # revealed: T@f & P
t.p()
return t
else:
reveal_type(t) # revealed: Q & ~P
t.q()
return t
def takes_q(x: Q) -> Q:
return f(x)
both = Both()
q: Q = takes_q(both) # valid; runtime goes into the `if` branch
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| Lint rule | Added | Removed | Changed |
|---|---|---|---|
invalid-await |
0 | 40 | 0 |
invalid-assignment |
0 | 24 | 0 |
invalid-return-type |
0 | 17 | 3 |
no-matching-overload |
0 | 7 | 0 |
invalid-argument-type |
2 | 3 | 0 |
possibly-missing-attribute |
0 | 4 | 0 |
| Total | 2 | 95 | 3 |
f349ff1 to
e91cf6c
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Member
Author
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I understand the spirit of this change but I'm not familiar with the implementation here. The ecosystem diagnostics do look like false positives being removed, though. |
dcreager
approved these changes
Mar 10, 2026
| def f[T: (P, Q)](t: T) -> None: | ||
| if isinstance(t, P): | ||
| reveal_type(t) # revealed: P | ||
| reveal_type(t) # revealed: T@f & P |
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Summary
Closes astral-sh/ty#2782.