[ty] Make tuple intersection a fallible operation#22094
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charliermarsh merged 1 commit intomainfrom Jan 6, 2026
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Diagnostic diff on typing conformance testsNo changes detected when running ty on typing conformance tests ✅ |
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| let Some(intersected) = builder.intersect(db, &spec) else { | ||
| // The intersection is impossible (e.g., two fixed-length tuples | ||
| // with different lengths). Treat similarly to `Never`. | ||
| return Some(Cow::Owned(TupleSpec::homogeneous(Type::unknown()))); | ||
| }; |
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theoretically this "should" always be Some(), because two tuples cannot have disjoint tuplespecs unless the tuples themselves are disjoint, and two disjoint tuple types cannot coexist in an intersection -- our IntersectionBuilder "should" eagerly simplify an intersection containing disjoint types to Never.
So on that basis, we "should" be able to call .expect() here rather than doing let Some(intersected) = builder.intersect(db, &spec) else {...}.
But I would need to do some work to double-check that we really do uphold those invariants in the ways that we should before I would confidently advise you to change this to a .expect() 😆
For now, it might be worth adding a comment reflecting this
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Summary
This PR attempts to address a TODO in #21965 (comment).