[ty] use interior mutability in type visitors#19871
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Diagnostic diff on typing conformance testsNo changes detected when running ty on typing conformance tests ✅ |
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AlexWaygood
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## Summary After #19871, I realized that now that we are passing around shared references to `CycleDetector` visitors, we can now also simplify the `visit` callback signature; we don't need to smuggle a single visitor reference through it anymore. This is a pretty minor simplification, and it doesn't really make anything shorter since I typically used a very short name (`v`) for the smuggled reference, but I think it reduces cognitive overhead in reading these `visit` usages; the extra variable would likely be confusing otherwise for a reader. ## Test Plan Existing CI.
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* main: Don't cache files with diagnostics (#19869) [ty] support recursive type aliases (#19805) [ty] Remove unsafe `salsa::Update` implementations in `tuple.rs` (#19880) [ty] Function argument inlay hints (#19269) [ty] Remove Salsa interning for `TypedDictType` (#19879) Fix `lint.future-annotations` link (#19876) [ty] Reduce memory usage of `TupleSpec` and `TupleType` (#19872) [ty] Track heap usage of salsa structs (#19790) Update salsa to pull in tracked struct changes (#19843) [ty] simplify CycleDetector::visit signature (#19873) [ty] use interior mutability in type visitors (#19871) [ty] Fix tool name is None when no ty path is given in ty_benchmark (#19870) [ty] Remove `Type::Tuple` (#19669) [ty] Short circuit `ReachabilityConstraints::analyze_single` for dynamic types (#19867)
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Summary
Type visitors are conceptually immutable, they just internally track the types they've seen (and some maintain a cache of results.) Passing around mutable visitors everywhere can get us into borrow-checker trouble in some cases, where we need to recursively pass along the visitor inside more than one closure with non-disjoint lifetime.
Use interior mutability (via
RefCellandCell) inside the visitors instead, to allow us to pass around shared references.Test Plan
Existing tests.