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[ty] Prevent tainted loop bindings in cycle normalization #24143

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Merged
ibraheemdev merged 1 commit into from
Mar 23, 2026
Merged

[ty] Prevent tainted loop bindings in cycle normalization #24143

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3 changes: 1 addition & 2 deletions crates/ty_python_semantic/resources/mdtest/loops/while_loop.md
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Original file line number Diff line number Diff line change
Expand Up @@ -477,8 +477,7 @@ def random() -> bool:

x = 0
while random():
# TODO: This should reveal `Literal[0]`.
reveal_type(x) # revealed: Literal[0, 2]
reveal_type(x) # revealed: Literal[0]
if x == 1:
x = 2
```
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16 changes: 11 additions & 5 deletions crates/ty_python_semantic/src/place.rs
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Expand Up @@ -1159,12 +1159,12 @@ pub(crate) fn loop_header_reachability<'db>(

fn loop_header_reachability_cycle_recover<'db>(
_db: &'db dyn Db,
_cycle: &salsa::Cycle,
cycle: &salsa::Cycle,
previous: &LoopHeaderReachability<'db>,
result: LoopHeaderReachability<'db>,
_definition: Definition<'db>,
) -> LoopHeaderReachability<'db> {
result.cycle_normalized(previous)
result.cycle_normalized(previous, cycle)
}

fn loop_header_reachability_impl<'db>(
Expand Down Expand Up @@ -1236,10 +1236,16 @@ impl<'db> LoopHeaderReachability<'db> {
fn cycle_normalized(
self,
previous: &LoopHeaderReachability<'db>,
cycle: &salsa::Cycle,
) -> LoopHeaderReachability<'db> {
let mut reachable_bindings = FxIndexSet::default();
reachable_bindings.extend(previous.reachable_bindings.iter().copied());
reachable_bindings.extend(self.reachable_bindings);
// Avoid losing precision for cycles that are soon to converge.
// See [`Type::cycle_normalized`] for more details.
let reachable_bindings = if cycle.iteration() <= 1 {
self.reachable_bindings
} else {
let previous_bindings = previous.reachable_bindings.iter().copied();
previous_bindings.chain(self.reachable_bindings).collect()
};

LoopHeaderReachability {
deleted_reachability: self.deleted_reachability,
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