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//! TypeVisitor helpers
use crate::{BoundVar, ControlFlow, DebruijnIndex, Interner, TypeVisitable, TypeVisitor};
/// TypeVisitor extensions.
pub trait VisitExt<I: Interner>: TypeVisitable<I> {
/// Check whether there are free (non-bound) variables.
fn has_free_vars(&self, interner: I) -> bool {
let flow = self.visit_with(
&mut FindFreeVarsVisitor { interner },
DebruijnIndex::INNERMOST,
);
matches!(flow, ControlFlow::Break(_))
}
}
impl<T, I: Interner> VisitExt<I> for T where T: TypeVisitable<I> {}
struct FindFreeVarsVisitor<I: Interner> {
interner: I,
}
impl<I: Interner> TypeVisitor<I> for FindFreeVarsVisitor<I> {
type BreakTy = ();
fn as_dyn(&mut self) -> &mut dyn TypeVisitor<I, BreakTy = Self::BreakTy> {
self
}
fn interner(&self) -> I {
self.interner
}
fn visit_free_var(
&mut self,
_bound_var: BoundVar,
_outer_binder: DebruijnIndex,
) -> ControlFlow<()> {
ControlFlow::Break(())
}
}
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