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-rw-r--r--dhall_core/src/core.rs4
-rw-r--r--dhall_core/src/visitor.rs75
2 files changed, 52 insertions, 27 deletions
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index 7f9fd14..158abe1 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -408,9 +408,8 @@ impl<N, E> Expr<N, E> {
) -> SubExpr<N, E2>
where
N: Clone,
- E2: Clone,
{
- rc(self.visit(&mut visitor::SquashEmbedVisitor(f)))
+ trivial_result(self.visit(&mut visitor::SquashEmbedVisitor(f)))
}
}
@@ -427,7 +426,6 @@ impl<N: Clone> Expr<N, X> {
}
pub fn embed_absurd<E>(&self) -> Expr<N, E> {
self.visit(&mut visitor::EmbedAbsurdVisitor)
- // self.visit(&mut visitor::SquashEmbedVisitor(|e| match *e {}))
}
}
diff --git a/dhall_core/src/visitor.rs b/dhall_core/src/visitor.rs
index dcd860e..c2b0d06 100644
--- a/dhall_core/src/visitor.rs
+++ b/dhall_core/src/visitor.rs
@@ -541,37 +541,64 @@ where
pub struct SquashEmbedVisitor<F1>(pub F1);
-impl<'a, 'b, N, E, E2, F1>
- ExprFInFallibleVisitor<
- 'a,
- SubExpr<N, E>,
- SubExpr<N, E2>,
- Label,
- Label,
- N,
- N,
- E,
- E2,
- > for &'b mut SquashEmbedVisitor<F1>
+impl<'a, 'b, N, E1, E2, F1>
+ ExprFVeryGenericVisitor<'a, SubExpr<N, E2>, SubExpr<N, E1>, Label, N, E1>
+ for &'b mut SquashEmbedVisitor<F1>
where
N: Clone + 'a,
- E2: Clone,
- F1: FnMut(&E) -> SubExpr<N, E2>,
+ F1: FnMut(&E1) -> SubExpr<N, E2>,
{
- fn visit_subexpr(&mut self, subexpr: &'a SubExpr<N, E>) -> SubExpr<N, E2> {
- rc(subexpr.as_ref().visit(&mut **self))
+ type Error = X;
+ type SE2 = SubExpr<N, E2>;
+ type L2 = Label;
+ type N2 = N;
+ type E2 = E2;
+
+ fn visit_subexpr(
+ &mut self,
+ subexpr: &'a SubExpr<N, E1>,
+ ) -> Result<Self::SE2, Self::Error> {
+ Ok(subexpr.as_ref().visit(&mut **self)?)
}
- fn visit_note(self, note: &'a N) -> N {
- N::clone(note)
+
+ fn visit_label(
+ &mut self,
+ label: &'a Label,
+ ) -> Result<Self::L2, Self::Error> {
+ Ok(Label::clone(label))
}
- fn visit_embed(self, _: &'a E) -> E2 {
- unreachable!()
+
+ fn visit_binder(
+ mut self,
+ label: &'a Label,
+ subexpr: &'a SubExpr<N, E1>,
+ ) -> Result<(Self::L2, Self::SE2), Self::Error> {
+ Ok((self.visit_label(label)?, self.visit_subexpr(subexpr)?))
}
- fn visit_embed_squash(self, embed: &'a E) -> Expr<N, E2> {
- (self.0)(embed).unroll()
+
+ fn visit_embed_squash(
+ self,
+ embed: &'a E1,
+ ) -> Result<SubExpr<N, E2>, Self::Error> {
+ Ok((self.0)(embed))
}
- fn visit_label(&mut self, label: &'a Label) -> Label {
- Label::clone(label)
+
+ fn visit_note_squash(
+ mut self,
+ note: &'a N,
+ subexpr: &'a SubExpr<N, E1>,
+ ) -> Result<SubExpr<N, E2>, Self::Error> {
+ let subexpr = self.visit_subexpr(subexpr)?;
+ let note = N::clone(note);
+ Ok(rc(ExprF::Note(note, subexpr)))
+ }
+
+ // Called with the result of the map, in the non-embed/note case.
+ // Useful to change the result type, and/or avoid some loss of info
+ fn visit_resulting_exprf(
+ result: ExprF<Self::SE2, Self::L2, Self::N2, Self::E2>,
+ ) -> Result<SubExpr<N, E2>, Self::Error> {
+ Ok(rc(result))
}
}