diff options
Diffstat (limited to 'dhall_core/src')
| -rw-r--r-- | dhall_core/src/visitor.rs | 195 |
1 files changed, 140 insertions, 55 deletions
diff --git a/dhall_core/src/visitor.rs b/dhall_core/src/visitor.rs index 053932d..dcd860e 100644 --- a/dhall_core/src/visitor.rs +++ b/dhall_core/src/visitor.rs @@ -17,67 +17,49 @@ pub trait GenericVisitor<Input, Return>: Sized { /// time: the visitor itself. The visitor can then carry around multiple closures /// or just one, and Rust is ok with either. See for example TraverseRefVisitor /// and TraverseEmbedVisitor. -pub trait ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>: - Sized -{ +/// This is very generic. For a more legible trait, see ExprFInFallibleVisitor +pub trait ExprFVeryGenericVisitor<'a, Ret, SE1, L1, N1, E1>: Sized { type Error; + type SE2; + type L2; + type N2; + type E2; - fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>; - fn visit_label(&mut self, label: &'a L1) -> Result<L2, Self::Error>; - fn visit_note(self, note: &'a N1) -> Result<N2, Self::Error>; - fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error>; - - fn visit_subexpr_under_binder( - mut self, - _label: &'a L1, + fn visit_subexpr( + &mut self, subexpr: &'a SE1, - ) -> Result<SE2, Self::Error> { - self.visit_subexpr(subexpr) - } + ) -> Result<Self::SE2, Self::Error>; + fn visit_label(&mut self, label: &'a L1) -> Result<Self::L2, Self::Error>; fn visit_binder( - mut self, + self, label: &'a L1, subexpr: &'a SE1, - ) -> Result<(L2, SE2), Self::Error> { - Ok(( - self.visit_label(label)?, - self.visit_subexpr_under_binder(label, subexpr)?, - )) - } + ) -> Result<(Self::L2, Self::SE2), Self::Error>; - fn visit_embed_squash( - self, - embed: &'a E1, - ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { - Ok(ExprF::Embed(self.visit_embed(embed)?)) - } + fn visit_embed_squash(self, embed: &'a E1) -> Result<Ret, Self::Error>; fn visit_note_squash( - mut self, + self, note: &'a N1, subexpr: &'a SE1, - ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { - let subexpr = self.visit_subexpr(subexpr)?; - let note = self.visit_note(note)?; - Ok(ExprF::Note(note, subexpr)) - } + ) -> Result<Ret, Self::Error>; + + // 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<Ret, Self::Error>; } -impl<'a, T, SE1, SE2, L1, L2, N1, N2, E1, E2> - GenericVisitor< - &'a ExprF<SE1, L1, N1, E1>, - Result<ExprF<SE2, L2, N2, E2>, T::Error>, - > for T +impl<'a, T, Ret, SE1, L1, N1, E1> + GenericVisitor<&'a ExprF<SE1, L1, N1, E1>, Result<Ret, T::Error>> for T where L1: Ord, - L2: Ord, - T: ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>, + T::L2: Ord, + T: ExprFVeryGenericVisitor<'a, Ret, SE1, L1, N1, E1>, { - fn visit( - self, - input: &'a ExprF<SE1, L1, N1, E1>, - ) -> Result<ExprF<SE2, L2, N2, E2>, T::Error> { + fn visit(self, input: &'a ExprF<SE1, L1, N1, E1>) -> Result<Ret, T::Error> { fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>( x: &'a [T], f: F, @@ -93,27 +75,27 @@ where None => None, }) } - fn btmap<'a, V, SE, L, N, E, SE2, L2, N2, E2>( + fn btmap<'a, V, Ret, SE, L, N, E>( x: &'a BTreeMap<L, SE>, mut v: V, - ) -> Result<BTreeMap<L2, SE2>, V::Error> + ) -> Result<BTreeMap<V::L2, V::SE2>, V::Error> where L: Ord, - L2: Ord, - V: ExprFFallibleVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>, + V::L2: Ord, + V: ExprFVeryGenericVisitor<'a, Ret, SE, L, N, E>, { x.iter() .map(|(k, x)| Ok((v.visit_label(k)?, v.visit_subexpr(x)?))) .collect() } - fn btoptmap<'a, V, SE, L, N, E, SE2, L2, N2, E2>( + fn btoptmap<'a, V, Ret, SE, L, N, E>( x: &'a BTreeMap<L, Option<SE>>, mut v: V, - ) -> Result<BTreeMap<L2, Option<SE2>>, V::Error> + ) -> Result<BTreeMap<V::L2, Option<V::SE2>>, V::Error> where L: Ord, - L2: Ord, - V: ExprFFallibleVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>, + V::L2: Ord, + V: ExprFVeryGenericVisitor<'a, Ret, SE, L, N, E>, { x.iter() .map(|(k, x)| { @@ -130,7 +112,7 @@ where let mut v = self; use crate::ExprF::*; - Ok(match input { + T::visit_resulting_exprf(match input { Var(V(l, n)) => Var(V(v.visit_label(l)?, *n)), Lam(l, t, e) => { let t = v.visit_subexpr(t)?; @@ -195,12 +177,115 @@ where Projection(e, ls) => { Projection(v.visit_subexpr(e)?, vec(ls, |l| v.visit_label(l))?) } - Note(n, e) => v.visit_note_squash(n, e)?, - Embed(a) => v.visit_embed_squash(a)?, + Note(n, e) => return v.visit_note_squash(n, e), + Embed(a) => return v.visit_embed_squash(a), }) } } +/// Like ExprFVeryGenericVisitor, but sets the return +/// type to ExprF<_> +pub trait ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>: + Sized +{ + type Error; + + fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>; + fn visit_label(&mut self, label: &'a L1) -> Result<L2, Self::Error>; + fn visit_note(self, note: &'a N1) -> Result<N2, Self::Error>; + fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error>; + + fn visit_subexpr_under_binder( + mut self, + _label: &'a L1, + subexpr: &'a SE1, + ) -> Result<SE2, Self::Error> { + self.visit_subexpr(subexpr) + } + + fn visit_binder( + mut self, + label: &'a L1, + subexpr: &'a SE1, + ) -> Result<(L2, SE2), Self::Error> { + Ok(( + self.visit_label(label)?, + self.visit_subexpr_under_binder(label, subexpr)?, + )) + } + + fn visit_embed_squash( + self, + embed: &'a E1, + ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { + Ok(ExprF::Embed(self.visit_embed(embed)?)) + } + + fn visit_note_squash( + mut self, + note: &'a N1, + subexpr: &'a SE1, + ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { + let subexpr = self.visit_subexpr(subexpr)?; + let note = self.visit_note(note)?; + Ok(ExprF::Note(note, subexpr)) + } +} + +impl<'a, T, SE1, SE2, L1, L2, N1, N2, E1, E2> + ExprFVeryGenericVisitor<'a, ExprF<SE2, L2, N2, E2>, SE1, L1, N1, E1> for T +where + T: ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>, +{ + type Error = T::Error; + type SE2 = SE2; + type L2 = L2; + type N2 = N2; + type E2 = E2; + + fn visit_subexpr( + &mut self, + subexpr: &'a SE1, + ) -> Result<Self::SE2, Self::Error> { + self.visit_subexpr(subexpr) + } + + fn visit_label(&mut self, label: &'a L1) -> Result<Self::L2, Self::Error> { + self.visit_label(label) + } + + fn visit_binder( + self, + label: &'a L1, + subexpr: &'a SE1, + ) -> Result<(Self::L2, Self::SE2), Self::Error> { + self.visit_binder(label, subexpr) + } + + fn visit_embed_squash( + self, + embed: &'a E1, + ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { + self.visit_embed_squash(embed) + } + + fn visit_note_squash( + self, + note: &'a N1, + subexpr: &'a SE1, + ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> { + self.visit_note_squash(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<ExprF<SE2, L2, N2, E2>, Self::Error> { + Ok(result) + } +} + /// Like ExprFFallibleVisitor, but without the error handling. pub trait ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>: Sized |