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Diffstat (limited to 'dhall_core/src/visitor.rs')
| -rw-r--r-- | dhall_core/src/visitor.rs | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/dhall_core/src/visitor.rs b/dhall_core/src/visitor.rs new file mode 100644 index 0000000..1b50e46 --- /dev/null +++ b/dhall_core/src/visitor.rs @@ -0,0 +1,226 @@ +use std::collections::BTreeMap; + +use crate::*; + +pub trait ExprVisitor<'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<SE, L, N, E> ExprF<SE, L, N, E> { + pub fn visit<'a, V, SE2, L2, N2, E2>( + &'a self, + mut v: V, + ) -> Result<ExprF<SE2, L2, N2, E2>, V::Error> + where + L: Ord, + L2: Ord, + V: ExprVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>, + { + fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>( + x: &'a Vec<T>, + f: F, + ) -> Result<Vec<U>, Err> { + x.iter().map(f).collect() + } + fn opt<'a, T, U, Err, F: FnOnce(&'a T) -> Result<U, Err>>( + x: &'a Option<T>, + f: F, + ) -> Result<Option<U>, Err> { + Ok(match x { + Some(x) => Some(f(x)?), + None => None, + }) + } + fn btmap<'a, V, SE, L, N, E, SE2, L2, N2, E2>( + x: &'a BTreeMap<L, SE>, + mut v: V, + ) -> Result<BTreeMap<L2, SE2>, V::Error> + where + L: Ord, + L2: Ord, + V: ExprVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>, + { + x.into_iter() + .map(|(k, x)| Ok((v.visit_label(k)?, v.visit_subexpr(x)?))) + .collect() + } + + use crate::ExprF::*; + Ok(match self { + Var(V(l, n)) => Var(V(v.visit_label(l)?, *n)), + Lam(l, t, e) => { + let t = v.visit_subexpr(t)?; + let (l, e) = v.visit_binder(l, e)?; + Lam(l, t, e) + } + Pi(l, t, e) => { + let t = v.visit_subexpr(t)?; + let (l, e) = v.visit_binder(l, e)?; + Pi(l, t, e) + } + Let(l, t, a, e) => { + let t = opt(t, &mut |e| v.visit_subexpr(e))?; + let a = v.visit_subexpr(a)?; + let (l, e) = v.visit_binder(l, e)?; + Let(l, t, a, e) + } + App(f, args) => { + App(v.visit_subexpr(f)?, vec(args, |e| v.visit_subexpr(e))?) + } + Annot(x, t) => Annot(v.visit_subexpr(x)?, v.visit_subexpr(t)?), + Const(k) => Const(*k), + Builtin(v) => Builtin(*v), + BoolLit(b) => BoolLit(*b), + NaturalLit(n) => NaturalLit(*n), + IntegerLit(n) => IntegerLit(*n), + DoubleLit(n) => DoubleLit(*n), + TextLit(t) => TextLit(t.traverse_ref(|e| v.visit_subexpr(e))?), + BinOp(o, x, y) => { + BinOp(*o, v.visit_subexpr(x)?, v.visit_subexpr(y)?) + } + BoolIf(b, t, f) => BoolIf( + v.visit_subexpr(b)?, + v.visit_subexpr(t)?, + v.visit_subexpr(f)?, + ), + EmptyListLit(t) => EmptyListLit(v.visit_subexpr(t)?), + NEListLit(es) => NEListLit(vec(es, |e| v.visit_subexpr(e))?), + EmptyOptionalLit(t) => EmptyOptionalLit(v.visit_subexpr(t)?), + NEOptionalLit(e) => NEOptionalLit(v.visit_subexpr(e)?), + RecordType(kts) => RecordType(btmap(kts, v)?), + RecordLit(kvs) => RecordLit(btmap(kvs, v)?), + UnionType(kts) => UnionType(btmap(kts, v)?), + UnionLit(k, x, kvs) => { + UnionLit(v.visit_label(k)?, v.visit_subexpr(x)?, btmap(kvs, v)?) + } + Merge(x, y, t) => Merge( + v.visit_subexpr(x)?, + v.visit_subexpr(y)?, + opt(t, |e| v.visit_subexpr(e))?, + ), + Field(e, l) => Field(v.visit_subexpr(e)?, v.visit_label(l)?), + 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)?, + }) + } +} + +pub struct TraverseRefVisitor<F1, F2, F3, F4, F5> { + pub visit_subexpr: F1, + pub visit_under_binder: F2, + pub visit_note: F3, + pub visit_embed: F4, + pub visit_label: F5, +} + +impl<'a, SE, L, N, E, SE2, L2, N2, E2, Err, F1, F2, F3, F4, F5> + ExprVisitor<'a, SE, SE2, L, L2, N, N2, E, E2> + for TraverseRefVisitor<F1, F2, F3, F4, F5> +where + SE: 'a, + L: 'a, + N: 'a, + E: 'a, + L: Ord, + L2: Ord, + F1: FnMut(&'a SE) -> Result<SE2, Err>, + F2: FnOnce(&'a L, &'a SE) -> Result<SE2, Err>, + F3: FnOnce(&'a N) -> Result<N2, Err>, + F4: FnOnce(&'a E) -> Result<E2, Err>, + F5: FnMut(&'a L) -> Result<L2, Err>, +{ + type Error = Err; + + fn visit_subexpr(&mut self, subexpr: &'a SE) -> Result<SE2, Self::Error> { + (self.visit_subexpr)(subexpr) + } + fn visit_subexpr_under_binder( + self, + label: &'a L, + subexpr: &'a SE, + ) -> Result<SE2, Self::Error> { + (self.visit_under_binder)(label, subexpr) + } + fn visit_note(self, note: &'a N) -> Result<N2, Self::Error> { + (self.visit_note)(note) + } + fn visit_embed(self, embed: &'a E) -> Result<E2, Self::Error> { + (self.visit_embed)(embed) + } + fn visit_label(&mut self, label: &'a L) -> Result<L2, Self::Error> { + (self.visit_label)(label) + } +} + +pub struct TraverseRefSimpleVisitor<F1> { + pub visit_subexpr: F1, +} + +impl<'a, SE, L, N, E, SE2, Err, F1> ExprVisitor<'a, SE, SE2, L, L, N, N, E, E> + for TraverseRefSimpleVisitor<F1> +where + SE: 'a, + L: Ord + Clone + 'a, + N: Clone + 'a, + E: Clone + 'a, + F1: FnMut(&'a SE) -> Result<SE2, Err>, +{ + type Error = Err; + + fn visit_subexpr(&mut self, subexpr: &'a SE) -> Result<SE2, Self::Error> { + (self.visit_subexpr)(subexpr) + } + fn visit_note(self, note: &'a N) -> Result<N, Self::Error> { + Ok(N::clone(note)) + } + fn visit_embed(self, embed: &'a E) -> Result<E, Self::Error> { + Ok(E::clone(embed)) + } + fn visit_label(&mut self, label: &'a L) -> Result<L, Self::Error> { + Ok(L::clone(label)) + } +} |