diff options
Diffstat (limited to '')
| -rw-r--r-- | dhall/src/syntax/ast/expr.rs | 4 | ||||
| -rw-r--r-- | dhall/src/syntax/ast/visitor.rs | 220 |
2 files changed, 84 insertions, 140 deletions
diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs index 722630f..512010a 100644 --- a/dhall/src/syntax/ast/expr.rs +++ b/dhall/src/syntax/ast/expr.rs @@ -1,5 +1,5 @@ use crate::syntax::map::{DupTreeMap, DupTreeSet}; -use crate::syntax::visitor::{self, ExprKindVisitor}; +use crate::syntax::visitor; use crate::syntax::*; pub type Integer = isize; @@ -176,7 +176,7 @@ impl<SE> ExprKind<SE> { &'a self, visit: impl FnMut(Option<&'a Label>, &'a SE) -> Result<SE2, Err>, ) -> Result<ExprKind<SE2>, Err> { - visitor::TraverseRefMaybeBinderVisitor(visit).visit(self) + visitor::visit_ref(self, visit) } pub fn traverse_ref_with_special_handling_of_binders<'a, SE2, Err>( diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs index fc90efd..39959ac 100644 --- a/dhall/src/syntax/ast/visitor.rs +++ b/dhall/src/syntax/ast/visitor.rs @@ -2,171 +2,115 @@ use std::iter::FromIterator; use crate::syntax::*; -/// A visitor trait that can be used to traverse `ExprKind`s. We need this pattern so that Rust lets -/// us have as much mutability as we can. -/// For example, `traverse_ref_with_special_handling_of_binders` cannot be made using only -/// `traverse_ref`, because `traverse_ref` takes a `FnMut` so we would need to pass multiple -/// mutable reverences to this argument to `traverse_ref`. But Rust's ownership system is all about -/// preventing exactly this ! So we have to be more clever. The visitor pattern allows us to have -/// only one mutable thing the whole 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. -pub trait ExprKindVisitor<'a, SE1, SE2>: Sized { - type Error; +fn vec<'a, T, U, Err>( + x: &'a [T], + f: impl FnMut(&'a T) -> Result<U, Err>, +) -> Result<Vec<U>, Err> { + x.iter().map(f).collect() +} - fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>; +fn opt<'a, T, U, Err>( + x: &'a Option<T>, + f: impl FnOnce(&'a T) -> Result<U, Err>, +) -> Result<Option<U>, Err> { + Ok(match x { + Some(x) => Some(f(x)?), + None => None, + }) +} - fn visit_subexpr_under_binder( - mut self, - _label: &'a Label, - subexpr: &'a SE1, - ) -> Result<SE2, Self::Error> { - self.visit_subexpr(subexpr) - } +fn dupmap<'a, SE1, SE2, T, Err>( + x: impl IntoIterator<Item = (&'a Label, &'a SE1)>, + mut f: impl FnMut(&'a SE1) -> Result<SE2, Err>, +) -> Result<T, Err> +where + SE1: 'a, + T: FromIterator<(Label, SE2)>, +{ + x.into_iter().map(|(k, x)| Ok((k.clone(), f(x)?))).collect() +} - fn visit( - self, - input: &'a ExprKind<SE1>, - ) -> Result<ExprKind<SE2>, Self::Error> { - visit_ref(self, input) - } +fn optdupmap<'a, SE1, SE2, T, Err>( + x: impl IntoIterator<Item = (&'a Label, &'a Option<SE1>)>, + mut f: impl FnMut(&'a SE1) -> Result<SE2, Err>, +) -> Result<T, Err> +where + SE1: 'a, + T: FromIterator<(Label, Option<SE2>)>, +{ + x.into_iter() + .map(|(k, x)| { + Ok(( + k.clone(), + match x { + Some(x) => Some(f(x)?), + None => None, + }, + )) + }) + .collect() } -fn visit_ref<'a, V, SE1, SE2>( - mut v: V, +pub(crate) fn visit_ref<'a, F, SE1, SE2, Err>( input: &'a ExprKind<SE1>, -) -> Result<ExprKind<SE2>, V::Error> + mut f: F, +) -> Result<ExprKind<SE2>, Err> where - V: ExprKindVisitor<'a, SE1, SE2>, + F: FnMut(Option<&'a Label>, &'a SE1) -> Result<SE2, Err>, { - fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>( - x: &'a [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 dupmap<'a, V, SE1, SE2, T>( - x: impl IntoIterator<Item = (&'a Label, &'a SE1)>, - mut v: V, - ) -> Result<T, V::Error> - where - SE1: 'a, - T: FromIterator<(Label, SE2)>, - V: ExprKindVisitor<'a, SE1, SE2>, - { - x.into_iter() - .map(|(k, x)| Ok((k.clone(), v.visit_subexpr(x)?))) - .collect() - } - fn optdupmap<'a, V, SE1, SE2, T>( - x: impl IntoIterator<Item = (&'a Label, &'a Option<SE1>)>, - mut v: V, - ) -> Result<T, V::Error> - where - SE1: 'a, - T: FromIterator<(Label, Option<SE2>)>, - V: ExprKindVisitor<'a, SE1, SE2>, - { - x.into_iter() - .map(|(k, x)| { - Ok(( - k.clone(), - match x { - Some(x) => Some(v.visit_subexpr(x)?), - None => None, - }, - )) - }) - .collect() + // Can't use closures because of borrowing rules + macro_rules! expr { + ($e:expr) => { + f(None, $e) + }; + ($l:expr, $e:expr) => { + f(Some($l), $e) + }; } use crate::syntax::ExprKind::*; Ok(match input { Var(v) => Var(v.clone()), Lam(l, t, e) => { - let t = v.visit_subexpr(t)?; - let e = v.visit_subexpr_under_binder(l, e)?; + let t = expr!(t)?; + let e = expr!(l, e)?; Lam(l.clone(), t, e) } Pi(l, t, e) => { - let t = v.visit_subexpr(t)?; - let e = v.visit_subexpr_under_binder(l, e)?; + let t = expr!(t)?; + let e = expr!(l, e)?; Pi(l.clone(), t, e) } Let(l, t, a, e) => { - let t = opt(t, &mut |e| v.visit_subexpr(e))?; - let a = v.visit_subexpr(a)?; - let e = v.visit_subexpr_under_binder(l, e)?; + let t = opt(t, &mut |e| expr!(e))?; + let a = expr!(a)?; + let e = expr!(l, e)?; Let(l.clone(), t, a, e) } - App(f, a) => App(v.visit_subexpr(f)?, v.visit_subexpr(a)?), - Annot(x, t) => Annot(v.visit_subexpr(x)?, v.visit_subexpr(t)?), + App(f, a) => App(expr!(f)?, expr!(a)?), + Annot(x, t) => Annot(expr!(x)?, expr!(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))?), - SomeLit(e) => SomeLit(v.visit_subexpr(e)?), - RecordType(kts) => RecordType(dupmap(kts, v)?), - RecordLit(kvs) => RecordLit(dupmap(kvs, v)?), - UnionType(kts) => UnionType(optdupmap(kts, v)?), - Merge(x, y, t) => Merge( - v.visit_subexpr(x)?, - v.visit_subexpr(y)?, - opt(t, |e| v.visit_subexpr(e))?, - ), - ToMap(x, t) => { - ToMap(v.visit_subexpr(x)?, opt(t, |e| v.visit_subexpr(e))?) - } - Field(e, l) => Field(v.visit_subexpr(e)?, l.clone()), - Projection(e, ls) => Projection(v.visit_subexpr(e)?, ls.clone()), - ProjectionByExpr(e, x) => { - ProjectionByExpr(v.visit_subexpr(e)?, v.visit_subexpr(x)?) - } - Completion(e, x) => { - Completion(v.visit_subexpr(e)?, v.visit_subexpr(x)?) - } - Assert(e) => Assert(v.visit_subexpr(e)?), - Import(i) => Import(i.traverse_ref(|e| v.visit_subexpr(e))?), + TextLit(t) => TextLit(t.traverse_ref(|e| expr!(e))?), + BinOp(o, x, y) => BinOp(*o, expr!(x)?, expr!(y)?), + BoolIf(b, t, f) => BoolIf(expr!(b)?, expr!(t)?, expr!(f)?), + EmptyListLit(t) => EmptyListLit(expr!(t)?), + NEListLit(es) => NEListLit(vec(es, |e| expr!(e))?), + SomeLit(e) => SomeLit(expr!(e)?), + RecordType(kts) => RecordType(dupmap(kts, |e| expr!(e))?), + RecordLit(kvs) => RecordLit(dupmap(kvs, |e| expr!(e))?), + UnionType(kts) => UnionType(optdupmap(kts, |e| expr!(e))?), + Merge(x, y, t) => Merge(expr!(x)?, expr!(y)?, opt(t, |e| expr!(e))?), + ToMap(x, t) => ToMap(expr!(x)?, opt(t, |e| expr!(e))?), + Field(e, l) => Field(expr!(e)?, l.clone()), + Projection(e, ls) => Projection(expr!(e)?, ls.clone()), + ProjectionByExpr(e, x) => ProjectionByExpr(expr!(e)?, expr!(x)?), + Completion(e, x) => Completion(expr!(e)?, expr!(x)?), + Assert(e) => Assert(expr!(e)?), + Import(i) => Import(i.traverse_ref(|e| expr!(e))?), }) } - -pub struct TraverseRefMaybeBinderVisitor<F>(pub F); - -impl<'a, SE, SE2, Err, F> ExprKindVisitor<'a, SE, SE2> - for TraverseRefMaybeBinderVisitor<F> -where - SE: 'a, - F: FnMut(Option<&'a Label>, &'a SE) -> Result<SE2, Err>, -{ - type Error = Err; - - fn visit_subexpr(&mut self, subexpr: &'a SE) -> Result<SE2, Self::Error> { - (self.0)(None, subexpr) - } - fn visit_subexpr_under_binder( - mut self, - label: &'a Label, - subexpr: &'a SE, - ) -> Result<SE2, Self::Error> { - (self.0)(Some(label), subexpr) - } -} |