Rename syntax::core to syntax::ast

8 files changed, 0 insertions, 1569 deletions

diff --git a/dhall/src/syntax/core/expr.rs b/dhall/src/syntax/core/expr.rs
deleted file mode 100644
index 5b9f401..0000000
--- a/dhall/src/syntax/core/expr.rs
+++ /dev/null
@@ -1,377 +0,0 @@
-use crate::syntax::map::{DupTreeMap, DupTreeSet};
-use crate::syntax::visitor::{self, ExprFMutVisitor, ExprFVisitor};
-use crate::syntax::*;
-
-pub type Integer = isize;
-pub type Natural = usize;
-pub type Double = NaiveDouble;
-
-pub fn trivial_result<T>(x: Result<T, !>) -> T {
-    match x {
-        Ok(x) => x,
-        Err(e) => e,
-    }
-}
-
-/// Double with bitwise equality
-#[derive(Debug, Copy, Clone)]
-pub struct NaiveDouble(f64);
-
-impl PartialEq for NaiveDouble {
-    fn eq(&self, other: &Self) -> bool {
-        self.0.to_bits() == other.0.to_bits()
-    }
-}
-
-impl Eq for NaiveDouble {}
-
-impl std::hash::Hash for NaiveDouble {
-    fn hash<H>(&self, state: &mut H)
-    where
-        H: std::hash::Hasher,
-    {
-        self.0.to_bits().hash(state)
-    }
-}
-
-impl From<f64> for NaiveDouble {
-    fn from(x: f64) -> Self {
-        NaiveDouble(x)
-    }
-}
-
-impl From<NaiveDouble> for f64 {
-    fn from(x: NaiveDouble) -> f64 {
-        x.0
-    }
-}
-
-/// Constants for a pure type system
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum Const {
-    Type,
-    Kind,
-    Sort,
-}
-
-/// Bound variable
-///
-/// The `Label` field is the variable's name (i.e. \"`x`\").
-/// The `Int` field is a DeBruijn index.
-/// See dhall-lang/standard/semantics.md for details
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct V<Label>(pub Label, pub usize);
-
-// This is only for the specific `Label` type, not generic
-impl From<Label> for V<Label> {
-    fn from(x: Label) -> V<Label> {
-        V(x, 0)
-    }
-}
-impl<'a> From<&'a Label> for V<Label> {
-    fn from(x: &'a Label) -> V<Label> {
-        V(x.clone(), 0)
-    }
-}
-
-// Definition order must match precedence order for
-// pretty-printing to work correctly
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub enum BinOp {
-    /// `x ? y`
-    ImportAlt,
-    /// `x || y`
-    BoolOr,
-    /// `x + y`
-    NaturalPlus,
-    /// `x ++ y`
-    TextAppend,
-    /// `x # y`
-    ListAppend,
-    /// `x && y`
-    BoolAnd,
-    /// `x ∧ y`
-    RecursiveRecordMerge,
-    /// `x ⫽ y`
-    RightBiasedRecordMerge,
-    /// `x ⩓ y`
-    RecursiveRecordTypeMerge,
-    /// `x * y`
-    NaturalTimes,
-    /// `x == y`
-    BoolEQ,
-    /// `x != y`
-    BoolNE,
-    /// x === y
-    Equivalence,
-}
-
-/// Built-ins
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-pub enum Builtin {
-    Bool,
-    Natural,
-    Integer,
-    Double,
-    Text,
-    List,
-    Optional,
-    OptionalNone,
-    NaturalBuild,
-    NaturalFold,
-    NaturalIsZero,
-    NaturalEven,
-    NaturalOdd,
-    NaturalToInteger,
-    NaturalShow,
-    NaturalSubtract,
-    IntegerToDouble,
-    IntegerShow,
-    DoubleShow,
-    ListBuild,
-    ListFold,
-    ListLength,
-    ListHead,
-    ListLast,
-    ListIndexed,
-    ListReverse,
-    OptionalFold,
-    OptionalBuild,
-    TextShow,
-}
-
-// Each node carries an annotation.
-#[derive(Debug, Clone)]
-pub struct Expr<Embed>(Box<(RawExpr<Embed>, Span)>);
-
-pub type RawExpr<Embed> = ExprF<Expr<Embed>, Embed>;
-
-impl<Embed: PartialEq> std::cmp::PartialEq for Expr<Embed> {
-    fn eq(&self, other: &Self) -> bool {
-        self.0.as_ref().0 == other.0.as_ref().0
-    }
-}
-
-impl<Embed: Eq> std::cmp::Eq for Expr<Embed> {}
-
-impl<Embed: std::hash::Hash> std::hash::Hash for Expr<Embed> {
-    fn hash<H>(&self, state: &mut H)
-    where
-        H: std::hash::Hasher,
-    {
-        (self.0).0.hash(state)
-    }
-}
-
-/// Syntax tree for expressions
-// Having the recursion out of the enum definition enables writing
-// much more generic code and improves pattern-matching behind
-// smart pointers.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum ExprF<SubExpr, Embed> {
-    Const(Const),
-    ///  `x`
-    ///  `x@n`
-    Var(V<Label>),
-    ///  `λ(x : A) -> b`
-    Lam(Label, SubExpr, SubExpr),
-    ///  `A -> B`
-    ///  `∀(x : A) -> B`
-    Pi(Label, SubExpr, SubExpr),
-    ///  `f a`
-    App(SubExpr, SubExpr),
-    ///  `let x     = r in e`
-    ///  `let x : t = r in e`
-    Let(Label, Option<SubExpr>, SubExpr, SubExpr),
-    ///  `x : t`
-    Annot(SubExpr, SubExpr),
-    ///  `assert : t`
-    Assert(SubExpr),
-    /// Built-in values
-    Builtin(Builtin),
-    // Binary operations
-    BinOp(BinOp, SubExpr, SubExpr),
-    ///  `True`
-    BoolLit(bool),
-    ///  `if x then y else z`
-    BoolIf(SubExpr, SubExpr, SubExpr),
-    ///  `1`
-    NaturalLit(Natural),
-    ///  `+2`
-    IntegerLit(Integer),
-    ///  `3.24`
-    DoubleLit(Double),
-    ///  `"Some ${interpolated} text"`
-    TextLit(InterpolatedText<SubExpr>),
-    ///  `[] : t`
-    EmptyListLit(SubExpr),
-    ///  `[x, y, z]`
-    NEListLit(Vec<SubExpr>),
-    ///  `Some e`
-    SomeLit(SubExpr),
-    ///  `{ k1 : t1, k2 : t1 }`
-    RecordType(DupTreeMap<Label, SubExpr>),
-    ///  `{ k1 = v1, k2 = v2 }`
-    RecordLit(DupTreeMap<Label, SubExpr>),
-    ///  `< k1 : t1, k2 >`
-    UnionType(DupTreeMap<Label, Option<SubExpr>>),
-    ///  `merge x y : t`
-    Merge(SubExpr, SubExpr, Option<SubExpr>),
-    ///  `toMap x : t`
-    ToMap(SubExpr, Option<SubExpr>),
-    ///  `e.x`
-    Field(SubExpr, Label),
-    ///  `e.{ x, y, z }`
-    Projection(SubExpr, DupTreeSet<Label>),
-    ///  `e.(t)`
-    ProjectionByExpr(SubExpr, SubExpr),
-    /// `./some/path`
-    Import(Import<SubExpr>),
-    /// Embeds the result of resolving an import
-    Embed(Embed),
-}
-
-impl<SE, E> ExprF<SE, E> {
-    pub fn traverse_ref_with_special_handling_of_binders<'a, SE2, Err>(
-        &'a self,
-        visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-        visit_under_binder: impl FnOnce(&'a Label, &'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprF<SE2, E>, Err>
-    where
-        E: Clone,
-    {
-        visitor::TraverseRefWithBindersVisitor {
-            visit_subexpr,
-            visit_under_binder,
-        }
-        .visit(self)
-    }
-
-    fn traverse_ref<'a, SE2, Err>(
-        &'a self,
-        visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprF<SE2, E>, Err>
-    where
-        E: Clone,
-    {
-        visitor::TraverseRefVisitor { visit_subexpr }.visit(self)
-    }
-
-    fn traverse_mut<'a, Err>(
-        &'a mut self,
-        visit_subexpr: impl FnMut(&'a mut SE) -> Result<(), Err>,
-    ) -> Result<(), Err> {
-        visitor::TraverseMutVisitor { visit_subexpr }.visit(self)
-    }
-
-    pub fn map_ref_with_special_handling_of_binders<'a, SE2>(
-        &'a self,
-        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
-        mut map_under_binder: impl FnMut(&'a Label, &'a SE) -> SE2,
-    ) -> ExprF<SE2, E>
-    where
-        E: Clone,
-    {
-        trivial_result(self.traverse_ref_with_special_handling_of_binders(
-            |x| Ok(map_subexpr(x)),
-            |l, x| Ok(map_under_binder(l, x)),
-        ))
-    }
-
-    pub fn map_ref<'a, SE2>(
-        &'a self,
-        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
-    ) -> ExprF<SE2, E>
-    where
-        E: Clone,
-    {
-        trivial_result(self.traverse_ref(|x| Ok(map_subexpr(x))))
-    }
-
-    pub fn map_mut<'a>(&'a mut self, mut map_subexpr: impl FnMut(&'a mut SE)) {
-        trivial_result(self.traverse_mut(|x| Ok(map_subexpr(x))))
-    }
-}
-
-impl<E> Expr<E> {
-    pub fn as_ref(&self) -> &RawExpr<E> {
-        &self.0.as_ref().0
-    }
-    pub fn as_mut(&mut self) -> &mut RawExpr<E> {
-        &mut self.0.as_mut().0
-    }
-    pub fn span(&self) -> Span {
-        self.0.as_ref().1.clone()
-    }
-
-    pub fn new(x: RawExpr<E>, n: Span) -> Self {
-        Expr(Box::new((x, n)))
-    }
-
-    pub fn rewrap<E2>(&self, x: RawExpr<E2>) -> Expr<E2> {
-        Expr(Box::new((x, (self.0).1.clone())))
-    }
-
-    pub fn traverse_resolve_mut<Err, F1>(
-        &mut self,
-        f: &mut F1,
-    ) -> Result<(), Err>
-    where
-        E: Clone,
-        F1: FnMut(Import<Expr<E>>) -> Result<E, Err>,
-    {
-        match self.as_mut() {
-            ExprF::BinOp(BinOp::ImportAlt, l, r) => {
-                let garbage_expr = ExprF::BoolLit(false);
-                let new_self = if l.traverse_resolve_mut(f).is_ok() {
-                    l
-                } else {
-                    r.traverse_resolve_mut(f)?;
-                    r
-                };
-                *self.as_mut() =
-                    std::mem::replace(new_self.as_mut(), garbage_expr);
-            }
-            _ => {
-                self.as_mut().traverse_mut(|e| e.traverse_resolve_mut(f))?;
-                if let ExprF::Import(import) = self.as_mut() {
-                    let garbage_import = Import {
-                        mode: ImportMode::Code,
-                        location: ImportLocation::Missing,
-                        hash: None,
-                    };
-                    // Move out of &mut import
-                    let import = std::mem::replace(import, garbage_import);
-                    *self.as_mut() = ExprF::Embed(f(import)?);
-                }
-            }
-        }
-        Ok(())
-    }
-}
-
-/// Add an isize to an usize
-/// Returns `None` on over/underflow
-fn add_ui(u: usize, i: isize) -> Option<usize> {
-    Some(if i < 0 {
-        u.checked_sub(i.checked_neg()? as usize)?
-    } else {
-        u.checked_add(i as usize)?
-    })
-}
-
-impl<Label: PartialEq + Clone> V<Label> {
-    pub fn shift(&self, delta: isize, var: &V<Label>) -> Option<Self> {
-        let V(x, n) = var;
-        let V(y, m) = self;
-        Some(if x == y && n <= m {
-            V(y.clone(), add_ui(*m, delta)?)
-        } else {
-            V(y.clone(), *m)
-        })
-    }
-
-    pub fn over_binder(&self, x: &Label) -> Option<Self> {
-        self.shift(-1, &V(x.clone(), 0))
-    }
-}
diff --git a/dhall/src/syntax/core/import.rs b/dhall/src/syntax/core/import.rs
deleted file mode 100644
index da3e99b..0000000
--- a/dhall/src/syntax/core/import.rs
+++ /dev/null
@@ -1,130 +0,0 @@
-/// The beginning of a file path which anchors subsequent path components
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-pub enum FilePrefix {
-    /// Absolute path
-    Absolute,
-    /// Path relative to .
-    Here,
-    /// Path relative to ..
-    Parent,
-    /// Path relative to ~
-    Home,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct FilePath {
-    pub file_path: Vec<String>,
-}
-
-/// The location of import (i.e. local vs. remote vs. environment)
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum ImportLocation<SubExpr> {
-    Local(FilePrefix, FilePath),
-    Remote(URL<SubExpr>),
-    Env(String),
-    Missing,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct URL<SubExpr> {
-    pub scheme: Scheme,
-    pub authority: String,
-    pub path: FilePath,
-    pub query: Option<String>,
-    pub headers: Option<SubExpr>,
-}
-
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-pub enum Scheme {
-    HTTP,
-    HTTPS,
-}
-
-/// How to interpret the import's contents (i.e. as Dhall code or raw text)
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-pub enum ImportMode {
-    Code,
-    RawText,
-    Location,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum Hash {
-    SHA256(Vec<u8>),
-}
-
-/// Reference to an external resource
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct Import<SubExpr> {
-    pub mode: ImportMode,
-    pub location: ImportLocation<SubExpr>,
-    pub hash: Option<Hash>,
-}
-
-impl<SE> URL<SE> {
-    pub fn traverse_ref<'a, Err, SE2>(
-        &'a self,
-        f: impl FnOnce(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<URL<SE2>, Err> {
-        let headers = self.headers.as_ref().map(f).transpose()?;
-        Ok(URL {
-            scheme: self.scheme,
-            authority: self.authority.clone(),
-            path: self.path.clone(),
-            query: self.query.clone(),
-            headers,
-        })
-    }
-    pub fn traverse_mut<'a, Err>(
-        &'a mut self,
-        f: impl FnOnce(&'a mut SE) -> Result<(), Err>,
-    ) -> Result<(), Err> {
-        if let Some(header) = &mut self.headers {
-            f(header)?;
-        }
-        Ok(())
-    }
-}
-
-impl<SE> ImportLocation<SE> {
-    pub fn traverse_ref<'a, Err, SE2>(
-        &'a self,
-        f: impl FnOnce(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<ImportLocation<SE2>, Err> {
-        use ImportLocation::*;
-        Ok(match self {
-            Local(prefix, path) => Local(*prefix, path.clone()),
-            Remote(url) => Remote(url.traverse_ref(f)?),
-            Env(env) => Env(env.clone()),
-            Missing => Missing,
-        })
-    }
-    pub fn traverse_mut<'a, Err>(
-        &'a mut self,
-        f: impl FnOnce(&'a mut SE) -> Result<(), Err>,
-    ) -> Result<(), Err> {
-        if let ImportLocation::Remote(url) = self {
-            url.traverse_mut(f)?;
-        }
-        Ok(())
-    }
-}
-
-impl<SE> Import<SE> {
-    pub fn traverse_ref<'a, Err, SE2>(
-        &'a self,
-        f: impl FnOnce(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<Import<SE2>, Err> {
-        Ok(Import {
-            mode: self.mode,
-            location: self.location.traverse_ref(f)?,
-            hash: self.hash.clone(),
-        })
-    }
-    pub fn traverse_mut<'a, Err>(
-        &'a mut self,
-        f: impl FnOnce(&'a mut SE) -> Result<(), Err>,
-    ) -> Result<(), Err> {
-        self.location.traverse_mut(f)
-    }
-}
diff --git a/dhall/src/syntax/core/label.rs b/dhall/src/syntax/core/label.rs
deleted file mode 100644
index 43c3f53..0000000
--- a/dhall/src/syntax/core/label.rs
+++ /dev/null
@@ -1,34 +0,0 @@
-use std::rc::Rc;
-
-// The type for labels throughout the AST
-// It owns the data because otherwise lifetimes would make recursive imports impossible
-#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct Label(Rc<str>);
-
-impl From<String> for Label {
-    fn from(s: String) -> Self {
-        let s: &str = &s;
-        Label(s.into())
-    }
-}
-
-impl<'a> From<&'a str> for Label {
-    fn from(s: &'a str) -> Self {
-        Label(Rc::from(s))
-    }
-}
-
-impl From<&Label> for String {
-    fn from(x: &Label) -> String {
-        x.0.as_ref().to_owned()
-    }
-}
-
-impl Label {
-    pub fn from_str(s: &str) -> Label {
-        Label(s.into())
-    }
-    pub fn as_ref(&self) -> &str {
-        self.0.as_ref()
-    }
-}
diff --git a/dhall/src/syntax/core/map.rs b/dhall/src/syntax/core/map.rs
deleted file mode 100644
index c4c6126..0000000
--- a/dhall/src/syntax/core/map.rs
+++ /dev/null
@@ -1,394 +0,0 @@
-/// A sorted map that allows multiple values for each key.
-pub use dup_tree_map::DupTreeMap;
-pub use dup_tree_set::DupTreeSet;
-
-mod one_or_more {
-    use either::Either;
-    use std::{iter, slice, vec};
-
-    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-    pub enum OneOrMore<T> {
-        One(T),
-        More(Vec<T>),
-    }
-
-    pub type Iter<'a, T> = Either<slice::Iter<'a, T>, iter::Once<&'a T>>;
-    pub type IterMut<'a, T> =
-        Either<slice::IterMut<'a, T>, iter::Once<&'a mut T>>;
-    pub type IntoIter<T> = Either<vec::IntoIter<T>, iter::Once<T>>;
-
-    impl<T> OneOrMore<T> {
-        pub fn new(x: T) -> Self {
-            OneOrMore::One(x)
-        }
-
-        pub fn push(&mut self, x: T) {
-            take_mut::take(self, |sef| match sef {
-                OneOrMore::More(mut vec) => {
-                    vec.push(x);
-                    OneOrMore::More(vec)
-                }
-                OneOrMore::One(one) => OneOrMore::More(vec![one, x]),
-            })
-        }
-
-        pub fn iter(&self) -> Iter<'_, T> {
-            match self {
-                OneOrMore::More(vec) => Either::Left(vec.iter()),
-                OneOrMore::One(x) => Either::Right(iter::once(x)),
-            }
-        }
-
-        pub fn iter_mut(&mut self) -> IterMut<'_, T> {
-            match self {
-                OneOrMore::More(vec) => Either::Left(vec.iter_mut()),
-                OneOrMore::One(x) => Either::Right(iter::once(x)),
-            }
-        }
-    }
-
-    impl<T> IntoIterator for OneOrMore<T> {
-        type Item = T;
-        type IntoIter = IntoIter<T>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            match self {
-                OneOrMore::More(vec) => Either::Left(vec.into_iter()),
-                OneOrMore::One(x) => Either::Right(iter::once(x)),
-            }
-        }
-    }
-}
-
-mod dup_tree_map {
-    use super::one_or_more;
-    use super::one_or_more::OneOrMore;
-    use std::collections::{btree_map, BTreeMap};
-    use std::iter;
-
-    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-    pub struct DupTreeMap<K, V> {
-        map: BTreeMap<K, OneOrMore<V>>,
-        size: usize,
-    }
-
-    pub type IterInternalIntermediate<'a, K, V> =
-        iter::Zip<iter::Repeat<&'a K>, one_or_more::Iter<'a, V>>;
-    pub type IterInternal<'a, K, V> = iter::FlatMap<
-        btree_map::Iter<'a, K, OneOrMore<V>>,
-        IterInternalIntermediate<'a, K, V>,
-        for<'b> fn(
-            (&'b K, &'b OneOrMore<V>),
-        ) -> IterInternalIntermediate<'b, K, V>,
-    >;
-    pub struct Iter<'a, K, V> {
-        iter: IterInternal<'a, K, V>,
-        size: usize,
-    }
-    pub type IterMutInternalIntermediate<'a, K, V> =
-        iter::Zip<iter::Repeat<&'a K>, one_or_more::IterMut<'a, V>>;
-    pub type IterMutInternal<'a, K, V> = iter::FlatMap<
-        btree_map::IterMut<'a, K, OneOrMore<V>>,
-        IterMutInternalIntermediate<'a, K, V>,
-        for<'b> fn(
-            (&'b K, &'b mut OneOrMore<V>),
-        ) -> IterMutInternalIntermediate<'b, K, V>,
-    >;
-    pub struct IterMut<'a, K, V> {
-        iter: IterMutInternal<'a, K, V>,
-        size: usize,
-    }
-    pub type IntoIterInternalIntermediate<K, V> =
-        iter::Zip<iter::Repeat<K>, one_or_more::IntoIter<V>>;
-    pub type IntoIterInternal<K, V> = iter::FlatMap<
-        btree_map::IntoIter<K, OneOrMore<V>>,
-        IntoIterInternalIntermediate<K, V>,
-        fn((K, OneOrMore<V>)) -> IntoIterInternalIntermediate<K, V>,
-    >;
-    pub struct IntoIter<K: Clone, V> {
-        iter: IntoIterInternal<K, V>,
-        size: usize,
-    }
-
-    impl<K, V> DupTreeMap<K, V> {
-        pub fn new() -> Self
-        where
-            K: Ord,
-        {
-            DupTreeMap {
-                map: BTreeMap::new(),
-                size: 0,
-            }
-        }
-
-        pub fn insert(&mut self, key: K, value: V)
-        where
-            K: Ord,
-        {
-            use std::collections::btree_map::Entry;
-            match self.map.entry(key) {
-                Entry::Vacant(e) => {
-                    e.insert(OneOrMore::new(value));
-                }
-                Entry::Occupied(mut e) => e.get_mut().push(value),
-            }
-            self.size += 1;
-        }
-
-        pub fn len(&self) -> usize {
-            self.size
-        }
-        pub fn is_empty(&self) -> bool {
-            self.size == 0
-        }
-
-        pub fn iter(&self) -> Iter<'_, K, V>
-        where
-            K: Ord,
-        {
-            fn foo<'a, K, V>(
-                (k, oom): (&'a K, &'a OneOrMore<V>),
-            ) -> IterInternalIntermediate<'a, K, V> {
-                iter::repeat(k).zip(oom.iter())
-            }
-            Iter {
-                iter: self.map.iter().flat_map(foo),
-                size: self.size,
-            }
-        }
-
-        pub fn iter_mut(&mut self) -> IterMut<'_, K, V>
-        where
-            K: Ord,
-        {
-            fn foo<'a, K, V>(
-                (k, oom): (&'a K, &'a mut OneOrMore<V>),
-            ) -> IterMutInternalIntermediate<'a, K, V> {
-                iter::repeat(k).zip(oom.iter_mut())
-            }
-            IterMut {
-                iter: self.map.iter_mut().flat_map(foo),
-                size: self.size,
-            }
-        }
-    }
-
-    impl<K, V> Default for DupTreeMap<K, V>
-    where
-        K: Ord,
-    {
-        fn default() -> Self {
-            Self::new()
-        }
-    }
-
-    impl<K, V> IntoIterator for DupTreeMap<K, V>
-    where
-        K: Ord + Clone,
-    {
-        type Item = (K, V);
-        type IntoIter = IntoIter<K, V>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            fn foo<K, V>(
-                (k, oom): (K, OneOrMore<V>),
-            ) -> IntoIterInternalIntermediate<K, V>
-            where
-                K: Clone,
-            {
-                iter::repeat(k).zip(oom.into_iter())
-            }
-            IntoIter {
-                iter: self.map.into_iter().flat_map(foo),
-                size: self.size,
-            }
-        }
-    }
-
-    impl<'a, K, V> IntoIterator for &'a DupTreeMap<K, V>
-    where
-        K: Ord,
-    {
-        type Item = (&'a K, &'a V);
-        type IntoIter = Iter<'a, K, V>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            self.iter()
-        }
-    }
-
-    impl<'a, K, V> IntoIterator for &'a mut DupTreeMap<K, V>
-    where
-        K: Ord,
-    {
-        type Item = (&'a K, &'a mut V);
-        type IntoIter = IterMut<'a, K, V>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            self.iter_mut()
-        }
-    }
-
-    impl<K, V> iter::FromIterator<(K, V)> for DupTreeMap<K, V>
-    where
-        K: Ord,
-    {
-        fn from_iter<T>(iter: T) -> Self
-        where
-            T: IntoIterator<Item = (K, V)>,
-        {
-            let mut map = DupTreeMap::new();
-            for (k, v) in iter {
-                map.insert(k, v);
-            }
-            map
-        }
-    }
-
-    impl<'a, K, V> Iterator for Iter<'a, K, V> {
-        type Item = (&'a K, &'a V);
-
-        fn next(&mut self) -> Option<Self::Item> {
-            let next = self.iter.next();
-            if next.is_some() {
-                self.size -= 1;
-            }
-            next
-        }
-
-        fn size_hint(&self) -> (usize, Option<usize>) {
-            (self.size, Some(self.size))
-        }
-    }
-
-    impl<'a, K, V> Iterator for IterMut<'a, K, V> {
-        type Item = (&'a K, &'a mut V);
-
-        fn next(&mut self) -> Option<Self::Item> {
-            let next = self.iter.next();
-            if next.is_some() {
-                self.size -= 1;
-            }
-            next
-        }
-
-        fn size_hint(&self) -> (usize, Option<usize>) {
-            (self.size, Some(self.size))
-        }
-    }
-
-    impl<K, V> Iterator for IntoIter<K, V>
-    where
-        K: Clone,
-    {
-        type Item = (K, V);
-
-        fn next(&mut self) -> Option<Self::Item> {
-            let next = self.iter.next();
-            if next.is_some() {
-                self.size -= 1;
-            }
-            next
-        }
-
-        fn size_hint(&self) -> (usize, Option<usize>) {
-            (self.size, Some(self.size))
-        }
-    }
-
-    // unsafe impl<K, V> iter::TrustedLen for IntoIter<K, V> {}
-}
-
-mod dup_tree_set {
-    use super::DupTreeMap;
-    use std::iter;
-
-    #[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-    pub struct DupTreeSet<K> {
-        map: DupTreeMap<K, ()>,
-    }
-
-    pub type Iter<'a, K> = iter::Map<
-        super::dup_tree_map::Iter<'a, K, ()>,
-        for<'b> fn((&'b K, &'b ())) -> &'b K,
-    >;
-    pub type IntoIter<K> =
-        iter::Map<super::dup_tree_map::IntoIter<K, ()>, fn((K, ())) -> K>;
-
-    impl<K> DupTreeSet<K> {
-        pub fn new() -> Self
-        where
-            K: Ord,
-        {
-            DupTreeSet {
-                map: DupTreeMap::new(),
-            }
-        }
-
-        pub fn len(&self) -> usize {
-            self.map.len()
-        }
-        pub fn is_empty(&self) -> bool {
-            self.map.is_empty()
-        }
-
-        pub fn iter(&self) -> Iter<'_, K>
-        where
-            K: Ord,
-        {
-            fn foo<'a, K>((k, ()): (&'a K, &'a ())) -> &'a K {
-                k
-            }
-            self.map.iter().map(foo)
-        }
-    }
-
-    impl<K> Default for DupTreeSet<K>
-    where
-        K: Ord,
-    {
-        fn default() -> Self {
-            Self::new()
-        }
-    }
-
-    impl<K> IntoIterator for DupTreeSet<K>
-    where
-        K: Ord + Clone,
-    {
-        type Item = K;
-        type IntoIter = IntoIter<K>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            fn foo<K>((k, ()): (K, ())) -> K {
-                k
-            }
-            self.map.into_iter().map(foo)
-        }
-    }
-
-    impl<'a, K> IntoIterator for &'a DupTreeSet<K>
-    where
-        K: Ord,
-    {
-        type Item = &'a K;
-        type IntoIter = Iter<'a, K>;
-
-        fn into_iter(self) -> Self::IntoIter {
-            self.iter()
-        }
-    }
-
-    impl<K> iter::FromIterator<K> for DupTreeSet<K>
-    where
-        K: Ord,
-    {
-        fn from_iter<T>(iter: T) -> Self
-        where
-            T: IntoIterator<Item = K>,
-        {
-            let map = iter.into_iter().map(|k| (k, ())).collect();
-            DupTreeSet { map }
-        }
-    }
-}
diff --git a/dhall/src/syntax/core/mod.rs b/dhall/src/syntax/core/mod.rs
deleted file mode 100644
index 1950154..0000000
--- a/dhall/src/syntax/core/mod.rs
+++ /dev/null
@@ -1,12 +0,0 @@
-mod expr;
-pub use expr::*;
-mod import;
-pub use import::*;
-mod label;
-pub use label::*;
-mod span;
-pub use span::*;
-mod text;
-pub use text::*;
-pub mod map;
-pub mod visitor;
diff --git a/dhall/src/syntax/core/span.rs b/dhall/src/syntax/core/span.rs
deleted file mode 100644
index f9c7008..0000000
--- a/dhall/src/syntax/core/span.rs
+++ /dev/null
@@ -1,81 +0,0 @@
-use std::rc::Rc;
-
-/// A location in the source text
-#[derive(Debug, Clone)]
-pub struct ParsedSpan {
-    input: Rc<str>,
-    /// # Safety
-    ///
-    /// Must be a valid character boundary index into `input`.
-    start: usize,
-    /// # Safety
-    ///
-    /// Must be a valid character boundary index into `input`.
-    end: usize,
-}
-
-#[derive(Debug, Clone)]
-pub enum Span {
-    /// A location in the source text
-    Parsed(ParsedSpan),
-    /// For expressions obtained from decoding binary
-    Decoded,
-    /// For expressions constructed during normalization/typecheck
-    Artificial,
-}
-
-impl Span {
-    pub(crate) fn make(input: Rc<str>, sp: pest::Span) -> Self {
-        Span::Parsed(ParsedSpan {
-            input,
-            start: sp.start(),
-            end: sp.end(),
-        })
-    }
-
-    /// Takes the union of the two spans, i.e. the range of input covered by the two spans plus any
-    /// input between them. Assumes that the spans come from the same input. Fails if one of the
-    /// spans does not point to an input location.
-    pub fn union(&self, other: &Span) -> Self {
-        use std::cmp::{max, min};
-        use Span::*;
-        match (self, other) {
-            (Parsed(x), Parsed(y)) if Rc::ptr_eq(&x.input, &y.input) => {
-                Parsed(ParsedSpan {
-                    input: x.input.clone(),
-                    start: min(x.start, y.start),
-                    end: max(x.end, y.end),
-                })
-            }
-            _ => panic!(
-                "Tried to union incompatible spans: {:?} and {:?}",
-                self, other
-            ),
-        }
-    }
-
-    /// Merges two spans assumed to point to a similar thing. If only one of them points to an
-    /// input location, use that one.
-    pub fn merge(&self, other: &Span) -> Self {
-        use Span::*;
-        match (self, other) {
-            (Parsed(x), _) | (_, Parsed(x)) => Parsed(x.clone()),
-            (Artificial, _) | (_, Artificial) => Artificial,
-            (Decoded, Decoded) => Decoded,
-        }
-    }
-
-    pub fn error(&self, message: impl Into<String>) -> String {
-        use pest::error::{Error, ErrorVariant};
-        use pest::Span;
-        let message: String = message.into();
-        let span = match self {
-            self::Span::Parsed(span) => span,
-            _ => return format!("[unknown location] {}", message),
-        };
-        let span = Span::new(&*span.input, span.start, span.end).unwrap();
-        let err: ErrorVariant<!> = ErrorVariant::CustomError { message };
-        let err = Error::new_from_span(err, span);
-        format!("{}", err)
-    }
-}
diff --git a/dhall/src/syntax/core/text.rs b/dhall/src/syntax/core/text.rs
deleted file mode 100644
index fb390ee..0000000
--- a/dhall/src/syntax/core/text.rs
+++ /dev/null
@@ -1,181 +0,0 @@
-use std::iter::FromIterator;
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct InterpolatedText<SubExpr> {
-    head: String,
-    tail: Vec<(SubExpr, String)>,
-}
-
-impl<SubExpr> From<(String, Vec<(SubExpr, String)>)>
-    for InterpolatedText<SubExpr>
-{
-    fn from(x: (String, Vec<(SubExpr, String)>)) -> Self {
-        InterpolatedText {
-            head: x.0,
-            tail: x.1,
-        }
-    }
-}
-
-impl<SubExpr> From<String> for InterpolatedText<SubExpr> {
-    fn from(s: String) -> Self {
-        InterpolatedText {
-            head: s,
-            tail: vec![],
-        }
-    }
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum InterpolatedTextContents<SubExpr> {
-    Text(String),
-    Expr(SubExpr),
-}
-
-impl<SubExpr> InterpolatedTextContents<SubExpr> {
-    pub fn is_empty(&self) -> bool {
-        use InterpolatedTextContents::{Expr, Text};
-        match self {
-            Expr(_) => false,
-            Text(s) => s.is_empty(),
-        }
-    }
-
-    pub fn traverse_ref<'a, SubExpr2, E, F>(
-        &'a self,
-        mut f: F,
-    ) -> Result<InterpolatedTextContents<SubExpr2>, E>
-    where
-        F: FnMut(&'a SubExpr) -> Result<SubExpr2, E>,
-    {
-        use InterpolatedTextContents::{Expr, Text};
-        Ok(match self {
-            Expr(e) => Expr(f(e)?),
-            Text(s) => Text(s.clone()),
-        })
-    }
-    pub fn traverse_mut<'a, E, F>(&'a mut self, mut f: F) -> Result<(), E>
-    where
-        F: FnMut(&'a mut SubExpr) -> Result<(), E>,
-    {
-        use InterpolatedTextContents::Expr;
-        if let Expr(e) = self {
-            f(e)?;
-        }
-        Ok(())
-    }
-    pub fn map_ref<'a, SubExpr2, F>(
-        &'a self,
-        mut f: F,
-    ) -> InterpolatedTextContents<SubExpr2>
-    where
-        F: FnMut(&'a SubExpr) -> SubExpr2,
-    {
-        use InterpolatedTextContents::{Expr, Text};
-        match self {
-            Expr(e) => Expr(f(e)),
-            Text(s) => Text(s.clone()),
-        }
-    }
-    pub fn map_mut<'a, F>(&'a mut self, mut f: F)
-    where
-        F: FnMut(&'a mut SubExpr),
-    {
-        use InterpolatedTextContents::Expr;
-        if let Expr(e) = self {
-            f(e);
-        }
-    }
-}
-
-impl<SubExpr> InterpolatedText<SubExpr> {
-    pub fn len(&self) -> usize {
-        1 + 2 * self.tail.len()
-    }
-
-    pub fn head(&self) -> &str {
-        &self.head
-    }
-
-    pub fn head_mut(&mut self) -> &mut String {
-        &mut self.head
-    }
-
-    pub fn is_empty(&self) -> bool {
-        self.head.is_empty() && self.tail.is_empty()
-    }
-
-    pub fn traverse_ref<'a, SubExpr2, E, F>(
-        &'a self,
-        mut f: F,
-    ) -> Result<InterpolatedText<SubExpr2>, E>
-    where
-        F: FnMut(&'a SubExpr) -> Result<SubExpr2, E>,
-    {
-        Ok(InterpolatedText {
-            head: self.head.clone(),
-            tail: self
-                .tail
-                .iter()
-                .map(|(e, s)| Ok((f(e)?, s.clone())))
-                .collect::<Result<_, _>>()?,
-        })
-    }
-
-    pub fn traverse_mut<'a, E, F>(&'a mut self, mut f: F) -> Result<(), E>
-    where
-        F: FnMut(&'a mut SubExpr) -> Result<(), E>,
-    {
-        for (e, _) in &mut self.tail {
-            f(e)?
-        }
-        Ok(())
-    }
-
-    pub fn iter<'a>(
-        &'a self,
-    ) -> impl Iterator<Item = InterpolatedTextContents<&'a SubExpr>> + 'a {
-        use std::iter::once;
-        use InterpolatedTextContents::{Expr, Text};
-        let exprs = self.tail.iter().map(|(e, _)| Expr(e));
-        let texts = self.tail.iter().map(|(_, s)| Text(s.clone()));
-        once(Text(self.head.clone())).chain(itertools::interleave(exprs, texts))
-    }
-
-    pub fn into_iter(
-        self,
-    ) -> impl Iterator<Item = InterpolatedTextContents<SubExpr>> {
-        use std::iter::once;
-        use InterpolatedTextContents::{Expr, Text};
-        once(Text(self.head)).chain(
-            self.tail
-                .into_iter()
-                .flat_map(|(e, s)| once(Expr(e)).chain(once(Text(s)))),
-        )
-    }
-}
-
-impl<SubExpr> FromIterator<InterpolatedTextContents<SubExpr>>
-    for InterpolatedText<SubExpr>
-{
-    fn from_iter<T>(iter: T) -> Self
-    where
-        T: IntoIterator<Item = InterpolatedTextContents<SubExpr>>,
-    {
-        let mut res = InterpolatedText {
-            head: String::new(),
-            tail: Vec::new(),
-        };
-        let mut crnt_str = &mut res.head;
-        for x in iter.into_iter() {
-            match x {
-                InterpolatedTextContents::Text(s) => crnt_str.push_str(&s),
-                InterpolatedTextContents::Expr(e) => {
-                    res.tail.push((e, String::new()));
-                    crnt_str = &mut res.tail.last_mut().unwrap().1;
-                }
-            }
-        }
-        res
-    }
-}
diff --git a/dhall/src/syntax/core/visitor.rs b/dhall/src/syntax/core/visitor.rs
deleted file mode 100644
index b76d037..0000000
--- a/dhall/src/syntax/core/visitor.rs
+++ /dev/null
@@ -1,360 +0,0 @@
-use crate::syntax::*;
-use std::iter::FromIterator;
-
-/// A visitor trait that can be used to traverse `ExprF`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 ExprFVisitor<'a, SE1, SE2, E1, E2>: Sized {
-    type Error;
-
-    fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>;
-    fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error>;
-
-    fn visit_subexpr_under_binder(
-        mut self,
-        _label: &'a Label,
-        subexpr: &'a SE1,
-    ) -> Result<SE2, Self::Error> {
-        self.visit_subexpr(subexpr)
-    }
-
-    fn visit(
-        self,
-        input: &'a ExprF<SE1, E1>,
-    ) -> Result<ExprF<SE2, E2>, Self::Error> {
-        visit_ref(self, input)
-    }
-}
-
-/// Like `ExprFVisitor`, but by mutable reference
-pub trait ExprFMutVisitor<'a, SE, E>: Sized {
-    type Error;
-
-    fn visit_subexpr(&mut self, subexpr: &'a mut SE)
-        -> Result<(), Self::Error>;
-    fn visit_embed(self, _embed: &'a mut E) -> Result<(), Self::Error> {
-        Ok(())
-    }
-
-    fn visit_subexpr_under_binder(
-        mut self,
-        _label: &'a mut Label,
-        subexpr: &'a mut SE,
-    ) -> Result<(), Self::Error> {
-        self.visit_subexpr(subexpr)
-    }
-
-    fn visit(self, input: &'a mut ExprF<SE, E>) -> Result<(), Self::Error> {
-        visit_mut(self, input)
-    }
-}
-
-fn visit_ref<'a, V, SE1, SE2, E1, E2>(
-    mut v: V,
-    input: &'a ExprF<SE1, E1>,
-) -> Result<ExprF<SE2, E2>, V::Error>
-where
-    V: ExprFVisitor<'a, SE1, SE2, E1, E2>,
-{
-    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, E1, E2, T>(
-        x: impl IntoIterator<Item = (&'a Label, &'a SE1)>,
-        mut v: V,
-    ) -> Result<T, V::Error>
-    where
-        SE1: 'a,
-        T: FromIterator<(Label, SE2)>,
-        V: ExprFVisitor<'a, SE1, SE2, E1, E2>,
-    {
-        x.into_iter()
-            .map(|(k, x)| Ok((k.clone(), v.visit_subexpr(x)?)))
-            .collect()
-    }
-    fn optdupmap<'a, V, SE1, SE2, E1, E2, 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: ExprFVisitor<'a, SE1, SE2, E1, E2>,
-    {
-        x.into_iter()
-            .map(|(k, x)| {
-                Ok((
-                    k.clone(),
-                    match x {
-                        Some(x) => Some(v.visit_subexpr(x)?),
-                        None => None,
-                    },
-                ))
-            })
-            .collect()
-    }
-
-    use crate::syntax::ExprF::*;
-    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)?;
-            Lam(l.clone(), t, e)
-        }
-        Pi(l, t, e) => {
-            let t = v.visit_subexpr(t)?;
-            let e = v.visit_subexpr_under_binder(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(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)?),
-        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)?)
-        }
-        Assert(e) => Assert(v.visit_subexpr(e)?),
-        Import(i) => Import(i.traverse_ref(|e| v.visit_subexpr(e))?),
-        Embed(a) => Embed(v.visit_embed(a)?),
-    })
-}
-
-fn visit_mut<'a, V, SE, E>(
-    mut v: V,
-    input: &'a mut ExprF<SE, E>,
-) -> Result<(), V::Error>
-where
-    V: ExprFMutVisitor<'a, SE, E>,
-{
-    fn vec<'a, V, SE, E>(v: &mut V, x: &'a mut Vec<SE>) -> Result<(), V::Error>
-    where
-        V: ExprFMutVisitor<'a, SE, E>,
-    {
-        for x in x {
-            v.visit_subexpr(x)?;
-        }
-        Ok(())
-    }
-    fn opt<'a, V, SE, E>(
-        v: &mut V,
-        x: &'a mut Option<SE>,
-    ) -> Result<(), V::Error>
-    where
-        V: ExprFMutVisitor<'a, SE, E>,
-    {
-        if let Some(x) = x {
-            v.visit_subexpr(x)?;
-        }
-        Ok(())
-    }
-    fn dupmap<'a, V, SE, E>(
-        mut v: V,
-        x: impl IntoIterator<Item = (&'a Label, &'a mut SE)>,
-    ) -> Result<(), V::Error>
-    where
-        SE: 'a,
-        V: ExprFMutVisitor<'a, SE, E>,
-    {
-        for (_, x) in x {
-            v.visit_subexpr(x)?;
-        }
-        Ok(())
-    }
-    fn optdupmap<'a, V, SE, E>(
-        mut v: V,
-        x: impl IntoIterator<Item = (&'a Label, &'a mut Option<SE>)>,
-    ) -> Result<(), V::Error>
-    where
-        SE: 'a,
-        V: ExprFMutVisitor<'a, SE, E>,
-    {
-        for (_, x) in x {
-            opt(&mut v, x)?;
-        }
-        Ok(())
-    }
-
-    use crate::syntax::ExprF::*;
-    match input {
-        Var(_) | Const(_) | Builtin(_) | BoolLit(_) | NaturalLit(_)
-        | IntegerLit(_) | DoubleLit(_) => {}
-        Lam(l, t, e) => {
-            v.visit_subexpr(t)?;
-            v.visit_subexpr_under_binder(l, e)?;
-        }
-        Pi(l, t, e) => {
-            v.visit_subexpr(t)?;
-            v.visit_subexpr_under_binder(l, e)?;
-        }
-        Let(l, t, a, e) => {
-            opt(&mut v, t)?;
-            v.visit_subexpr(a)?;
-            v.visit_subexpr_under_binder(l, e)?;
-        }
-        App(f, a) => {
-            v.visit_subexpr(f)?;
-            v.visit_subexpr(a)?;
-        }
-        Annot(x, t) => {
-            v.visit_subexpr(x)?;
-            v.visit_subexpr(t)?;
-        }
-        TextLit(t) => t.traverse_mut(|e| v.visit_subexpr(e))?,
-        BinOp(_, x, y) => {
-            v.visit_subexpr(x)?;
-            v.visit_subexpr(y)?;
-        }
-        BoolIf(b, t, f) => {
-            v.visit_subexpr(b)?;
-            v.visit_subexpr(t)?;
-            v.visit_subexpr(f)?;
-        }
-        EmptyListLit(t) => v.visit_subexpr(t)?,
-        NEListLit(es) => vec(&mut v, es)?,
-        SomeLit(e) => v.visit_subexpr(e)?,
-        RecordType(kts) => dupmap(v, kts)?,
-        RecordLit(kvs) => dupmap(v, kvs)?,
-        UnionType(kts) => optdupmap(v, kts)?,
-        Merge(x, y, t) => {
-            v.visit_subexpr(x)?;
-            v.visit_subexpr(y)?;
-            opt(&mut v, t)?;
-        }
-        ToMap(x, t) => {
-            v.visit_subexpr(x)?;
-            opt(&mut v, t)?;
-        }
-        Field(e, _) => v.visit_subexpr(e)?,
-        Projection(e, _) => v.visit_subexpr(e)?,
-        ProjectionByExpr(e, x) => {
-            v.visit_subexpr(e)?;
-            v.visit_subexpr(x)?;
-        }
-        Assert(e) => v.visit_subexpr(e)?,
-        Import(i) => i.traverse_mut(|e| v.visit_subexpr(e))?,
-        Embed(a) => v.visit_embed(a)?,
-    }
-    Ok(())
-}
-
-pub struct TraverseRefWithBindersVisitor<F1, F2> {
-    pub visit_subexpr: F1,
-    pub visit_under_binder: F2,
-}
-
-impl<'a, SE, E, SE2, Err, F1, F2> ExprFVisitor<'a, SE, SE2, E, E>
-    for TraverseRefWithBindersVisitor<F1, F2>
-where
-    SE: 'a,
-    E: 'a + Clone,
-    F1: FnMut(&'a SE) -> Result<SE2, Err>,
-    F2: FnOnce(&'a Label, &'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_subexpr_under_binder(
-        self,
-        label: &'a Label,
-        subexpr: &'a SE,
-    ) -> Result<SE2, Self::Error> {
-        (self.visit_under_binder)(label, subexpr)
-    }
-    fn visit_embed(self, embed: &'a E) -> Result<E, Self::Error> {
-        Ok(embed.clone())
-    }
-}
-
-pub struct TraverseRefVisitor<F1> {
-    pub visit_subexpr: F1,
-}
-
-impl<'a, SE, E, SE2, Err, F1> ExprFVisitor<'a, SE, SE2, E, E>
-    for TraverseRefVisitor<F1>
-where
-    SE: 'a,
-    E: 'a + Clone,
-    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_embed(self, embed: &'a E) -> Result<E, Self::Error> {
-        Ok(embed.clone())
-    }
-}
-
-pub struct TraverseMutVisitor<F1> {
-    pub visit_subexpr: F1,
-}
-
-impl<'a, SE, E, Err, F1> ExprFMutVisitor<'a, SE, E> for TraverseMutVisitor<F1>
-where
-    SE: 'a,
-    E: 'a,
-    F1: FnMut(&'a mut SE) -> Result<(), Err>,
-{
-    type Error = Err;
-
-    fn visit_subexpr(
-        &mut self,
-        subexpr: &'a mut SE,
-    ) -> Result<(), Self::Error> {
-        (self.visit_subexpr)(subexpr)
-    }
-}