From 881248d2c4f0b4556a23d671d355bb7258adf8bb Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 17 Dec 2019 14:33:06 +0000
Subject: Rename syntax::core to syntax::ast

---
 dhall/src/syntax/ast/expr.rs    | 377 ++++++++++++++++++++++++++++++++++++++
 dhall/src/syntax/ast/import.rs  | 130 +++++++++++++
 dhall/src/syntax/ast/label.rs   |  34 ++++
 dhall/src/syntax/ast/map.rs     | 394 ++++++++++++++++++++++++++++++++++++++++
 dhall/src/syntax/ast/mod.rs     |  12 ++
 dhall/src/syntax/ast/span.rs    |  81 +++++++++
 dhall/src/syntax/ast/text.rs    | 181 ++++++++++++++++++
 dhall/src/syntax/ast/visitor.rs | 360 ++++++++++++++++++++++++++++++++++++
 8 files changed, 1569 insertions(+)
 create mode 100644 dhall/src/syntax/ast/expr.rs
 create mode 100644 dhall/src/syntax/ast/import.rs
 create mode 100644 dhall/src/syntax/ast/label.rs
 create mode 100644 dhall/src/syntax/ast/map.rs
 create mode 100644 dhall/src/syntax/ast/mod.rs
 create mode 100644 dhall/src/syntax/ast/span.rs
 create mode 100644 dhall/src/syntax/ast/text.rs
 create mode 100644 dhall/src/syntax/ast/visitor.rs

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
new file mode 100644
index 0000000..5b9f401
--- /dev/null
+++ b/dhall/src/syntax/ast/expr.rs
@@ -0,0 +1,377 @@
+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/ast/import.rs b/dhall/src/syntax/ast/import.rs
new file mode 100644
index 0000000..da3e99b
--- /dev/null
+++ b/dhall/src/syntax/ast/import.rs
@@ -0,0 +1,130 @@
+/// 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/ast/label.rs b/dhall/src/syntax/ast/label.rs
new file mode 100644
index 0000000..43c3f53
--- /dev/null
+++ b/dhall/src/syntax/ast/label.rs
@@ -0,0 +1,34 @@
+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/ast/map.rs b/dhall/src/syntax/ast/map.rs
new file mode 100644
index 0000000..c4c6126
--- /dev/null
+++ b/dhall/src/syntax/ast/map.rs
@@ -0,0 +1,394 @@
+/// 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/ast/mod.rs b/dhall/src/syntax/ast/mod.rs
new file mode 100644
index 0000000..1950154
--- /dev/null
+++ b/dhall/src/syntax/ast/mod.rs
@@ -0,0 +1,12 @@
+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/ast/span.rs b/dhall/src/syntax/ast/span.rs
new file mode 100644
index 0000000..f9c7008
--- /dev/null
+++ b/dhall/src/syntax/ast/span.rs
@@ -0,0 +1,81 @@
+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/ast/text.rs b/dhall/src/syntax/ast/text.rs
new file mode 100644
index 0000000..fb390ee
--- /dev/null
+++ b/dhall/src/syntax/ast/text.rs
@@ -0,0 +1,181 @@
+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/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
new file mode 100644
index 0000000..b76d037
--- /dev/null
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -0,0 +1,360 @@
+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)
+    }
+}
-- 
cgit v1.2.3


From e355984c3c83f8288eac36023c361db869643367 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 18:12:10 +0000
Subject: s/ExprF/ExprKind/

---
 dhall/src/syntax/ast/expr.rs    | 24 ++++++++++-----------
 dhall/src/syntax/ast/visitor.rs | 47 +++++++++++++++++++++--------------------
 2 files changed, 36 insertions(+), 35 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 5b9f401..7ac342d 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, ExprFMutVisitor, ExprFVisitor};
+use crate::syntax::visitor::{self, ExprKindMutVisitor, ExprKindVisitor};
 use crate::syntax::*;
 
 pub type Integer = isize;
@@ -144,7 +144,7 @@ pub enum Builtin {
 #[derive(Debug, Clone)]
 pub struct Expr<Embed>(Box<(RawExpr<Embed>, Span)>);
 
-pub type RawExpr<Embed> = ExprF<Expr<Embed>, Embed>;
+pub type RawExpr<Embed> = ExprKind<Expr<Embed>, Embed>;
 
 impl<Embed: PartialEq> std::cmp::PartialEq for Expr<Embed> {
     fn eq(&self, other: &Self) -> bool {
@@ -168,7 +168,7 @@ impl<Embed: std::hash::Hash> std::hash::Hash for Expr<Embed> {
 // much more generic code and improves pattern-matching behind
 // smart pointers.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum ExprF<SubExpr, Embed> {
+pub enum ExprKind<SubExpr, Embed> {
     Const(Const),
     ///  `x`
     ///  `x@n`
@@ -231,12 +231,12 @@ pub enum ExprF<SubExpr, Embed> {
     Embed(Embed),
 }
 
-impl<SE, E> ExprF<SE, E> {
+impl<SE, E> ExprKind<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>
+    ) -> Result<ExprKind<SE2, E>, Err>
     where
         E: Clone,
     {
@@ -250,7 +250,7 @@ impl<SE, E> ExprF<SE, E> {
     fn traverse_ref<'a, SE2, Err>(
         &'a self,
         visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprF<SE2, E>, Err>
+    ) -> Result<ExprKind<SE2, E>, Err>
     where
         E: Clone,
     {
@@ -268,7 +268,7 @@ impl<SE, E> ExprF<SE, E> {
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
         mut map_under_binder: impl FnMut(&'a Label, &'a SE) -> SE2,
-    ) -> ExprF<SE2, E>
+    ) -> ExprKind<SE2, E>
     where
         E: Clone,
     {
@@ -281,7 +281,7 @@ impl<SE, E> ExprF<SE, E> {
     pub fn map_ref<'a, SE2>(
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
-    ) -> ExprF<SE2, E>
+    ) -> ExprKind<SE2, E>
     where
         E: Clone,
     {
@@ -321,8 +321,8 @@ impl<E> Expr<E> {
         F1: FnMut(Import<Expr<E>>) -> Result<E, Err>,
     {
         match self.as_mut() {
-            ExprF::BinOp(BinOp::ImportAlt, l, r) => {
-                let garbage_expr = ExprF::BoolLit(false);
+            ExprKind::BinOp(BinOp::ImportAlt, l, r) => {
+                let garbage_expr = ExprKind::BoolLit(false);
                 let new_self = if l.traverse_resolve_mut(f).is_ok() {
                     l
                 } else {
@@ -334,7 +334,7 @@ impl<E> Expr<E> {
             }
             _ => {
                 self.as_mut().traverse_mut(|e| e.traverse_resolve_mut(f))?;
-                if let ExprF::Import(import) = self.as_mut() {
+                if let ExprKind::Import(import) = self.as_mut() {
                     let garbage_import = Import {
                         mode: ImportMode::Code,
                         location: ImportLocation::Missing,
@@ -342,7 +342,7 @@ impl<E> Expr<E> {
                     };
                     // Move out of &mut import
                     let import = std::mem::replace(import, garbage_import);
-                    *self.as_mut() = ExprF::Embed(f(import)?);
+                    *self.as_mut() = ExprKind::Embed(f(import)?);
                 }
             }
         }
diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
index b76d037..b557995 100644
--- a/dhall/src/syntax/ast/visitor.rs
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -1,7 +1,7 @@
 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
+/// 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
@@ -9,7 +9,7 @@ use std::iter::FromIterator;
 /// 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 {
+pub trait ExprKindVisitor<'a, SE1, SE2, E1, E2>: Sized {
     type Error;
 
     fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>;
@@ -25,14 +25,14 @@ pub trait ExprFVisitor<'a, SE1, SE2, E1, E2>: Sized {
 
     fn visit(
         self,
-        input: &'a ExprF<SE1, E1>,
-    ) -> Result<ExprF<SE2, E2>, Self::Error> {
+        input: &'a ExprKind<SE1, E1>,
+    ) -> Result<ExprKind<SE2, E2>, Self::Error> {
         visit_ref(self, input)
     }
 }
 
-/// Like `ExprFVisitor`, but by mutable reference
-pub trait ExprFMutVisitor<'a, SE, E>: Sized {
+/// Like `ExprKindVisitor`, but by mutable reference
+pub trait ExprKindMutVisitor<'a, SE, E>: Sized {
     type Error;
 
     fn visit_subexpr(&mut self, subexpr: &'a mut SE)
@@ -49,17 +49,17 @@ pub trait ExprFMutVisitor<'a, SE, E>: Sized {
         self.visit_subexpr(subexpr)
     }
 
-    fn visit(self, input: &'a mut ExprF<SE, E>) -> Result<(), Self::Error> {
+    fn visit(self, input: &'a mut ExprKind<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>
+    input: &'a ExprKind<SE1, E1>,
+) -> Result<ExprKind<SE2, E2>, V::Error>
 where
-    V: ExprFVisitor<'a, SE1, SE2, E1, E2>,
+    V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
 {
     fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>(
         x: &'a [T],
@@ -83,7 +83,7 @@ where
     where
         SE1: 'a,
         T: FromIterator<(Label, SE2)>,
-        V: ExprFVisitor<'a, SE1, SE2, E1, E2>,
+        V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
     {
         x.into_iter()
             .map(|(k, x)| Ok((k.clone(), v.visit_subexpr(x)?)))
@@ -96,7 +96,7 @@ where
     where
         SE1: 'a,
         T: FromIterator<(Label, Option<SE2>)>,
-        V: ExprFVisitor<'a, SE1, SE2, E1, E2>,
+        V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
     {
         x.into_iter()
             .map(|(k, x)| {
@@ -111,7 +111,7 @@ where
             .collect()
     }
 
-    use crate::syntax::ExprF::*;
+    use crate::syntax::ExprKind::*;
     Ok(match input {
         Var(v) => Var(v.clone()),
         Lam(l, t, e) => {
@@ -172,14 +172,14 @@ where
 
 fn visit_mut<'a, V, SE, E>(
     mut v: V,
-    input: &'a mut ExprF<SE, E>,
+    input: &'a mut ExprKind<SE, E>,
 ) -> Result<(), V::Error>
 where
-    V: ExprFMutVisitor<'a, SE, E>,
+    V: ExprKindMutVisitor<'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>,
+        V: ExprKindMutVisitor<'a, SE, E>,
     {
         for x in x {
             v.visit_subexpr(x)?;
@@ -191,7 +191,7 @@ where
         x: &'a mut Option<SE>,
     ) -> Result<(), V::Error>
     where
-        V: ExprFMutVisitor<'a, SE, E>,
+        V: ExprKindMutVisitor<'a, SE, E>,
     {
         if let Some(x) = x {
             v.visit_subexpr(x)?;
@@ -204,7 +204,7 @@ where
     ) -> Result<(), V::Error>
     where
         SE: 'a,
-        V: ExprFMutVisitor<'a, SE, E>,
+        V: ExprKindMutVisitor<'a, SE, E>,
     {
         for (_, x) in x {
             v.visit_subexpr(x)?;
@@ -217,7 +217,7 @@ where
     ) -> Result<(), V::Error>
     where
         SE: 'a,
-        V: ExprFMutVisitor<'a, SE, E>,
+        V: ExprKindMutVisitor<'a, SE, E>,
     {
         for (_, x) in x {
             opt(&mut v, x)?;
@@ -225,7 +225,7 @@ where
         Ok(())
     }
 
-    use crate::syntax::ExprF::*;
+    use crate::syntax::ExprKind::*;
     match input {
         Var(_) | Const(_) | Builtin(_) | BoolLit(_) | NaturalLit(_)
         | IntegerLit(_) | DoubleLit(_) => {}
@@ -293,7 +293,7 @@ pub struct TraverseRefWithBindersVisitor<F1, F2> {
     pub visit_under_binder: F2,
 }
 
-impl<'a, SE, E, SE2, Err, F1, F2> ExprFVisitor<'a, SE, SE2, E, E>
+impl<'a, SE, E, SE2, Err, F1, F2> ExprKindVisitor<'a, SE, SE2, E, E>
     for TraverseRefWithBindersVisitor<F1, F2>
 where
     SE: 'a,
@@ -322,7 +322,7 @@ pub struct TraverseRefVisitor<F1> {
     pub visit_subexpr: F1,
 }
 
-impl<'a, SE, E, SE2, Err, F1> ExprFVisitor<'a, SE, SE2, E, E>
+impl<'a, SE, E, SE2, Err, F1> ExprKindVisitor<'a, SE, SE2, E, E>
     for TraverseRefVisitor<F1>
 where
     SE: 'a,
@@ -343,7 +343,8 @@ pub struct TraverseMutVisitor<F1> {
     pub visit_subexpr: F1,
 }
 
-impl<'a, SE, E, Err, F1> ExprFMutVisitor<'a, SE, E> for TraverseMutVisitor<F1>
+impl<'a, SE, E, Err, F1> ExprKindMutVisitor<'a, SE, E>
+    for TraverseMutVisitor<F1>
 where
     SE: 'a,
     E: 'a,
-- 
cgit v1.2.3


From 515f6d70cf724d9927f4466ed1cd4300d20b4b09 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 18:14:18 +0000
Subject: Reorganize ast::expr

---
 dhall/src/syntax/ast/expr.rs | 151 ++++++++++++++++++++++---------------------
 1 file changed, 76 insertions(+), 75 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 7ac342d..a85b837 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -6,46 +6,10 @@ 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 {
@@ -62,18 +26,6 @@ pub enum Const {
 #[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)]
@@ -146,23 +98,6 @@ pub struct Expr<Embed>(Box<(RawExpr<Embed>, Span)>);
 
 pub type RawExpr<Embed> = ExprKind<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
@@ -350,16 +285,6 @@ impl<E> Expr<E> {
     }
 }
 
-/// 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;
@@ -375,3 +300,79 @@ impl<Label: PartialEq + Clone> V<Label> {
         self.shift(-1, &V(x.clone(), 0))
     }
 }
+
+pub fn trivial_result<T>(x: Result<T, !>) -> T {
+    match x {
+        Ok(x) => x,
+        Err(e) => e,
+    }
+}
+
+/// 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 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
+    }
+}
+
+// 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)
+    }
+}
+
+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)
+    }
+}
-- 
cgit v1.2.3


From 99a2fdf5bf92d051d154c24ce95c444bccb30609 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 18:16:51 +0000
Subject: Remove an unused impl

---
 dhall/src/syntax/ast/expr.rs | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index a85b837..9f19ddb 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -347,19 +347,13 @@ impl From<NaiveDouble> for f64 {
     }
 }
 
-// This is only for the specific `Label` type, not generic
+/// 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)
-    }
-}
-
 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
-- 
cgit v1.2.3


From dfc1511b25f66f60cccdae727e7b54946e2edcb6 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 18:23:26 +0000
Subject: Use a named struct instead of a tuple in Expr

---
 dhall/src/syntax/ast/expr.rs | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 9f19ddb..93c2311 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -94,7 +94,10 @@ pub enum Builtin {
 
 // Each node carries an annotation.
 #[derive(Debug, Clone)]
-pub struct Expr<Embed>(Box<(RawExpr<Embed>, Span)>);
+pub struct Expr<Embed> {
+    kind: Box<ExprKind<Expr<Embed>, Embed>>,
+    span: Span,
+}
 
 pub type RawExpr<Embed> = ExprKind<Expr<Embed>, Embed>;
 
@@ -230,21 +233,27 @@ impl<SE, E> ExprKind<SE, E> {
 
 impl<E> Expr<E> {
     pub fn as_ref(&self) -> &RawExpr<E> {
-        &self.0.as_ref().0
+        &self.kind
     }
     pub fn as_mut(&mut self) -> &mut RawExpr<E> {
-        &mut self.0.as_mut().0
+        &mut self.kind
     }
     pub fn span(&self) -> Span {
-        self.0.as_ref().1.clone()
+        self.span.clone()
     }
 
-    pub fn new(x: RawExpr<E>, n: Span) -> Self {
-        Expr(Box::new((x, n)))
+    pub fn new(kind: RawExpr<E>, span: Span) -> Self {
+        Expr {
+            kind: Box::new(kind),
+            span,
+        }
     }
 
-    pub fn rewrap<E2>(&self, x: RawExpr<E2>) -> Expr<E2> {
-        Expr(Box::new((x, (self.0).1.clone())))
+    pub fn rewrap<E2>(&self, kind: RawExpr<E2>) -> Expr<E2> {
+        Expr {
+            kind: Box::new(kind),
+            span: self.span.clone(),
+        }
     }
 
     pub fn traverse_resolve_mut<Err, F1>(
@@ -356,7 +365,7 @@ impl From<Label> for V<Label> {
 
 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
+        self.kind == other.kind
     }
 }
 
@@ -367,6 +376,6 @@ impl<Embed: std::hash::Hash> std::hash::Hash for Expr<Embed> {
     where
         H: std::hash::Hasher,
     {
-        (self.0).0.hash(state)
+        self.kind.hash(state)
     }
 }
-- 
cgit v1.2.3


From 980e50f33a88559edcf8b12cdec91fd9bee84ca9 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 19:01:07 +0000
Subject: s/RawExpr/UnspannedExpr/

---
 dhall/src/syntax/ast/expr.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 93c2311..410fb1d 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -99,7 +99,7 @@ pub struct Expr<Embed> {
     span: Span,
 }
 
-pub type RawExpr<Embed> = ExprKind<Expr<Embed>, Embed>;
+pub type UnspannedExpr<Embed> = ExprKind<Expr<Embed>, Embed>;
 
 /// Syntax tree for expressions
 // Having the recursion out of the enum definition enables writing
@@ -232,24 +232,24 @@ impl<SE, E> ExprKind<SE, E> {
 }
 
 impl<E> Expr<E> {
-    pub fn as_ref(&self) -> &RawExpr<E> {
+    pub fn as_ref(&self) -> &UnspannedExpr<E> {
         &self.kind
     }
-    pub fn as_mut(&mut self) -> &mut RawExpr<E> {
+    pub fn as_mut(&mut self) -> &mut UnspannedExpr<E> {
         &mut self.kind
     }
     pub fn span(&self) -> Span {
         self.span.clone()
     }
 
-    pub fn new(kind: RawExpr<E>, span: Span) -> Self {
+    pub fn new(kind: UnspannedExpr<E>, span: Span) -> Self {
         Expr {
             kind: Box::new(kind),
             span,
         }
     }
 
-    pub fn rewrap<E2>(&self, kind: RawExpr<E2>) -> Expr<E2> {
+    pub fn rewrap<E2>(&self, kind: UnspannedExpr<E2>) -> Expr<E2> {
         Expr {
             kind: Box::new(kind),
             span: self.span.clone(),
-- 
cgit v1.2.3


From 08593ae84ceae4d5f639d5868c08b99f1622795a Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Fri, 20 Dec 2019 19:07:50 +0000
Subject: Remove Expr::as_mut

---
 dhall/src/syntax/ast/expr.rs | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

(limited to 'dhall/src/syntax/ast')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 410fb1d..48c48d8 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -235,9 +235,6 @@ impl<E> Expr<E> {
     pub fn as_ref(&self) -> &UnspannedExpr<E> {
         &self.kind
     }
-    pub fn as_mut(&mut self) -> &mut UnspannedExpr<E> {
-        &mut self.kind
-    }
     pub fn span(&self) -> Span {
         self.span.clone()
     }
@@ -264,7 +261,7 @@ impl<E> Expr<E> {
         E: Clone,
         F1: FnMut(Import<Expr<E>>) -> Result<E, Err>,
     {
-        match self.as_mut() {
+        match self.kind.as_mut() {
             ExprKind::BinOp(BinOp::ImportAlt, l, r) => {
                 let garbage_expr = ExprKind::BoolLit(false);
                 let new_self = if l.traverse_resolve_mut(f).is_ok() {
@@ -273,12 +270,12 @@ impl<E> Expr<E> {
                     r.traverse_resolve_mut(f)?;
                     r
                 };
-                *self.as_mut() =
-                    std::mem::replace(new_self.as_mut(), garbage_expr);
+                *self.kind =
+                    std::mem::replace(new_self.kind.as_mut(), garbage_expr);
             }
             _ => {
-                self.as_mut().traverse_mut(|e| e.traverse_resolve_mut(f))?;
-                if let ExprKind::Import(import) = self.as_mut() {
+                self.kind.traverse_mut(|e| e.traverse_resolve_mut(f))?;
+                if let ExprKind::Import(import) = self.kind.as_mut() {
                     let garbage_import = Import {
                         mode: ImportMode::Code,
                         location: ImportLocation::Missing,
@@ -286,7 +283,7 @@ impl<E> Expr<E> {
                     };
                     // Move out of &mut import
                     let import = std::mem::replace(import, garbage_import);
-                    *self.as_mut() = ExprKind::Embed(f(import)?);
+                    *self.kind = ExprKind::Embed(f(import)?);
                 }
             }
         }
-- 
cgit v1.2.3