From 423fdeebe9247b16744fae4b50df415bbd08be04 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 6 May 2019 22:09:55 +0200
Subject: Reorganize dhall into a phase structure

---
 dhall/src/phase/binary.rs    |  363 ++++++++
 dhall/src/phase/mod.rs       |  389 +++++++++
 dhall/src/phase/normalize.rs | 1888 ++++++++++++++++++++++++++++++++++++++++++
 dhall/src/phase/parse.rs     |   38 +
 dhall/src/phase/resolve.rs   |  139 ++++
 dhall/src/phase/typecheck.rs | 1276 ++++++++++++++++++++++++++++
 6 files changed, 4093 insertions(+)
 create mode 100644 dhall/src/phase/binary.rs
 create mode 100644 dhall/src/phase/mod.rs
 create mode 100644 dhall/src/phase/normalize.rs
 create mode 100644 dhall/src/phase/parse.rs
 create mode 100644 dhall/src/phase/resolve.rs
 create mode 100644 dhall/src/phase/typecheck.rs

(limited to 'dhall/src/phase')

diff --git a/dhall/src/phase/binary.rs b/dhall/src/phase/binary.rs
new file mode 100644
index 0000000..9c31d4c
--- /dev/null
+++ b/dhall/src/phase/binary.rs
@@ -0,0 +1,363 @@
+use dhall_syntax::*;
+use itertools::*;
+use serde_cbor::value::value as cbor;
+
+type ParsedExpr = SubExpr<X, Import>;
+
+#[derive(Debug)]
+pub enum DecodeError {
+    CBORError(serde_cbor::error::Error),
+    WrongFormatError(String),
+}
+
+pub fn decode(data: &[u8]) -> Result<ParsedExpr, DecodeError> {
+    match serde_cbor::de::from_slice(data) {
+        Ok(v) => cbor_value_to_dhall(&v),
+        Err(e) => Err(DecodeError::CBORError(e)),
+    }
+}
+
+fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
+    use cbor::Value::*;
+    use dhall_syntax::{BinOp, Builtin, Const};
+    use ExprF::*;
+    Ok(rc(match data {
+        String(s) => match Builtin::parse(s) {
+            Some(b) => ExprF::Builtin(b),
+            None => match s.as_str() {
+                "True" => BoolLit(true),
+                "False" => BoolLit(false),
+                "Type" => Const(Const::Type),
+                "Kind" => Const(Const::Kind),
+                "Sort" => Const(Const::Sort),
+                _ => Err(DecodeError::WrongFormatError("builtin".to_owned()))?,
+            },
+        },
+        U64(n) => Var(V(Label::from("_"), *n as usize)),
+        F64(x) => DoubleLit((*x).into()),
+        Bool(b) => BoolLit(*b),
+        Array(vec) => match vec.as_slice() {
+            [String(l), U64(n)] => {
+                let l = Label::from(l.as_str());
+                Var(V(l, *n as usize))
+            }
+            [U64(0), f, args..] => {
+                let mut f = cbor_value_to_dhall(&f)?;
+                for a in args {
+                    let a = cbor_value_to_dhall(&a)?;
+                    f = rc(App(f, a))
+                }
+                return Ok(f);
+            }
+            [U64(1), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                Lam(Label::from("_"), x, y)
+            }
+            [U64(1), String(l), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                let l = Label::from(l.as_str());
+                Lam(l, x, y)
+            }
+            [U64(2), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                Pi(Label::from("_"), x, y)
+            }
+            [U64(2), String(l), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                let l = Label::from(l.as_str());
+                Pi(l, x, y)
+            }
+            [U64(3), U64(n), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                use BinOp::*;
+                let op = match n {
+                    0 => BoolOr,
+                    1 => BoolAnd,
+                    2 => BoolEQ,
+                    3 => BoolNE,
+                    4 => NaturalPlus,
+                    5 => NaturalTimes,
+                    6 => TextAppend,
+                    7 => ListAppend,
+                    8 => Combine,
+                    9 => Prefer,
+                    10 => CombineTypes,
+                    11 => ImportAlt,
+                    _ => {
+                        Err(DecodeError::WrongFormatError("binop".to_owned()))?
+                    }
+                };
+                BinOp(op, x, y)
+            }
+            [U64(4), t] => {
+                let t = cbor_value_to_dhall(&t)?;
+                EmptyListLit(t)
+            }
+            [U64(4), Null, rest..] => {
+                let rest = rest
+                    .iter()
+                    .map(cbor_value_to_dhall)
+                    .collect::<Result<Vec<_>, _>>()?;
+                NEListLit(rest)
+            }
+            [U64(5), t] => {
+                let t = cbor_value_to_dhall(&t)?;
+                OldOptionalLit(None, t)
+            }
+            [U64(5), Null, x] => {
+                let x = cbor_value_to_dhall(&x)?;
+                SomeLit(x)
+            }
+            [U64(5), t, x] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let t = cbor_value_to_dhall(&t)?;
+                OldOptionalLit(Some(x), t)
+            }
+            [U64(6), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                Merge(x, y, None)
+            }
+            [U64(6), x, y, z] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                let z = cbor_value_to_dhall(&z)?;
+                Merge(x, y, Some(z))
+            }
+            [U64(7), Object(map)] => {
+                let map = cbor_map_to_dhall_map(map)?;
+                RecordType(map)
+            }
+            [U64(8), Object(map)] => {
+                let map = cbor_map_to_dhall_map(map)?;
+                RecordLit(map)
+            }
+            [U64(9), x, String(l)] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let l = Label::from(l.as_str());
+                Field(x, l)
+            }
+            [U64(11), Object(map)] => {
+                let map = cbor_map_to_dhall_opt_map(map)?;
+                UnionType(map)
+            }
+            [U64(12), String(l), x, Object(map)] => {
+                let map = cbor_map_to_dhall_opt_map(map)?;
+                let x = cbor_value_to_dhall(&x)?;
+                let l = Label::from(l.as_str());
+                UnionLit(l, x, map)
+            }
+            [U64(14), x, y, z] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                let z = cbor_value_to_dhall(&z)?;
+                BoolIf(x, y, z)
+            }
+            [U64(15), U64(x)] => NaturalLit(*x as Natural),
+            [U64(16), U64(x)] => IntegerLit(*x as Integer),
+            [U64(16), I64(x)] => IntegerLit(*x as Integer),
+            [U64(18), String(first), rest..] => {
+                TextLit(InterpolatedText::from((
+                    first.clone(),
+                    rest.iter()
+                        .tuples()
+                        .map(|(x, y)| {
+                            let x = cbor_value_to_dhall(&x)?;
+                            let y = match y {
+                                String(s) => s.clone(),
+                                _ => Err(DecodeError::WrongFormatError(
+                                    "text".to_owned(),
+                                ))?,
+                            };
+                            Ok((x, y))
+                        })
+                        .collect::<Result<_, _>>()?,
+                )))
+            }
+            [U64(24), hash, U64(mode), U64(scheme), rest..] => {
+                let mode = match mode {
+                    1 => ImportMode::RawText,
+                    _ => ImportMode::Code,
+                };
+                let hash = match hash {
+                    Null => None,
+                    Array(vec) => match vec.as_slice() {
+                        [String(protocol), String(hash)] => Some(Hash {
+                            protocol: protocol.clone(),
+                            hash: hash.clone(),
+                        }),
+                        _ => Err(DecodeError::WrongFormatError(
+                            "import/hash".to_owned(),
+                        ))?,
+                    },
+                    _ => Err(DecodeError::WrongFormatError(
+                        "import/hash".to_owned(),
+                    ))?,
+                };
+                let mut rest = rest.iter();
+                let location = match scheme {
+                    0 | 1 => {
+                        let scheme = match scheme {
+                            0 => Scheme::HTTP,
+                            _ => Scheme::HTTPS,
+                        };
+                        let headers = match rest.next() {
+                            Some(Null) => None,
+                            Some(x) => {
+                                match cbor_value_to_dhall(&x)?.as_ref() {
+                                    Embed(import) => Some(Box::new(
+                                        import.location_hashed.clone(),
+                                    )),
+                                    _ => Err(DecodeError::WrongFormatError(
+                                        "import/remote/headers".to_owned(),
+                                    ))?,
+                                }
+                            }
+                            _ => Err(DecodeError::WrongFormatError(
+                                "import/remote/headers".to_owned(),
+                            ))?,
+                        };
+                        let authority = match rest.next() {
+                            Some(String(s)) => s.to_owned(),
+                            _ => Err(DecodeError::WrongFormatError(
+                                "import/remote/authority".to_owned(),
+                            ))?,
+                        };
+                        let query = match rest.next_back() {
+                            Some(Null) => None,
+                            Some(String(s)) => Some(s.to_owned()),
+                            _ => Err(DecodeError::WrongFormatError(
+                                "import/remote/query".to_owned(),
+                            ))?,
+                        };
+                        let path = rest
+                            .map(|s| {
+                                s.as_string().ok_or_else(|| {
+                                    DecodeError::WrongFormatError(
+                                        "import/remote/path".to_owned(),
+                                    )
+                                })
+                            })
+                            .collect::<Result<_, _>>()?;
+                        ImportLocation::Remote(URL {
+                            scheme,
+                            authority,
+                            path,
+                            query,
+                            headers,
+                        })
+                    }
+                    2 | 3 | 4 | 5 => {
+                        let prefix = match scheme {
+                            2 => FilePrefix::Absolute,
+                            3 => FilePrefix::Here,
+                            4 => FilePrefix::Parent,
+                            5 => FilePrefix::Home,
+                            _ => Err(DecodeError::WrongFormatError(
+                                "import/local/prefix".to_owned(),
+                            ))?,
+                        };
+                        let path = rest
+                            .map(|s| {
+                                s.as_string().ok_or_else(|| {
+                                    DecodeError::WrongFormatError(
+                                        "import/local/path".to_owned(),
+                                    )
+                                })
+                            })
+                            .collect::<Result<_, _>>()?;
+                        ImportLocation::Local(prefix, path)
+                    }
+                    6 => {
+                        let env = match rest.next() {
+                            Some(String(s)) => s.to_owned(),
+                            _ => Err(DecodeError::WrongFormatError(
+                                "import/env".to_owned(),
+                            ))?,
+                        };
+                        ImportLocation::Env(env)
+                    }
+                    7 => ImportLocation::Missing,
+                    _ => Err(DecodeError::WrongFormatError(
+                        "import/type".to_owned(),
+                    ))?,
+                };
+                Embed(Import {
+                    mode,
+                    location_hashed: ImportHashed { hash, location },
+                })
+            }
+            [U64(25), bindings..] => {
+                let mut tuples = bindings.iter().tuples();
+                let bindings = (&mut tuples)
+                    .map(|(x, t, v)| {
+                        let x = x.as_string().ok_or_else(|| {
+                            DecodeError::WrongFormatError(
+                                "let/label".to_owned(),
+                            )
+                        })?;
+                        let x = Label::from(x.as_str());
+                        let t = match t {
+                            Null => None,
+                            t => Some(cbor_value_to_dhall(&t)?),
+                        };
+                        let v = cbor_value_to_dhall(&v)?;
+                        Ok((x, t, v))
+                    })
+                    .collect::<Result<Vec<_>, _>>()?;
+                let expr = tuples.into_buffer().next().ok_or_else(|| {
+                    DecodeError::WrongFormatError("let/expr".to_owned())
+                })?;
+                let expr = cbor_value_to_dhall(expr)?;
+                return Ok(bindings
+                    .into_iter()
+                    .rev()
+                    .fold(expr, |acc, (x, t, v)| rc(Let(x, t, v, acc))));
+            }
+            [U64(26), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                Annot(x, y)
+            }
+            _ => Err(DecodeError::WrongFormatError(format!("{:?}", data)))?,
+        },
+        _ => Err(DecodeError::WrongFormatError(format!("{:?}", data)))?,
+    }))
+}
+
+fn cbor_map_to_dhall_map(
+    map: &std::collections::BTreeMap<cbor::ObjectKey, cbor::Value>,
+) -> Result<std::collections::BTreeMap<Label, ParsedExpr>, DecodeError> {
+    map.iter()
+        .map(|(k, v)| -> Result<(_, _), _> {
+            let k = k.as_string().ok_or_else(|| {
+                DecodeError::WrongFormatError("map/key".to_owned())
+            })?;
+            let v = cbor_value_to_dhall(v)?;
+            Ok((Label::from(k.as_ref()), v))
+        })
+        .collect::<Result<_, _>>()
+}
+
+fn cbor_map_to_dhall_opt_map(
+    map: &std::collections::BTreeMap<cbor::ObjectKey, cbor::Value>,
+) -> Result<std::collections::BTreeMap<Label, Option<ParsedExpr>>, DecodeError>
+{
+    map.iter()
+        .map(|(k, v)| -> Result<(_, _), _> {
+            let k = k.as_string().ok_or_else(|| {
+                DecodeError::WrongFormatError("map/key".to_owned())
+            })?;
+            let v = match v {
+                cbor::Value::Null => None,
+                _ => Some(cbor_value_to_dhall(v)?),
+            };
+            Ok((Label::from(k.as_ref()), v))
+        })
+        .collect::<Result<_, _>>()
+}
diff --git a/dhall/src/phase/mod.rs b/dhall/src/phase/mod.rs
new file mode 100644
index 0000000..0b6eca6
--- /dev/null
+++ b/dhall/src/phase/mod.rs
@@ -0,0 +1,389 @@
+use std::borrow::Cow;
+use std::fmt::Display;
+use std::path::Path;
+
+use dhall_syntax::{Const, Import, Span, SubExpr, X};
+
+use crate::error::Error;
+
+use normalize::{AlphaVar, Thunk, Value};
+use resolve::{ImportError, ImportRoot};
+use typecheck::{
+    const_to_typed, type_of_const, TypeError, TypeMessage, TypecheckContext,
+};
+
+pub(crate) mod binary;
+pub(crate) mod normalize;
+pub(crate) mod parse;
+pub(crate) mod resolve;
+pub(crate) mod typecheck;
+
+pub(crate) type ParsedSubExpr = SubExpr<Span, Import>;
+pub(crate) type ResolvedSubExpr = SubExpr<Span, Normalized>;
+pub(crate) type NormalizedSubExpr = SubExpr<X, X>;
+
+#[derive(Debug, Clone)]
+pub(crate) struct Parsed(pub(crate) ParsedSubExpr, pub(crate) ImportRoot);
+
+/// An expression where all imports have been resolved
+#[derive(Debug, Clone)]
+pub(crate) struct Resolved(pub(crate) ResolvedSubExpr);
+
+/// A typed expression
+#[derive(Debug, Clone)]
+pub(crate) enum Typed {
+    // The `Sort` higher-kinded type; it doesn't have a type
+    Sort,
+    // Any other value, along with (optionally) its type
+    Value(Thunk, Option<Type>),
+}
+
+/// A normalized expression.
+///
+/// Invariant: the contained Typed expression must be in normal form,
+#[derive(Debug, Clone)]
+pub(crate) struct Normalized(pub(crate) Typed);
+
+/// A Dhall expression representing a simple type.
+///
+/// This captures what is usually simply called a "type", like
+/// `Bool`, `{ x: Integer }` or `Natural -> Text`.
+///
+/// For a more general notion of "type", see [Type].
+#[derive(Debug, Clone)]
+pub struct SimpleType(pub(crate) NormalizedSubExpr);
+
+/// A Dhall expression representing a (possibly higher-kinded) type.
+///
+/// This includes [SimpleType]s but also higher-kinded expressions like
+/// `Type`, `Kind` and `{ x: Type }`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Type(pub(crate) TypeInternal);
+
+#[derive(Debug, Clone)]
+pub(crate) enum TypeInternal {
+    Const(Const),
+    /// This must not contain a Const value.
+    Typed(Box<Typed>),
+}
+
+impl Parsed {
+    pub fn parse_file(f: &Path) -> Result<Parsed, Error> {
+        parse::parse_file(f)
+    }
+
+    pub fn parse_str(s: &str) -> Result<Parsed, Error> {
+        parse::parse_str(s)
+    }
+
+    #[allow(dead_code)]
+    pub fn parse_binary_file(f: &Path) -> Result<Parsed, Error> {
+        parse::parse_binary_file(f)
+    }
+
+    pub fn resolve(self) -> Result<Resolved, ImportError> {
+        resolve::resolve(self)
+    }
+
+    #[allow(dead_code)]
+    pub fn skip_resolve(self) -> Result<Resolved, ImportError> {
+        resolve::skip_resolve_expr(self)
+    }
+}
+
+impl Resolved {
+    pub fn typecheck(self) -> Result<Typed, TypeError> {
+        typecheck::typecheck(self)
+    }
+    pub fn typecheck_with(self, ty: &Type) -> Result<Typed, TypeError> {
+        typecheck::typecheck_with(self, ty)
+    }
+    /// Pretends this expression has been typechecked. Use with care.
+    #[allow(dead_code)]
+    pub fn skip_typecheck(self) -> Typed {
+        typecheck::skip_typecheck(self)
+    }
+}
+
+impl Typed {
+    /// Reduce an expression to its normal form, performing beta reduction
+    ///
+    /// `normalize` does not type-check the expression.  You may want to type-check
+    /// expressions before normalizing them since normalization can convert an
+    /// ill-typed expression into a well-typed expression.
+    ///
+    /// However, `normalize` will not fail if the expression is ill-typed and will
+    /// leave ill-typed sub-expressions unevaluated.
+    pub fn normalize(self) -> Normalized {
+        match &self {
+            Typed::Sort => {}
+            Typed::Value(thunk, _) => {
+                thunk.normalize_nf();
+            }
+        }
+        Normalized(self)
+    }
+
+    pub(crate) fn from_thunk_and_type(th: Thunk, t: Type) -> Self {
+        Typed::Value(th, Some(t))
+    }
+    pub(crate) fn from_thunk_untyped(th: Thunk) -> Self {
+        Typed::Value(th, None)
+    }
+
+    // TODO: Avoid cloning if possible
+    pub(crate) fn to_value(&self) -> Value {
+        match self {
+            Typed::Value(th, _) => th.to_value(),
+            Typed::Sort => Value::Const(Const::Sort),
+        }
+    }
+    pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
+        self.to_value().normalize_to_expr()
+    }
+    pub(crate) fn to_expr_alpha(&self) -> NormalizedSubExpr {
+        self.to_value().normalize_to_expr_maybe_alpha(true)
+    }
+    pub(crate) fn to_thunk(&self) -> Thunk {
+        match self {
+            Typed::Value(th, _) => th.clone(),
+            Typed::Sort => Thunk::from_value(Value::Const(Const::Sort)),
+        }
+    }
+    pub(crate) fn to_type(&self) -> Type {
+        match self {
+            Typed::Sort => Type(TypeInternal::Const(Const::Sort)),
+            Typed::Value(th, _) => match &*th.as_value() {
+                Value::Const(c) => Type(TypeInternal::Const(*c)),
+                _ => Type(TypeInternal::Typed(Box::new(self.clone()))),
+            },
+        }
+    }
+
+    pub(crate) fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        match self {
+            Typed::Value(_, Some(t)) => Ok(Cow::Borrowed(t)),
+            Typed::Value(_, None) => Err(TypeError::new(
+                &TypecheckContext::new(),
+                TypeMessage::Untyped,
+            )),
+            Typed::Sort => {
+                Err(TypeError::new(&TypecheckContext::new(), TypeMessage::Sort))
+            }
+        }
+    }
+
+    pub(crate) fn const_sort() -> Self {
+        Typed::Sort
+    }
+
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        match self {
+            Typed::Value(th, t) => Typed::Value(
+                th.shift(delta, var),
+                t.as_ref().map(|x| x.shift(delta, var)),
+            ),
+            Typed::Sort => Typed::Sort,
+        }
+    }
+
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            Typed::Value(th, t) => Typed::Value(
+                th.subst_shift(var, val),
+                t.as_ref().map(|x| x.subst_shift(var, val)),
+            ),
+            Typed::Sort => Typed::Sort,
+        }
+    }
+}
+
+impl Type {
+    pub(crate) fn to_normalized(&self) -> Normalized {
+        self.0.to_normalized()
+    }
+    pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
+        self.0.to_expr()
+    }
+    pub(crate) fn to_value(&self) -> Value {
+        self.0.to_value()
+    }
+    pub(crate) fn as_const(&self) -> Option<Const> {
+        self.0.as_const()
+    }
+    pub(crate) fn internal_whnf(&self) -> Option<Value> {
+        self.0.whnf()
+    }
+    pub(crate) fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        self.0.get_type()
+    }
+
+    pub(crate) fn const_sort() -> Self {
+        Type(TypeInternal::Const(Const::Sort))
+    }
+    pub(crate) fn const_kind() -> Self {
+        Type(TypeInternal::Const(Const::Kind))
+    }
+    pub(crate) fn const_type() -> Self {
+        Type(TypeInternal::Const(Const::Type))
+    }
+
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        Type(self.0.shift(delta, var))
+    }
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        Type(self.0.subst_shift(var, val))
+    }
+}
+
+impl TypeInternal {
+    pub(crate) fn to_typed(&self) -> Typed {
+        match self {
+            TypeInternal::Typed(e) => e.as_ref().clone(),
+            TypeInternal::Const(c) => const_to_typed(*c),
+        }
+    }
+    pub(crate) fn to_normalized(&self) -> Normalized {
+        self.to_typed().normalize()
+    }
+    pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
+        self.to_normalized().to_expr()
+    }
+    pub(crate) fn to_value(&self) -> Value {
+        self.to_typed().to_value()
+    }
+    pub(crate) fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        Ok(match self {
+            TypeInternal::Typed(e) => e.get_type()?,
+            TypeInternal::Const(c) => Cow::Owned(type_of_const(*c)?),
+        })
+    }
+    pub(crate) fn as_const(&self) -> Option<Const> {
+        match self {
+            TypeInternal::Const(c) => Some(*c),
+            _ => None,
+        }
+    }
+    pub(crate) fn whnf(&self) -> Option<Value> {
+        match self {
+            TypeInternal::Typed(e) => Some(e.to_value()),
+            _ => None,
+        }
+    }
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        use TypeInternal::*;
+        match self {
+            Typed(e) => Typed(Box::new(e.shift(delta, var))),
+            Const(c) => Const(*c),
+        }
+    }
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        use TypeInternal::*;
+        match self {
+            Typed(e) => Typed(Box::new(e.subst_shift(var, val))),
+            Const(c) => Const(*c),
+        }
+    }
+}
+
+impl Normalized {
+    pub(crate) fn from_thunk_and_type(th: Thunk, t: Type) -> Self {
+        Normalized(Typed::from_thunk_and_type(th, t))
+    }
+
+    pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
+        self.0.to_expr()
+    }
+    #[allow(dead_code)]
+    pub(crate) fn to_expr_alpha(&self) -> NormalizedSubExpr {
+        self.0.to_expr_alpha()
+    }
+    pub(crate) fn to_value(&self) -> Value {
+        self.0.to_value()
+    }
+    pub(crate) fn to_thunk(&self) -> Thunk {
+        self.0.to_thunk()
+    }
+    pub(crate) fn to_type(self) -> Type {
+        self.0.to_type()
+    }
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        Normalized(self.0.shift(delta, var))
+    }
+}
+
+macro_rules! derive_traits_for_wrapper_struct {
+    ($ty:ident) => {
+        impl std::cmp::PartialEq for $ty {
+            fn eq(&self, other: &Self) -> bool {
+                self.0 == other.0
+            }
+        }
+
+        impl std::cmp::Eq for $ty {}
+
+        impl std::fmt::Display for $ty {
+            fn fmt(
+                &self,
+                f: &mut std::fmt::Formatter,
+            ) -> Result<(), std::fmt::Error> {
+                self.0.fmt(f)
+            }
+        }
+    };
+}
+
+derive_traits_for_wrapper_struct!(Parsed);
+derive_traits_for_wrapper_struct!(Resolved);
+derive_traits_for_wrapper_struct!(Normalized);
+derive_traits_for_wrapper_struct!(SimpleType);
+
+impl Eq for Typed {}
+impl PartialEq for Typed {
+    fn eq(&self, other: &Self) -> bool {
+        self.to_value() == other.to_value()
+    }
+}
+
+impl Eq for TypeInternal {}
+impl PartialEq for TypeInternal {
+    fn eq(&self, other: &Self) -> bool {
+        self.to_normalized() == other.to_normalized()
+    }
+}
+
+impl Display for Typed {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        self.to_expr().fmt(f)
+    }
+}
+
+impl Display for Type {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        self.to_normalized().fmt(f)
+    }
+}
+
+// Exposed for the macros
+#[doc(hidden)]
+impl From<SimpleType> for NormalizedSubExpr {
+    fn from(x: SimpleType) -> NormalizedSubExpr {
+        x.0
+    }
+}
+
+// Exposed for the macros
+#[doc(hidden)]
+impl From<NormalizedSubExpr> for SimpleType {
+    fn from(x: NormalizedSubExpr) -> SimpleType {
+        SimpleType(x)
+    }
+}
+
+// Exposed for the macros
+#[doc(hidden)]
+impl From<Normalized> for Typed {
+    fn from(x: Normalized) -> Typed {
+        x.0
+    }
+}
diff --git a/dhall/src/phase/normalize.rs b/dhall/src/phase/normalize.rs
new file mode 100644
index 0000000..2340bbd
--- /dev/null
+++ b/dhall/src/phase/normalize.rs
@@ -0,0 +1,1888 @@
+#![allow(non_snake_case)]
+use std::collections::BTreeMap;
+use std::rc::Rc;
+
+use dhall_proc_macros as dhall;
+use dhall_syntax::context::Context;
+use dhall_syntax::{
+    rc, BinOp, Builtin, Const, ExprF, Integer, InterpolatedTextContents, Label,
+    Natural, V, X,
+};
+
+use crate::phase::{NormalizedSubExpr, ResolvedSubExpr, Type, Typed};
+
+type InputSubExpr = ResolvedSubExpr;
+type OutputSubExpr = NormalizedSubExpr;
+
+/// Stores a pair of variables: a normal one and if relevant one
+/// that corresponds to the alpha-normalized version of the first one.
+#[derive(Debug, Clone, Eq)]
+pub(crate) struct AlphaVar {
+    normal: V<Label>,
+    alpha: Option<V<()>>,
+}
+
+impl AlphaVar {
+    pub(crate) fn to_var(&self, alpha: bool) -> V<Label> {
+        match (alpha, &self.alpha) {
+            (true, Some(x)) => V("_".into(), x.1),
+            _ => self.normal.clone(),
+        }
+    }
+    pub(crate) fn from_var(normal: V<Label>) -> Self {
+        AlphaVar {
+            normal,
+            alpha: None,
+        }
+    }
+    pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        AlphaVar {
+            normal: self.normal.shift(delta, &var.normal),
+            alpha: match (&self.alpha, &var.alpha) {
+                (Some(x), Some(v)) => Some(x.shift(delta, v)),
+                _ => None,
+            },
+        }
+    }
+}
+
+/// Equality is up to alpha-equivalence.
+impl std::cmp::PartialEq for AlphaVar {
+    fn eq(&self, other: &Self) -> bool {
+        match (&self.alpha, &other.alpha) {
+            (Some(x), Some(y)) => x == y,
+            (None, None) => self.normal == other.normal,
+            _ => false,
+        }
+    }
+}
+
+impl From<Label> for AlphaVar {
+    fn from(x: Label) -> AlphaVar {
+        AlphaVar {
+            normal: V(x, 0),
+            alpha: Some(V((), 0)),
+        }
+    }
+}
+impl<'a> From<&'a Label> for AlphaVar {
+    fn from(x: &'a Label) -> AlphaVar {
+        x.clone().into()
+    }
+}
+impl From<AlphaLabel> for AlphaVar {
+    fn from(x: AlphaLabel) -> AlphaVar {
+        let l: Label = x.into();
+        l.into()
+    }
+}
+impl<'a> From<&'a AlphaLabel> for AlphaVar {
+    fn from(x: &'a AlphaLabel) -> AlphaVar {
+        x.clone().into()
+    }
+}
+
+// Exactly like a Label, but equality returns always true.
+// This is so that Value equality is exactly alpha-equivalence.
+#[derive(Debug, Clone, Eq)]
+pub(crate) struct AlphaLabel(Label);
+
+impl AlphaLabel {
+    fn to_label_maybe_alpha(&self, alpha: bool) -> Label {
+        if alpha {
+            "_".into()
+        } else {
+            self.to_label()
+        }
+    }
+    fn to_label(&self) -> Label {
+        self.clone().into()
+    }
+}
+
+impl std::cmp::PartialEq for AlphaLabel {
+    fn eq(&self, _other: &Self) -> bool {
+        true
+    }
+}
+
+impl From<Label> for AlphaLabel {
+    fn from(x: Label) -> AlphaLabel {
+        AlphaLabel(x)
+    }
+}
+impl From<AlphaLabel> for Label {
+    fn from(x: AlphaLabel) -> Label {
+        x.0
+    }
+}
+
+#[derive(Debug, Clone)]
+enum EnvItem {
+    Thunk(Thunk),
+    Skip(AlphaVar),
+}
+
+impl EnvItem {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        use EnvItem::*;
+        match self {
+            Thunk(e) => Thunk(e.shift(delta, var)),
+            Skip(v) => Skip(v.shift(delta, var)),
+        }
+    }
+
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            EnvItem::Thunk(e) => EnvItem::Thunk(e.subst_shift(var, val)),
+            EnvItem::Skip(v) if v == var => EnvItem::Thunk(val.to_thunk()),
+            EnvItem::Skip(v) => EnvItem::Skip(v.shift(-1, var)),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct NormalizationContext(Rc<Context<Label, EnvItem>>);
+
+impl NormalizationContext {
+    pub(crate) fn new() -> Self {
+        NormalizationContext(Rc::new(Context::new()))
+    }
+    fn skip(&self, x: &Label) -> Self {
+        NormalizationContext(Rc::new(
+            self.0
+                .map(|_, e| e.shift(1, &x.into()))
+                .insert(x.clone(), EnvItem::Skip(x.into())),
+        ))
+    }
+    fn lookup(&self, var: &V<Label>) -> Value {
+        let V(x, n) = var;
+        match self.0.lookup(x, *n) {
+            Some(EnvItem::Thunk(t)) => t.to_value(),
+            Some(EnvItem::Skip(newvar)) => Value::Var(newvar.clone()),
+            // Free variable
+            None => Value::Var(AlphaVar::from_var(var.clone())),
+        }
+    }
+    pub(crate) fn from_typecheck_ctx(
+        tc_ctx: &crate::phase::typecheck::TypecheckContext,
+    ) -> Self {
+        use crate::phase::typecheck::EnvItem::*;
+        let mut ctx = Context::new();
+        for (k, vs) in tc_ctx.0.iter_keys() {
+            for v in vs.iter() {
+                let new_item = match v {
+                    Type(var, _) => EnvItem::Skip(var.clone()),
+                    Value(e) => EnvItem::Thunk(e.to_thunk()),
+                };
+                ctx = ctx.insert(k.clone(), new_item);
+            }
+        }
+        NormalizationContext(Rc::new(ctx))
+    }
+
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        NormalizationContext(Rc::new(self.0.map(|_, e| e.shift(delta, var))))
+    }
+
+    fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        NormalizationContext(Rc::new(
+            self.0.map(|_, e| e.subst_shift(var, val)),
+        ))
+    }
+}
+
+/// A semantic value.
+/// Equality is up to alpha-equivalence (renaming of bound variables).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum Value {
+    /// Closures
+    Lam(AlphaLabel, Thunk, Thunk),
+    AppliedBuiltin(Builtin, Vec<Thunk>),
+    /// `λ(x: a) -> Some x`
+    OptionalSomeClosure(TypeThunk),
+    /// `λ(x : a) -> λ(xs : List a) -> [ x ] # xs`
+    /// `λ(xs : List a) -> [ x ] # xs`
+    ListConsClosure(TypeThunk, Option<Thunk>),
+    /// `λ(x : Natural) -> x + 1`
+    NaturalSuccClosure,
+    Pi(AlphaLabel, TypeThunk, TypeThunk),
+
+    Var(AlphaVar),
+    Const(Const),
+    BoolLit(bool),
+    NaturalLit(Natural),
+    IntegerLit(Integer),
+    EmptyOptionalLit(TypeThunk),
+    NEOptionalLit(Thunk),
+    EmptyListLit(TypeThunk),
+    NEListLit(Vec<Thunk>),
+    RecordLit(BTreeMap<Label, Thunk>),
+    RecordType(BTreeMap<Label, TypeThunk>),
+    UnionType(BTreeMap<Label, Option<TypeThunk>>),
+    UnionConstructor(Label, BTreeMap<Label, Option<TypeThunk>>),
+    UnionLit(Label, Thunk, BTreeMap<Label, Option<TypeThunk>>),
+    TextLit(Vec<InterpolatedTextContents<Thunk>>),
+    /// Invariant: This must not contain a value captured by one of the variants above.
+    PartialExpr(ExprF<Thunk, Label, X>),
+}
+
+impl Value {
+    pub(crate) fn into_thunk(self) -> Thunk {
+        Thunk::from_value(self)
+    }
+
+    /// Convert the value to a fully normalized syntactic expression
+    pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
+        self.normalize_to_expr_maybe_alpha(false)
+    }
+    /// Convert the value to a fully normalized syntactic expression. Also alpha-normalize
+    /// if alpha is `true`
+    pub(crate) fn normalize_to_expr_maybe_alpha(
+        &self,
+        alpha: bool,
+    ) -> OutputSubExpr {
+        match self {
+            Value::Lam(x, t, e) => rc(ExprF::Lam(
+                x.to_label_maybe_alpha(alpha),
+                t.normalize_to_expr_maybe_alpha(alpha),
+                e.normalize_to_expr_maybe_alpha(alpha),
+            )),
+            Value::AppliedBuiltin(b, args) => {
+                let mut e = rc(ExprF::Builtin(*b));
+                for v in args {
+                    e = rc(ExprF::App(
+                        e,
+                        v.normalize_to_expr_maybe_alpha(alpha),
+                    ));
+                }
+                e
+            }
+            Value::OptionalSomeClosure(n) => {
+                let a = n.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(x: a) -> Some x)
+            }
+            Value::ListConsClosure(a, None) => {
+                // Avoid accidental capture of the new `x` variable
+                let a1 = a.shift(1, &Label::from("x").into());
+                let a1 = a1.normalize_to_expr_maybe_alpha(alpha);
+                let a = a.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(x : a) -> λ(xs : List a1) -> [ x ] # xs)
+            }
+            Value::ListConsClosure(n, Some(v)) => {
+                // Avoid accidental capture of the new `xs` variable
+                let v = v.shift(1, &Label::from("xs").into());
+                let v = v.normalize_to_expr_maybe_alpha(alpha);
+                let a = n.normalize_to_expr_maybe_alpha(alpha);
+                dhall::subexpr!(λ(xs : List a) -> [ v ] # xs)
+            }
+            Value::NaturalSuccClosure => {
+                dhall::subexpr!(λ(x : Natural) -> x + 1)
+            }
+            Value::Pi(x, t, e) => rc(ExprF::Pi(
+                x.to_label_maybe_alpha(alpha),
+                t.normalize_to_expr_maybe_alpha(alpha),
+                e.normalize_to_expr_maybe_alpha(alpha),
+            )),
+            Value::Var(v) => rc(ExprF::Var(v.to_var(alpha))),
+            Value::Const(c) => rc(ExprF::Const(*c)),
+            Value::BoolLit(b) => rc(ExprF::BoolLit(*b)),
+            Value::NaturalLit(n) => rc(ExprF::NaturalLit(*n)),
+            Value::IntegerLit(n) => rc(ExprF::IntegerLit(*n)),
+            Value::EmptyOptionalLit(n) => rc(ExprF::App(
+                rc(ExprF::Builtin(Builtin::OptionalNone)),
+                n.normalize_to_expr_maybe_alpha(alpha),
+            )),
+            Value::NEOptionalLit(n) => {
+                rc(ExprF::SomeLit(n.normalize_to_expr_maybe_alpha(alpha)))
+            }
+            Value::EmptyListLit(n) => {
+                rc(ExprF::EmptyListLit(n.normalize_to_expr_maybe_alpha(alpha)))
+            }
+            Value::NEListLit(elts) => rc(ExprF::NEListLit(
+                elts.into_iter()
+                    .map(|n| n.normalize_to_expr_maybe_alpha(alpha))
+                    .collect(),
+            )),
+            Value::RecordLit(kvs) => rc(ExprF::RecordLit(
+                kvs.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.normalize_to_expr_maybe_alpha(alpha))
+                    })
+                    .collect(),
+            )),
+            Value::RecordType(kts) => rc(ExprF::RecordType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.normalize_to_expr_maybe_alpha(alpha))
+                    })
+                    .collect(),
+            )),
+            Value::UnionType(kts) => rc(ExprF::UnionType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect(),
+            )),
+            Value::UnionConstructor(l, kts) => {
+                let kts = kts
+                    .iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect();
+                rc(ExprF::Field(rc(ExprF::UnionType(kts)), l.clone()))
+            }
+            Value::UnionLit(l, v, kts) => rc(ExprF::UnionLit(
+                l.clone(),
+                v.normalize_to_expr_maybe_alpha(alpha),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (
+                            k.clone(),
+                            v.as_ref().map(|v| {
+                                v.normalize_to_expr_maybe_alpha(alpha)
+                            }),
+                        )
+                    })
+                    .collect(),
+            )),
+            Value::TextLit(elts) => {
+                use InterpolatedTextContents::{Expr, Text};
+                rc(ExprF::TextLit(
+                    elts.iter()
+                        .map(|contents| match contents {
+                            Expr(e) => {
+                                Expr(e.normalize_to_expr_maybe_alpha(alpha))
+                            }
+                            Text(s) => Text(s.clone()),
+                        })
+                        .collect(),
+                ))
+            }
+            Value::PartialExpr(e) => {
+                rc(e.map_ref_simple(|v| v.normalize_to_expr_maybe_alpha(alpha)))
+            }
+        }
+    }
+
+    // Deprecated
+    fn normalize(&self) -> Value {
+        let mut v = self.clone();
+        v.normalize_mut();
+        v
+    }
+
+    pub(crate) fn normalize_mut(&mut self) {
+        match self {
+            Value::NaturalSuccClosure
+            | Value::Var(_)
+            | Value::Const(_)
+            | Value::BoolLit(_)
+            | Value::NaturalLit(_)
+            | Value::IntegerLit(_) => {}
+
+            Value::EmptyOptionalLit(tth)
+            | Value::OptionalSomeClosure(tth)
+            | Value::EmptyListLit(tth) => {
+                tth.normalize_mut();
+            }
+
+            Value::NEOptionalLit(th) => {
+                th.normalize_mut();
+            }
+            Value::Lam(_, t, e) => {
+                t.normalize_mut();
+                e.normalize_mut();
+            }
+            Value::Pi(_, t, e) => {
+                t.normalize_mut();
+                e.normalize_mut();
+            }
+            Value::AppliedBuiltin(_, args) => {
+                for x in args.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::ListConsClosure(t, v) => {
+                t.normalize_mut();
+                for x in v.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::NEListLit(elts) => {
+                for x in elts.iter_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::RecordLit(kvs) => {
+                for x in kvs.values_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::RecordType(kvs) => {
+                for x in kvs.values_mut() {
+                    x.normalize_mut();
+                }
+            }
+            Value::UnionType(kts) | Value::UnionConstructor(_, kts) => {
+                for x in kts.values_mut().flat_map(|opt| opt) {
+                    x.normalize_mut();
+                }
+            }
+            Value::UnionLit(_, v, kts) => {
+                v.normalize_mut();
+                for x in kts.values_mut().flat_map(|opt| opt) {
+                    x.normalize_mut();
+                }
+            }
+            Value::TextLit(elts) => {
+                for x in elts.iter_mut() {
+                    use InterpolatedTextContents::{Expr, Text};
+                    match x {
+                        Expr(n) => n.normalize_mut(),
+                        Text(_) => {}
+                    }
+                }
+            }
+            Value::PartialExpr(e) => {
+                // TODO: need map_mut_simple
+                e.map_ref_simple(|v| {
+                    v.normalize_nf();
+                });
+            }
+        }
+    }
+
+    /// Apply to a value
+    pub(crate) fn app(self, val: Value) -> Value {
+        self.app_val(val)
+    }
+
+    /// Apply to a value
+    pub(crate) fn app_val(self, val: Value) -> Value {
+        self.app_thunk(val.into_thunk())
+    }
+
+    /// Apply to a thunk
+    pub(crate) fn app_thunk(self, th: Thunk) -> Value {
+        Thunk::from_value(self).app_thunk(th)
+    }
+
+    pub(crate) fn from_builtin(b: Builtin) -> Value {
+        Value::AppliedBuiltin(b, vec![])
+    }
+
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        match self {
+            Value::Lam(x, t, e) => Value::Lam(
+                x.clone(),
+                t.shift(delta, var),
+                e.shift(delta, &var.shift(1, &x.into())),
+            ),
+            Value::AppliedBuiltin(b, args) => Value::AppliedBuiltin(
+                *b,
+                args.iter().map(|v| v.shift(delta, var)).collect(),
+            ),
+            Value::NaturalSuccClosure => Value::NaturalSuccClosure,
+            Value::OptionalSomeClosure(tth) => {
+                Value::OptionalSomeClosure(tth.shift(delta, var))
+            }
+            Value::ListConsClosure(t, v) => Value::ListConsClosure(
+                t.shift(delta, var),
+                v.as_ref().map(|v| v.shift(delta, var)),
+            ),
+            Value::Pi(x, t, e) => Value::Pi(
+                x.clone(),
+                t.shift(delta, var),
+                e.shift(delta, &var.shift(1, &x.into())),
+            ),
+            Value::Var(v) => Value::Var(v.shift(delta, var)),
+            Value::Const(c) => Value::Const(*c),
+            Value::BoolLit(b) => Value::BoolLit(*b),
+            Value::NaturalLit(n) => Value::NaturalLit(*n),
+            Value::IntegerLit(n) => Value::IntegerLit(*n),
+            Value::EmptyOptionalLit(tth) => {
+                Value::EmptyOptionalLit(tth.shift(delta, var))
+            }
+            Value::NEOptionalLit(th) => {
+                Value::NEOptionalLit(th.shift(delta, var))
+            }
+            Value::EmptyListLit(tth) => {
+                Value::EmptyListLit(tth.shift(delta, var))
+            }
+            Value::NEListLit(elts) => Value::NEListLit(
+                elts.iter().map(|v| v.shift(delta, var)).collect(),
+            ),
+            Value::RecordLit(kvs) => Value::RecordLit(
+                kvs.iter()
+                    .map(|(k, v)| (k.clone(), v.shift(delta, var)))
+                    .collect(),
+            ),
+            Value::RecordType(kvs) => Value::RecordType(
+                kvs.iter()
+                    .map(|(k, v)| (k.clone(), v.shift(delta, var)))
+                    .collect(),
+            ),
+            Value::UnionType(kts) => Value::UnionType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+                    })
+                    .collect(),
+            ),
+            Value::UnionConstructor(x, kts) => Value::UnionConstructor(
+                x.clone(),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+                    })
+                    .collect(),
+            ),
+            Value::UnionLit(x, v, kts) => Value::UnionLit(
+                x.clone(),
+                v.shift(delta, var),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.shift(delta, var)))
+                    })
+                    .collect(),
+            ),
+            Value::TextLit(elts) => Value::TextLit(
+                elts.iter()
+                    .map(|contents| {
+                        use InterpolatedTextContents::{Expr, Text};
+                        match contents {
+                            Expr(th) => Expr(th.shift(delta, var)),
+                            Text(s) => Text(s.clone()),
+                        }
+                    })
+                    .collect(),
+            ),
+            Value::PartialExpr(e) => {
+                Value::PartialExpr(e.map_ref_with_special_handling_of_binders(
+                    |v| v.shift(delta, var),
+                    |x, v| v.shift(delta, &var.shift(1, &x.into())),
+                    X::clone,
+                    Label::clone,
+                ))
+            }
+        }
+    }
+
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            // Retry normalizing since substituting may allow progress
+            Value::AppliedBuiltin(b, args) => apply_builtin(
+                *b,
+                args.iter().map(|v| v.subst_shift(var, val)).collect(),
+            ),
+            // Retry normalizing since substituting may allow progress
+            Value::PartialExpr(e) => {
+                normalize_one_layer(e.map_ref_with_special_handling_of_binders(
+                    |v| v.subst_shift(var, val),
+                    |x, v| {
+                        v.subst_shift(
+                            &var.shift(1, &x.into()),
+                            &val.shift(1, &x.into()),
+                        )
+                    },
+                    X::clone,
+                    Label::clone,
+                ))
+            }
+            // Retry normalizing since substituting may allow progress
+            Value::TextLit(elts) => {
+                Value::TextLit(squash_textlit(elts.iter().map(|contents| {
+                    use InterpolatedTextContents::{Expr, Text};
+                    match contents {
+                        Expr(th) => Expr(th.subst_shift(var, val)),
+                        Text(s) => Text(s.clone()),
+                    }
+                })))
+            }
+            Value::Lam(x, t, e) => Value::Lam(
+                x.clone(),
+                t.subst_shift(var, val),
+                e.subst_shift(
+                    &var.shift(1, &x.into()),
+                    &val.shift(1, &x.into()),
+                ),
+            ),
+            Value::NaturalSuccClosure => Value::NaturalSuccClosure,
+            Value::OptionalSomeClosure(tth) => {
+                Value::OptionalSomeClosure(tth.subst_shift(var, val))
+            }
+            Value::ListConsClosure(t, v) => Value::ListConsClosure(
+                t.subst_shift(var, val),
+                v.as_ref().map(|v| v.subst_shift(var, val)),
+            ),
+            Value::Pi(x, t, e) => Value::Pi(
+                x.clone(),
+                t.subst_shift(var, val),
+                e.subst_shift(
+                    &var.shift(1, &x.into()),
+                    &val.shift(1, &x.into()),
+                ),
+            ),
+            Value::Var(v) if v == var => val.to_value().clone(),
+            Value::Var(v) => Value::Var(v.shift(-1, var)),
+            Value::Const(c) => Value::Const(*c),
+            Value::BoolLit(b) => Value::BoolLit(*b),
+            Value::NaturalLit(n) => Value::NaturalLit(*n),
+            Value::IntegerLit(n) => Value::IntegerLit(*n),
+            Value::EmptyOptionalLit(tth) => {
+                Value::EmptyOptionalLit(tth.subst_shift(var, val))
+            }
+            Value::NEOptionalLit(th) => {
+                Value::NEOptionalLit(th.subst_shift(var, val))
+            }
+            Value::EmptyListLit(tth) => {
+                Value::EmptyListLit(tth.subst_shift(var, val))
+            }
+            Value::NEListLit(elts) => Value::NEListLit(
+                elts.iter().map(|v| v.subst_shift(var, val)).collect(),
+            ),
+            Value::RecordLit(kvs) => Value::RecordLit(
+                kvs.iter()
+                    .map(|(k, v)| (k.clone(), v.subst_shift(var, val)))
+                    .collect(),
+            ),
+            Value::RecordType(kvs) => Value::RecordType(
+                kvs.iter()
+                    .map(|(k, v)| (k.clone(), v.subst_shift(var, val)))
+                    .collect(),
+            ),
+            Value::UnionType(kts) => Value::UnionType(
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+                    })
+                    .collect(),
+            ),
+            Value::UnionConstructor(x, kts) => Value::UnionConstructor(
+                x.clone(),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+                    })
+                    .collect(),
+            ),
+            Value::UnionLit(x, v, kts) => Value::UnionLit(
+                x.clone(),
+                v.subst_shift(var, val),
+                kts.iter()
+                    .map(|(k, v)| {
+                        (k.clone(), v.as_ref().map(|v| v.subst_shift(var, val)))
+                    })
+                    .collect(),
+            ),
+        }
+    }
+}
+
+mod thunk {
+    use super::{
+        apply_any, normalize_whnf, AlphaVar, InputSubExpr,
+        NormalizationContext, OutputSubExpr, Value,
+    };
+    use crate::phase::Typed;
+    use std::cell::{Ref, RefCell};
+    use std::rc::Rc;
+
+    #[derive(Debug, Clone, Copy)]
+    enum Marker {
+        /// Weak Head Normal Form, i.e. subexpressions may not be normalized
+        WHNF,
+        /// Normal form, i.e. completely normalized
+        NF,
+    }
+    use Marker::{NF, WHNF};
+
+    #[derive(Debug)]
+    enum ThunkInternal {
+        /// Non-normalized value alongside a normalization context
+        Unnormalized(NormalizationContext, InputSubExpr),
+        /// Partially normalized value.
+        /// Invariant: if the marker is `NF`, the value must be fully normalized
+        Value(Marker, Value),
+    }
+
+    /// Stores a possibl unevaluated value. Uses RefCell to ensure that
+    /// the value gets normalized at most once.
+    #[derive(Debug, Clone)]
+    pub struct Thunk(Rc<RefCell<ThunkInternal>>);
+
+    impl ThunkInternal {
+        fn into_thunk(self) -> Thunk {
+            Thunk(Rc::new(RefCell::new(self)))
+        }
+
+        fn normalize_whnf(&mut self) {
+            match self {
+                ThunkInternal::Unnormalized(ctx, e) => {
+                    *self = ThunkInternal::Value(
+                        WHNF,
+                        normalize_whnf(ctx.clone(), e.clone()),
+                    )
+                }
+                // Already at least in WHNF
+                ThunkInternal::Value(_, _) => {}
+            }
+        }
+
+        fn normalize_nf(&mut self) {
+            match self {
+                ThunkInternal::Unnormalized(_, _) => {
+                    self.normalize_whnf();
+                    self.normalize_nf();
+                }
+                ThunkInternal::Value(m @ WHNF, v) => {
+                    v.normalize_mut();
+                    *m = NF;
+                }
+                // Already in NF
+                ThunkInternal::Value(NF, _) => {}
+            }
+        }
+
+        // Always use normalize_whnf before
+        fn as_whnf(&self) -> &Value {
+            match self {
+                ThunkInternal::Unnormalized(_, _) => unreachable!(),
+                ThunkInternal::Value(_, v) => v,
+            }
+        }
+
+        // Always use normalize_nf before
+        fn as_nf(&self) -> &Value {
+            match self {
+                ThunkInternal::Unnormalized(_, _) => unreachable!(),
+                ThunkInternal::Value(WHNF, _) => unreachable!(),
+                ThunkInternal::Value(NF, v) => v,
+            }
+        }
+
+        fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+            match self {
+                ThunkInternal::Unnormalized(ctx, e) => {
+                    ThunkInternal::Unnormalized(
+                        ctx.shift(delta, var),
+                        e.clone(),
+                    )
+                }
+                ThunkInternal::Value(m, v) => {
+                    ThunkInternal::Value(*m, v.shift(delta, var))
+                }
+            }
+        }
+
+        fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+            match self {
+                ThunkInternal::Unnormalized(ctx, e) => {
+                    ThunkInternal::Unnormalized(
+                        ctx.subst_shift(var, val),
+                        e.clone(),
+                    )
+                }
+                ThunkInternal::Value(_, v) => {
+                    // The resulting value may not stay in normal form after substitution
+                    ThunkInternal::Value(WHNF, v.subst_shift(var, val))
+                }
+            }
+        }
+    }
+
+    impl Thunk {
+        pub(crate) fn new(ctx: NormalizationContext, e: InputSubExpr) -> Thunk {
+            ThunkInternal::Unnormalized(ctx, e).into_thunk()
+        }
+
+        pub(crate) fn from_value(v: Value) -> Thunk {
+            ThunkInternal::Value(WHNF, v).into_thunk()
+        }
+
+        pub(crate) fn from_normalized_expr(e: OutputSubExpr) -> Thunk {
+            Thunk::new(
+                NormalizationContext::new(),
+                e.embed_absurd().note_absurd(),
+            )
+        }
+
+        // Normalizes contents to normal form; faster than `normalize_nf` if
+        // no one else shares this thunk
+        pub(crate) fn normalize_mut(&mut self) {
+            match Rc::get_mut(&mut self.0) {
+                // Mutate directly if sole owner
+                Some(refcell) => RefCell::get_mut(refcell).normalize_nf(),
+                // Otherwise mutate through the refcell
+                None => self.0.borrow_mut().normalize_nf(),
+            }
+        }
+
+        fn do_normalize_whnf(&self) {
+            let borrow = self.0.borrow();
+            match &*borrow {
+                ThunkInternal::Unnormalized(_, _) => {
+                    drop(borrow);
+                    self.0.borrow_mut().normalize_whnf();
+                }
+                // Already at least in WHNF
+                ThunkInternal::Value(_, _) => {}
+            }
+        }
+
+        fn do_normalize_nf(&self) {
+            let borrow = self.0.borrow();
+            match &*borrow {
+                ThunkInternal::Unnormalized(_, _)
+                | ThunkInternal::Value(WHNF, _) => {
+                    drop(borrow);
+                    self.0.borrow_mut().normalize_nf();
+                }
+                // Already in NF
+                ThunkInternal::Value(NF, _) => {}
+            }
+        }
+
+        // WARNING: avoid normalizing any thunk while holding on to this ref
+        // or you could run into BorrowMut panics
+        pub(crate) fn normalize_nf(&self) -> Ref<Value> {
+            self.do_normalize_nf();
+            Ref::map(self.0.borrow(), ThunkInternal::as_nf)
+        }
+
+        // WARNING: avoid normalizing any thunk while holding on to this ref
+        // or you could run into BorrowMut panics
+        pub(crate) fn as_value(&self) -> Ref<Value> {
+            self.do_normalize_whnf();
+            Ref::map(self.0.borrow(), ThunkInternal::as_whnf)
+        }
+
+        pub(crate) fn to_value(&self) -> Value {
+            self.as_value().clone()
+        }
+
+        pub(crate) fn normalize_to_expr(&self) -> OutputSubExpr {
+            self.normalize_to_expr_maybe_alpha(false)
+        }
+
+        pub(crate) fn normalize_to_expr_maybe_alpha(
+            &self,
+            alpha: bool,
+        ) -> OutputSubExpr {
+            self.normalize_nf().normalize_to_expr_maybe_alpha(alpha)
+        }
+
+        pub(crate) fn app_val(&self, val: Value) -> Value {
+            self.app_thunk(val.into_thunk())
+        }
+
+        pub(crate) fn app_thunk(&self, th: Thunk) -> Value {
+            apply_any(self.clone(), th)
+        }
+
+        pub(crate) fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+            self.0.borrow().shift(delta, var).into_thunk()
+        }
+
+        pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+            self.0.borrow().subst_shift(var, val).into_thunk()
+        }
+    }
+
+    impl std::cmp::PartialEq for Thunk {
+        fn eq(&self, other: &Self) -> bool {
+            &*self.as_value() == &*other.as_value()
+        }
+    }
+    impl std::cmp::Eq for Thunk {}
+}
+
+pub(crate) use thunk::Thunk;
+
+/// A thunk in type position.
+#[derive(Debug, Clone)]
+pub(crate) enum TypeThunk {
+    Thunk(Thunk),
+    Type(Type),
+}
+
+impl TypeThunk {
+    fn from_value(v: Value) -> TypeThunk {
+        TypeThunk::from_thunk(Thunk::from_value(v))
+    }
+
+    fn from_thunk(th: Thunk) -> TypeThunk {
+        TypeThunk::Thunk(th)
+    }
+
+    pub(crate) fn from_type(t: Type) -> TypeThunk {
+        TypeThunk::Type(t)
+    }
+
+    fn normalize_mut(&mut self) {
+        match self {
+            TypeThunk::Thunk(th) => th.normalize_mut(),
+            TypeThunk::Type(_) => {}
+        }
+    }
+
+    pub(crate) fn normalize_nf(&self) -> Value {
+        match self {
+            TypeThunk::Thunk(th) => th.normalize_nf().clone(),
+            TypeThunk::Type(t) => t.to_value().normalize(),
+        }
+    }
+
+    pub(crate) fn to_value(&self) -> Value {
+        match self {
+            TypeThunk::Thunk(th) => th.to_value(),
+            TypeThunk::Type(t) => t.to_value(),
+        }
+    }
+
+    pub(crate) fn normalize_to_expr_maybe_alpha(
+        &self,
+        alpha: bool,
+    ) -> OutputSubExpr {
+        self.normalize_nf().normalize_to_expr_maybe_alpha(alpha)
+    }
+
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        match self {
+            TypeThunk::Thunk(th) => TypeThunk::Thunk(th.shift(delta, var)),
+            TypeThunk::Type(t) => TypeThunk::Type(t.shift(delta, var)),
+        }
+    }
+
+    pub(crate) fn subst_shift(&self, var: &AlphaVar, val: &Typed) -> Self {
+        match self {
+            TypeThunk::Thunk(th) => TypeThunk::Thunk(th.subst_shift(var, val)),
+            TypeThunk::Type(t) => TypeThunk::Type(t.subst_shift(var, val)),
+        }
+    }
+}
+
+impl std::cmp::PartialEq for TypeThunk {
+    fn eq(&self, other: &Self) -> bool {
+        self.to_value() == other.to_value()
+    }
+}
+impl std::cmp::Eq for TypeThunk {}
+
+fn apply_builtin(b: Builtin, args: Vec<Thunk>) -> Value {
+    use dhall_syntax::Builtin::*;
+    use Value::*;
+
+    // Return Ok((unconsumed args, returned value)), or Err(()) if value could not be produced.
+    let ret = match (b, args.as_slice()) {
+        (OptionalNone, [t, r..]) => {
+            Ok((r, EmptyOptionalLit(TypeThunk::from_thunk(t.clone()))))
+        }
+        (NaturalIsZero, [n, r..]) => match &*n.as_value() {
+            NaturalLit(n) => Ok((r, BoolLit(*n == 0))),
+            _ => Err(()),
+        },
+        (NaturalEven, [n, r..]) => match &*n.as_value() {
+            NaturalLit(n) => Ok((r, BoolLit(*n % 2 == 0))),
+            _ => Err(()),
+        },
+        (NaturalOdd, [n, r..]) => match &*n.as_value() {
+            NaturalLit(n) => Ok((r, BoolLit(*n % 2 != 0))),
+            _ => Err(()),
+        },
+        (NaturalToInteger, [n, r..]) => match &*n.as_value() {
+            NaturalLit(n) => Ok((r, IntegerLit(*n as isize))),
+            _ => Err(()),
+        },
+        (NaturalShow, [n, r..]) => match &*n.as_value() {
+            NaturalLit(n) => Ok((
+                r,
+                TextLit(vec![InterpolatedTextContents::Text(n.to_string())]),
+            )),
+            _ => Err(()),
+        },
+        (ListLength, [_, l, r..]) => match &*l.as_value() {
+            EmptyListLit(_) => Ok((r, NaturalLit(0))),
+            NEListLit(xs) => Ok((r, NaturalLit(xs.len()))),
+            _ => Err(()),
+        },
+        (ListHead, [_, l, r..]) => match &*l.as_value() {
+            EmptyListLit(n) => Ok((r, EmptyOptionalLit(n.clone()))),
+            NEListLit(xs) => {
+                Ok((r, NEOptionalLit(xs.iter().next().unwrap().clone())))
+            }
+            _ => Err(()),
+        },
+        (ListLast, [_, l, r..]) => match &*l.as_value() {
+            EmptyListLit(n) => Ok((r, EmptyOptionalLit(n.clone()))),
+            NEListLit(xs) => {
+                Ok((r, NEOptionalLit(xs.iter().rev().next().unwrap().clone())))
+            }
+            _ => Err(()),
+        },
+        (ListReverse, [_, l, r..]) => match &*l.as_value() {
+            EmptyListLit(n) => Ok((r, EmptyListLit(n.clone()))),
+            NEListLit(xs) => {
+                Ok((r, NEListLit(xs.iter().rev().cloned().collect())))
+            }
+            _ => Err(()),
+        },
+        (ListIndexed, [_, l, r..]) => match &*l.as_value() {
+            EmptyListLit(t) => {
+                let mut kts = BTreeMap::new();
+                kts.insert(
+                    "index".into(),
+                    TypeThunk::from_value(Value::from_builtin(Natural)),
+                );
+                kts.insert("value".into(), t.clone());
+                Ok((r, EmptyListLit(TypeThunk::from_value(RecordType(kts)))))
+            }
+            NEListLit(xs) => {
+                let xs = xs
+                    .iter()
+                    .enumerate()
+                    .map(|(i, e)| {
+                        let i = NaturalLit(i);
+                        let mut kvs = BTreeMap::new();
+                        kvs.insert("index".into(), Thunk::from_value(i));
+                        kvs.insert("value".into(), e.clone());
+                        Thunk::from_value(RecordLit(kvs))
+                    })
+                    .collect();
+                Ok((r, NEListLit(xs)))
+            }
+            _ => Err(()),
+        },
+        (ListBuild, [t, f, r..]) => match &*f.as_value() {
+            // fold/build fusion
+            Value::AppliedBuiltin(ListFold, args) => {
+                if args.len() >= 2 {
+                    Ok((r, args[1].to_value()))
+                } else {
+                    // Do we really need to handle this case ?
+                    unimplemented!()
+                }
+            }
+            _ => Ok((
+                r,
+                f.app_val(Value::from_builtin(List).app_thunk(t.clone()))
+                    .app_val(ListConsClosure(
+                        TypeThunk::from_thunk(t.clone()),
+                        None,
+                    ))
+                    .app_val(EmptyListLit(TypeThunk::from_thunk(t.clone()))),
+            )),
+        },
+        (ListFold, [_, l, _, cons, nil, r..]) => match &*l.as_value() {
+            EmptyListLit(_) => Ok((r, nil.to_value())),
+            NEListLit(xs) => {
+                let mut v = nil.clone();
+                for x in xs.iter().rev() {
+                    v = cons
+                        .clone()
+                        .app_thunk(x.clone())
+                        .app_thunk(v)
+                        .into_thunk();
+                }
+                Ok((r, v.to_value()))
+            }
+            _ => Err(()),
+        },
+        (OptionalBuild, [t, f, r..]) => match &*f.as_value() {
+            // fold/build fusion
+            Value::AppliedBuiltin(OptionalFold, args) => {
+                if args.len() >= 2 {
+                    Ok((r, args[1].to_value()))
+                } else {
+                    // Do we really need to handle this case ?
+                    unimplemented!()
+                }
+            }
+            _ => Ok((
+                r,
+                f.app_val(Value::from_builtin(Optional).app_thunk(t.clone()))
+                    .app_val(OptionalSomeClosure(TypeThunk::from_thunk(
+                        t.clone(),
+                    )))
+                    .app_val(EmptyOptionalLit(TypeThunk::from_thunk(
+                        t.clone(),
+                    ))),
+            )),
+        },
+        (OptionalFold, [_, v, _, just, nothing, r..]) => match &*v.as_value() {
+            EmptyOptionalLit(_) => Ok((r, nothing.to_value())),
+            NEOptionalLit(x) => Ok((r, just.app_thunk(x.clone()))),
+            _ => Err(()),
+        },
+        (NaturalBuild, [f, r..]) => match &*f.as_value() {
+            // fold/build fusion
+            Value::AppliedBuiltin(NaturalFold, args) => {
+                if args.len() >= 1 {
+                    Ok((r, args[0].to_value()))
+                } else {
+                    // Do we really need to handle this case ?
+                    unimplemented!()
+                }
+            }
+            _ => Ok((
+                r,
+                f.app_val(Value::from_builtin(Natural))
+                    .app_val(NaturalSuccClosure)
+                    .app_val(NaturalLit(0)),
+            )),
+        },
+        (NaturalFold, [n, t, succ, zero, r..]) => match &*n.as_value() {
+            NaturalLit(0) => Ok((r, zero.to_value())),
+            NaturalLit(n) => {
+                let fold = Value::from_builtin(NaturalFold)
+                    .app(NaturalLit(n - 1))
+                    .app_thunk(t.clone())
+                    .app_thunk(succ.clone())
+                    .app_thunk(zero.clone());
+                Ok((r, succ.app_val(fold)))
+            }
+            _ => Err(()),
+        },
+        _ => Err(()),
+    };
+    match ret {
+        Ok((unconsumed_args, mut v)) => {
+            let n_consumed_args = args.len() - unconsumed_args.len();
+            for x in args.into_iter().skip(n_consumed_args) {
+                v = v.app_thunk(x);
+            }
+            v
+        }
+        Err(()) => AppliedBuiltin(b, args),
+    }
+}
+
+fn apply_any(f: Thunk, a: Thunk) -> Value {
+    let fallback = |f: Thunk, a: Thunk| Value::PartialExpr(ExprF::App(f, a));
+
+    let f_borrow = f.as_value();
+    match &*f_borrow {
+        Value::Lam(x, _, e) => {
+            let val = Typed::from_thunk_untyped(a);
+            e.subst_shift(&x.into(), &val).to_value()
+        }
+        Value::AppliedBuiltin(b, args) => {
+            use std::iter::once;
+            let args = args.iter().cloned().chain(once(a.clone())).collect();
+            apply_builtin(*b, args)
+        }
+        Value::OptionalSomeClosure(_) => Value::NEOptionalLit(a),
+        Value::ListConsClosure(t, None) => {
+            Value::ListConsClosure(t.clone(), Some(a))
+        }
+        Value::ListConsClosure(_, Some(x)) => {
+            let a_borrow = a.as_value();
+            match &*a_borrow {
+                Value::EmptyListLit(_) => Value::NEListLit(vec![x.clone()]),
+                Value::NEListLit(xs) => {
+                    use std::iter::once;
+                    let xs =
+                        once(x.clone()).chain(xs.iter().cloned()).collect();
+                    Value::NEListLit(xs)
+                }
+                _ => {
+                    drop(f_borrow);
+                    drop(a_borrow);
+                    fallback(f, a)
+                }
+            }
+        }
+        Value::NaturalSuccClosure => {
+            let a_borrow = a.as_value();
+            match &*a_borrow {
+                Value::NaturalLit(n) => Value::NaturalLit(n + 1),
+                _ => {
+                    drop(f_borrow);
+                    drop(a_borrow);
+                    fallback(f, a)
+                }
+            }
+        }
+        Value::UnionConstructor(l, kts) => {
+            Value::UnionLit(l.clone(), a, kts.clone())
+        }
+        _ => {
+            drop(f_borrow);
+            fallback(f, a)
+        }
+    }
+}
+
+fn squash_textlit(
+    elts: impl Iterator<Item = InterpolatedTextContents<Thunk>>,
+) -> Vec<InterpolatedTextContents<Thunk>> {
+    use std::mem::replace;
+    use InterpolatedTextContents::{Expr, Text};
+
+    fn inner(
+        elts: impl Iterator<Item = InterpolatedTextContents<Thunk>>,
+        crnt_str: &mut String,
+        ret: &mut Vec<InterpolatedTextContents<Thunk>>,
+    ) {
+        for contents in elts {
+            match contents {
+                Text(s) => crnt_str.push_str(&s),
+                Expr(e) => {
+                    let e_borrow = e.as_value();
+                    match &*e_borrow {
+                        Value::TextLit(elts2) => {
+                            inner(elts2.iter().cloned(), crnt_str, ret)
+                        }
+                        _ => {
+                            drop(e_borrow);
+                            if !crnt_str.is_empty() {
+                                ret.push(Text(replace(crnt_str, String::new())))
+                            }
+                            ret.push(Expr(e.clone()))
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    let mut crnt_str = String::new();
+    let mut ret = Vec::new();
+    inner(elts, &mut crnt_str, &mut ret);
+    if !crnt_str.is_empty() {
+        ret.push(Text(replace(&mut crnt_str, String::new())))
+    }
+    ret
+}
+
+/// Reduces the imput expression to a Value. Evaluates as little as possible.
+fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> Value {
+    match expr.as_ref() {
+        ExprF::Embed(e) => return e.to_value(),
+        ExprF::Var(v) => return ctx.lookup(v),
+        _ => {}
+    }
+
+    // Thunk subexpressions
+    let expr: ExprF<Thunk, Label, X> =
+        expr.as_ref().map_ref_with_special_handling_of_binders(
+            |e| Thunk::new(ctx.clone(), e.clone()),
+            |x, e| Thunk::new(ctx.skip(x), e.clone()),
+            |_| unreachable!(),
+            Label::clone,
+        );
+
+    normalize_one_layer(expr)
+}
+
+fn normalize_one_layer(expr: ExprF<Thunk, Label, X>) -> Value {
+    use Value::{
+        BoolLit, EmptyListLit, EmptyOptionalLit, IntegerLit, Lam, NEListLit,
+        NEOptionalLit, NaturalLit, Pi, RecordLit, RecordType, TextLit,
+        UnionConstructor, UnionLit, UnionType,
+    };
+
+    // Small helper enum to avoid repetition
+    enum Ret<'a> {
+        RetValue(Value),
+        RetThunk(Thunk),
+        RetThunkRef(&'a Thunk),
+        RetExpr(ExprF<Thunk, Label, X>),
+    }
+    use Ret::{RetExpr, RetThunk, RetThunkRef, RetValue};
+
+    let ret = match expr {
+        ExprF::Embed(_) => unreachable!(),
+        ExprF::Var(_) => unreachable!(),
+        ExprF::Annot(x, _) => RetThunk(x),
+        ExprF::Lam(x, t, e) => RetValue(Lam(x.into(), t, e)),
+        ExprF::Pi(x, t, e) => RetValue(Pi(
+            x.into(),
+            TypeThunk::from_thunk(t),
+            TypeThunk::from_thunk(e),
+        )),
+        ExprF::Let(x, _, v, b) => {
+            let v = Typed::from_thunk_untyped(v);
+            RetThunk(b.subst_shift(&x.into(), &v))
+        }
+        ExprF::App(v, a) => RetValue(v.app_thunk(a)),
+        ExprF::Builtin(b) => RetValue(Value::from_builtin(b)),
+        ExprF::Const(c) => RetValue(Value::Const(c)),
+        ExprF::BoolLit(b) => RetValue(BoolLit(b)),
+        ExprF::NaturalLit(n) => RetValue(NaturalLit(n)),
+        ExprF::IntegerLit(n) => RetValue(IntegerLit(n)),
+        ExprF::DoubleLit(_) => RetExpr(expr),
+        ExprF::OldOptionalLit(None, t) => {
+            RetValue(EmptyOptionalLit(TypeThunk::from_thunk(t)))
+        }
+        ExprF::OldOptionalLit(Some(e), _) => RetValue(NEOptionalLit(e)),
+        ExprF::SomeLit(e) => RetValue(NEOptionalLit(e)),
+        ExprF::EmptyListLit(t) => {
+            RetValue(EmptyListLit(TypeThunk::from_thunk(t)))
+        }
+        ExprF::NEListLit(elts) => {
+            RetValue(NEListLit(elts.into_iter().collect()))
+        }
+        ExprF::RecordLit(kvs) => RetValue(RecordLit(kvs.into_iter().collect())),
+        ExprF::RecordType(kts) => RetValue(RecordType(
+            kts.into_iter()
+                .map(|(k, t)| (k, TypeThunk::from_thunk(t)))
+                .collect(),
+        )),
+        ExprF::UnionLit(l, x, kts) => RetValue(UnionLit(
+            l,
+            x,
+            kts.into_iter()
+                .map(|(k, t)| (k, t.map(|t| TypeThunk::from_thunk(t))))
+                .collect(),
+        )),
+        ExprF::UnionType(kts) => RetValue(UnionType(
+            kts.into_iter()
+                .map(|(k, t)| (k, t.map(|t| TypeThunk::from_thunk(t))))
+                .collect(),
+        )),
+        ExprF::TextLit(elts) => {
+            use InterpolatedTextContents::Expr;
+            let elts: Vec<_> = squash_textlit(elts.into_iter());
+            // Simplify bare interpolation
+            if let [Expr(th)] = elts.as_slice() {
+                RetThunk(th.clone())
+            } else {
+                RetValue(TextLit(elts))
+            }
+        }
+        ExprF::BoolIf(ref b, ref e1, ref e2) => {
+            let b_borrow = b.as_value();
+            match &*b_borrow {
+                BoolLit(true) => RetThunkRef(e1),
+                BoolLit(false) => RetThunkRef(e2),
+                _ => {
+                    let e1_borrow = e1.as_value();
+                    let e2_borrow = e2.as_value();
+                    match (&*e1_borrow, &*e2_borrow) {
+                        // Simplify `if b then True else False`
+                        (BoolLit(true), BoolLit(false)) => RetThunkRef(b),
+                        _ if e1 == e2 => RetThunkRef(e1),
+                        _ => {
+                            drop(b_borrow);
+                            drop(e1_borrow);
+                            drop(e2_borrow);
+                            RetExpr(expr)
+                        }
+                    }
+                }
+            }
+        }
+        ExprF::BinOp(o, ref x, ref y) => {
+            use BinOp::{
+                BoolAnd, BoolEQ, BoolNE, BoolOr, ListAppend, NaturalPlus,
+                NaturalTimes, TextAppend,
+            };
+            let x_borrow = x.as_value();
+            let y_borrow = y.as_value();
+            match (o, &*x_borrow, &*y_borrow) {
+                (BoolAnd, BoolLit(true), _) => RetThunkRef(y),
+                (BoolAnd, _, BoolLit(true)) => RetThunkRef(x),
+                (BoolAnd, BoolLit(false), _) => RetValue(BoolLit(false)),
+                (BoolAnd, _, BoolLit(false)) => RetValue(BoolLit(false)),
+                (BoolAnd, _, _) if x == y => RetThunkRef(x),
+                (BoolOr, BoolLit(true), _) => RetValue(BoolLit(true)),
+                (BoolOr, _, BoolLit(true)) => RetValue(BoolLit(true)),
+                (BoolOr, BoolLit(false), _) => RetThunkRef(y),
+                (BoolOr, _, BoolLit(false)) => RetThunkRef(x),
+                (BoolOr, _, _) if x == y => RetThunkRef(x),
+                (BoolEQ, BoolLit(true), _) => RetThunkRef(y),
+                (BoolEQ, _, BoolLit(true)) => RetThunkRef(x),
+                (BoolEQ, BoolLit(x), BoolLit(y)) => RetValue(BoolLit(x == y)),
+                (BoolEQ, _, _) if x == y => RetValue(BoolLit(true)),
+                (BoolNE, BoolLit(false), _) => RetThunkRef(y),
+                (BoolNE, _, BoolLit(false)) => RetThunkRef(x),
+                (BoolNE, BoolLit(x), BoolLit(y)) => RetValue(BoolLit(x != y)),
+                (BoolNE, _, _) if x == y => RetValue(BoolLit(false)),
+
+                (NaturalPlus, NaturalLit(0), _) => RetThunkRef(y),
+                (NaturalPlus, _, NaturalLit(0)) => RetThunkRef(x),
+                (NaturalPlus, NaturalLit(x), NaturalLit(y)) => {
+                    RetValue(NaturalLit(x + y))
+                }
+                (NaturalTimes, NaturalLit(0), _) => RetValue(NaturalLit(0)),
+                (NaturalTimes, _, NaturalLit(0)) => RetValue(NaturalLit(0)),
+                (NaturalTimes, NaturalLit(1), _) => RetThunkRef(y),
+                (NaturalTimes, _, NaturalLit(1)) => RetThunkRef(x),
+                (NaturalTimes, NaturalLit(x), NaturalLit(y)) => {
+                    RetValue(NaturalLit(x * y))
+                }
+
+                (ListAppend, EmptyListLit(_), _) => RetThunkRef(y),
+                (ListAppend, _, EmptyListLit(_)) => RetThunkRef(x),
+                (ListAppend, NEListLit(xs), NEListLit(ys)) => RetValue(
+                    NEListLit(xs.iter().chain(ys.iter()).cloned().collect()),
+                ),
+
+                (TextAppend, TextLit(x), _) if x.is_empty() => RetThunkRef(y),
+                (TextAppend, _, TextLit(y)) if y.is_empty() => RetThunkRef(x),
+                (TextAppend, TextLit(x), TextLit(y)) => RetValue(TextLit(
+                    squash_textlit(x.iter().chain(y.iter()).cloned()),
+                )),
+                (TextAppend, TextLit(x), _) => {
+                    use std::iter::once;
+                    let y = InterpolatedTextContents::Expr(y.clone());
+                    RetValue(TextLit(squash_textlit(
+                        x.iter().cloned().chain(once(y)),
+                    )))
+                }
+                (TextAppend, _, TextLit(y)) => {
+                    use std::iter::once;
+                    let x = InterpolatedTextContents::Expr(x.clone());
+                    RetValue(TextLit(squash_textlit(
+                        once(x).chain(y.iter().cloned()),
+                    )))
+                }
+
+                _ => {
+                    drop(x_borrow);
+                    drop(y_borrow);
+                    RetExpr(expr)
+                }
+            }
+        }
+
+        ExprF::Projection(_, ls) if ls.is_empty() => {
+            RetValue(RecordLit(std::collections::BTreeMap::new()))
+        }
+        ExprF::Projection(ref v, ref ls) => {
+            let v_borrow = v.as_value();
+            match &*v_borrow {
+                RecordLit(kvs) => RetValue(RecordLit(
+                    ls.iter()
+                        .filter_map(|l| {
+                            kvs.get(l).map(|x| (l.clone(), x.clone()))
+                        })
+                        .collect(),
+                )),
+                _ => {
+                    drop(v_borrow);
+                    RetExpr(expr)
+                }
+            }
+        }
+        ExprF::Field(ref v, ref l) => {
+            let v_borrow = v.as_value();
+            match &*v_borrow {
+                RecordLit(kvs) => match kvs.get(l) {
+                    Some(r) => RetThunk(r.clone()),
+                    None => {
+                        drop(v_borrow);
+                        RetExpr(expr)
+                    }
+                },
+                UnionType(kts) => {
+                    RetValue(UnionConstructor(l.clone(), kts.clone()))
+                }
+                _ => {
+                    drop(v_borrow);
+                    RetExpr(expr)
+                }
+            }
+        }
+
+        ExprF::Merge(ref handlers, ref variant, _) => {
+            let handlers_borrow = handlers.as_value();
+            let variant_borrow = variant.as_value();
+            match (&*handlers_borrow, &*variant_borrow) {
+                (RecordLit(kvs), UnionConstructor(l, _)) => match kvs.get(l) {
+                    Some(h) => RetThunk(h.clone()),
+                    None => {
+                        drop(handlers_borrow);
+                        drop(variant_borrow);
+                        RetExpr(expr)
+                    }
+                },
+                (RecordLit(kvs), UnionLit(l, v, _)) => match kvs.get(l) {
+                    Some(h) => RetValue(h.app_thunk(v.clone())),
+                    None => {
+                        drop(handlers_borrow);
+                        drop(variant_borrow);
+                        RetExpr(expr)
+                    }
+                },
+                _ => {
+                    drop(handlers_borrow);
+                    drop(variant_borrow);
+                    RetExpr(expr)
+                }
+            }
+        }
+    };
+
+    match ret {
+        RetValue(v) => v,
+        RetThunk(th) => th.to_value(),
+        RetThunkRef(th) => th.to_value(),
+        RetExpr(expr) => Value::PartialExpr(expr),
+    }
+}
+
+#[cfg(test)]
+mod spec_tests {
+    #![rustfmt::skip]
+
+    macro_rules! norm {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(Normalization, Success, $name, $path);
+        };
+    }
+
+    macro_rules! alpha_norm {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(AlphaNormalization, Success, $name, $path);
+        };
+    }
+
+    norm!(success_haskell_tutorial_access_0, "haskell-tutorial/access/0");
+    norm!(success_haskell_tutorial_access_1, "haskell-tutorial/access/1");
+    // norm!(success_haskell_tutorial_combineTypes_0, "haskell-tutorial/combineTypes/0");
+    // norm!(success_haskell_tutorial_combineTypes_1, "haskell-tutorial/combineTypes/1");
+    // norm!(success_haskell_tutorial_prefer_0, "haskell-tutorial/prefer/0");
+    norm!(success_haskell_tutorial_projection_0, "haskell-tutorial/projection/0");
+
+    norm!(success_prelude_Bool_and_0, "prelude/Bool/and/0");
+    norm!(success_prelude_Bool_and_1, "prelude/Bool/and/1");
+    norm!(success_prelude_Bool_build_0, "prelude/Bool/build/0");
+    norm!(success_prelude_Bool_build_1, "prelude/Bool/build/1");
+    norm!(success_prelude_Bool_even_0, "prelude/Bool/even/0");
+    norm!(success_prelude_Bool_even_1, "prelude/Bool/even/1");
+    norm!(success_prelude_Bool_even_2, "prelude/Bool/even/2");
+    norm!(success_prelude_Bool_even_3, "prelude/Bool/even/3");
+    norm!(success_prelude_Bool_fold_0, "prelude/Bool/fold/0");
+    norm!(success_prelude_Bool_fold_1, "prelude/Bool/fold/1");
+    norm!(success_prelude_Bool_not_0, "prelude/Bool/not/0");
+    norm!(success_prelude_Bool_not_1, "prelude/Bool/not/1");
+    norm!(success_prelude_Bool_odd_0, "prelude/Bool/odd/0");
+    norm!(success_prelude_Bool_odd_1, "prelude/Bool/odd/1");
+    norm!(success_prelude_Bool_odd_2, "prelude/Bool/odd/2");
+    norm!(success_prelude_Bool_odd_3, "prelude/Bool/odd/3");
+    norm!(success_prelude_Bool_or_0, "prelude/Bool/or/0");
+    norm!(success_prelude_Bool_or_1, "prelude/Bool/or/1");
+    norm!(success_prelude_Bool_show_0, "prelude/Bool/show/0");
+    norm!(success_prelude_Bool_show_1, "prelude/Bool/show/1");
+    // norm!(success_prelude_Double_show_0, "prelude/Double/show/0");
+    // norm!(success_prelude_Double_show_1, "prelude/Double/show/1");
+    // norm!(success_prelude_Integer_show_0, "prelude/Integer/show/0");
+    // norm!(success_prelude_Integer_show_1, "prelude/Integer/show/1");
+    // norm!(success_prelude_Integer_toDouble_0, "prelude/Integer/toDouble/0");
+    // norm!(success_prelude_Integer_toDouble_1, "prelude/Integer/toDouble/1");
+    norm!(success_prelude_List_all_0, "prelude/List/all/0");
+    norm!(success_prelude_List_all_1, "prelude/List/all/1");
+    norm!(success_prelude_List_any_0, "prelude/List/any/0");
+    norm!(success_prelude_List_any_1, "prelude/List/any/1");
+    norm!(success_prelude_List_build_0, "prelude/List/build/0");
+    norm!(success_prelude_List_build_1, "prelude/List/build/1");
+    norm!(success_prelude_List_concat_0, "prelude/List/concat/0");
+    norm!(success_prelude_List_concat_1, "prelude/List/concat/1");
+    norm!(success_prelude_List_concatMap_0, "prelude/List/concatMap/0");
+    norm!(success_prelude_List_concatMap_1, "prelude/List/concatMap/1");
+    norm!(success_prelude_List_filter_0, "prelude/List/filter/0");
+    norm!(success_prelude_List_filter_1, "prelude/List/filter/1");
+    norm!(success_prelude_List_fold_0, "prelude/List/fold/0");
+    norm!(success_prelude_List_fold_1, "prelude/List/fold/1");
+    norm!(success_prelude_List_fold_2, "prelude/List/fold/2");
+    norm!(success_prelude_List_generate_0, "prelude/List/generate/0");
+    norm!(success_prelude_List_generate_1, "prelude/List/generate/1");
+    norm!(success_prelude_List_head_0, "prelude/List/head/0");
+    norm!(success_prelude_List_head_1, "prelude/List/head/1");
+    norm!(success_prelude_List_indexed_0, "prelude/List/indexed/0");
+    norm!(success_prelude_List_indexed_1, "prelude/List/indexed/1");
+    norm!(success_prelude_List_iterate_0, "prelude/List/iterate/0");
+    norm!(success_prelude_List_iterate_1, "prelude/List/iterate/1");
+    norm!(success_prelude_List_last_0, "prelude/List/last/0");
+    norm!(success_prelude_List_last_1, "prelude/List/last/1");
+    norm!(success_prelude_List_length_0, "prelude/List/length/0");
+    norm!(success_prelude_List_length_1, "prelude/List/length/1");
+    norm!(success_prelude_List_map_0, "prelude/List/map/0");
+    norm!(success_prelude_List_map_1, "prelude/List/map/1");
+    norm!(success_prelude_List_null_0, "prelude/List/null/0");
+    norm!(success_prelude_List_null_1, "prelude/List/null/1");
+    norm!(success_prelude_List_replicate_0, "prelude/List/replicate/0");
+    norm!(success_prelude_List_replicate_1, "prelude/List/replicate/1");
+    norm!(success_prelude_List_reverse_0, "prelude/List/reverse/0");
+    norm!(success_prelude_List_reverse_1, "prelude/List/reverse/1");
+    norm!(success_prelude_List_shifted_0, "prelude/List/shifted/0");
+    norm!(success_prelude_List_shifted_1, "prelude/List/shifted/1");
+    norm!(success_prelude_List_unzip_0, "prelude/List/unzip/0");
+    norm!(success_prelude_List_unzip_1, "prelude/List/unzip/1");
+    norm!(success_prelude_Natural_build_0, "prelude/Natural/build/0");
+    norm!(success_prelude_Natural_build_1, "prelude/Natural/build/1");
+    norm!(success_prelude_Natural_enumerate_0, "prelude/Natural/enumerate/0");
+    norm!(success_prelude_Natural_enumerate_1, "prelude/Natural/enumerate/1");
+    norm!(success_prelude_Natural_even_0, "prelude/Natural/even/0");
+    norm!(success_prelude_Natural_even_1, "prelude/Natural/even/1");
+    norm!(success_prelude_Natural_fold_0, "prelude/Natural/fold/0");
+    norm!(success_prelude_Natural_fold_1, "prelude/Natural/fold/1");
+    norm!(success_prelude_Natural_fold_2, "prelude/Natural/fold/2");
+    norm!(success_prelude_Natural_isZero_0, "prelude/Natural/isZero/0");
+    norm!(success_prelude_Natural_isZero_1, "prelude/Natural/isZero/1");
+    norm!(success_prelude_Natural_odd_0, "prelude/Natural/odd/0");
+    norm!(success_prelude_Natural_odd_1, "prelude/Natural/odd/1");
+    norm!(success_prelude_Natural_product_0, "prelude/Natural/product/0");
+    norm!(success_prelude_Natural_product_1, "prelude/Natural/product/1");
+    norm!(success_prelude_Natural_show_0, "prelude/Natural/show/0");
+    norm!(success_prelude_Natural_show_1, "prelude/Natural/show/1");
+    norm!(success_prelude_Natural_sum_0, "prelude/Natural/sum/0");
+    norm!(success_prelude_Natural_sum_1, "prelude/Natural/sum/1");
+    // norm!(success_prelude_Natural_toDouble_0, "prelude/Natural/toDouble/0");
+    // norm!(success_prelude_Natural_toDouble_1, "prelude/Natural/toDouble/1");
+    norm!(success_prelude_Natural_toInteger_0, "prelude/Natural/toInteger/0");
+    norm!(success_prelude_Natural_toInteger_1, "prelude/Natural/toInteger/1");
+    norm!(success_prelude_Optional_all_0, "prelude/Optional/all/0");
+    norm!(success_prelude_Optional_all_1, "prelude/Optional/all/1");
+    norm!(success_prelude_Optional_any_0, "prelude/Optional/any/0");
+    norm!(success_prelude_Optional_any_1, "prelude/Optional/any/1");
+    norm!(success_prelude_Optional_build_0, "prelude/Optional/build/0");
+    norm!(success_prelude_Optional_build_1, "prelude/Optional/build/1");
+    norm!(success_prelude_Optional_concat_0, "prelude/Optional/concat/0");
+    norm!(success_prelude_Optional_concat_1, "prelude/Optional/concat/1");
+    norm!(success_prelude_Optional_concat_2, "prelude/Optional/concat/2");
+    norm!(success_prelude_Optional_filter_0, "prelude/Optional/filter/0");
+    norm!(success_prelude_Optional_filter_1, "prelude/Optional/filter/1");
+    norm!(success_prelude_Optional_fold_0, "prelude/Optional/fold/0");
+    norm!(success_prelude_Optional_fold_1, "prelude/Optional/fold/1");
+    norm!(success_prelude_Optional_head_0, "prelude/Optional/head/0");
+    norm!(success_prelude_Optional_head_1, "prelude/Optional/head/1");
+    norm!(success_prelude_Optional_head_2, "prelude/Optional/head/2");
+    norm!(success_prelude_Optional_last_0, "prelude/Optional/last/0");
+    norm!(success_prelude_Optional_last_1, "prelude/Optional/last/1");
+    norm!(success_prelude_Optional_last_2, "prelude/Optional/last/2");
+    norm!(success_prelude_Optional_length_0, "prelude/Optional/length/0");
+    norm!(success_prelude_Optional_length_1, "prelude/Optional/length/1");
+    norm!(success_prelude_Optional_map_0, "prelude/Optional/map/0");
+    norm!(success_prelude_Optional_map_1, "prelude/Optional/map/1");
+    norm!(success_prelude_Optional_null_0, "prelude/Optional/null/0");
+    norm!(success_prelude_Optional_null_1, "prelude/Optional/null/1");
+    norm!(success_prelude_Optional_toList_0, "prelude/Optional/toList/0");
+    norm!(success_prelude_Optional_toList_1, "prelude/Optional/toList/1");
+    norm!(success_prelude_Optional_unzip_0, "prelude/Optional/unzip/0");
+    norm!(success_prelude_Optional_unzip_1, "prelude/Optional/unzip/1");
+    norm!(success_prelude_Text_concat_0, "prelude/Text/concat/0");
+    norm!(success_prelude_Text_concat_1, "prelude/Text/concat/1");
+    norm!(success_prelude_Text_concatMap_0, "prelude/Text/concatMap/0");
+    norm!(success_prelude_Text_concatMap_1, "prelude/Text/concatMap/1");
+    // norm!(success_prelude_Text_concatMapSep_0, "prelude/Text/concatMapSep/0");
+    // norm!(success_prelude_Text_concatMapSep_1, "prelude/Text/concatMapSep/1");
+    // norm!(success_prelude_Text_concatSep_0, "prelude/Text/concatSep/0");
+    // norm!(success_prelude_Text_concatSep_1, "prelude/Text/concatSep/1");
+    // norm!(success_prelude_Text_show_0, "prelude/Text/show/0");
+    // norm!(success_prelude_Text_show_1, "prelude/Text/show/1");
+    // norm!(success_remoteSystems, "remoteSystems");
+
+    // norm!(success_simple_doubleShow, "simple/doubleShow");
+    norm!(success_simple_enum, "simple/enum");
+    // norm!(success_simple_integerShow, "simple/integerShow");
+    // norm!(success_simple_integerToDouble, "simple/integerToDouble");
+    norm!(success_simple_letlet, "simple/letlet");
+    norm!(success_simple_listBuild, "simple/listBuild");
+    norm!(success_simple_multiLine, "simple/multiLine");
+    norm!(success_simple_naturalBuild, "simple/naturalBuild");
+    norm!(success_simple_naturalPlus, "simple/naturalPlus");
+    norm!(success_simple_naturalShow, "simple/naturalShow");
+    norm!(success_simple_naturalToInteger, "simple/naturalToInteger");
+    norm!(success_simple_optionalBuild, "simple/optionalBuild");
+    norm!(success_simple_optionalBuildFold, "simple/optionalBuildFold");
+    norm!(success_simple_optionalFold, "simple/optionalFold");
+    // norm!(success_simple_sortOperator, "simple/sortOperator");
+    norm!(success_simplifications_and, "simplifications/and");
+    norm!(success_simplifications_eq, "simplifications/eq");
+    norm!(success_simplifications_ifThenElse, "simplifications/ifThenElse");
+    norm!(success_simplifications_ne, "simplifications/ne");
+    norm!(success_simplifications_or, "simplifications/or");
+
+    norm!(success_unit_Bool, "unit/Bool");
+    norm!(success_unit_Double, "unit/Double");
+    norm!(success_unit_DoubleLiteral, "unit/DoubleLiteral");
+    norm!(success_unit_DoubleShow, "unit/DoubleShow");
+    // norm!(success_unit_DoubleShowValue, "unit/DoubleShowValue");
+    norm!(success_unit_EmptyAlternative, "unit/EmptyAlternative");
+    norm!(success_unit_FunctionApplicationCapture, "unit/FunctionApplicationCapture");
+    norm!(success_unit_FunctionApplicationNoSubstitute, "unit/FunctionApplicationNoSubstitute");
+    norm!(success_unit_FunctionApplicationNormalizeArguments, "unit/FunctionApplicationNormalizeArguments");
+    norm!(success_unit_FunctionApplicationSubstitute, "unit/FunctionApplicationSubstitute");
+    norm!(success_unit_FunctionNormalizeArguments, "unit/FunctionNormalizeArguments");
+    norm!(success_unit_FunctionTypeNormalizeArguments, "unit/FunctionTypeNormalizeArguments");
+    norm!(success_unit_IfAlternativesIdentical, "unit/IfAlternativesIdentical");
+    norm!(success_unit_IfFalse, "unit/IfFalse");
+    norm!(success_unit_IfNormalizePredicateAndBranches, "unit/IfNormalizePredicateAndBranches");
+    norm!(success_unit_IfTrivial, "unit/IfTrivial");
+    norm!(success_unit_IfTrue, "unit/IfTrue");
+    norm!(success_unit_Integer, "unit/Integer");
+    norm!(success_unit_IntegerNegative, "unit/IntegerNegative");
+    norm!(success_unit_IntegerPositive, "unit/IntegerPositive");
+    // norm!(success_unit_IntegerShow_12, "unit/IntegerShow-12");
+    // norm!(success_unit_IntegerShow12, "unit/IntegerShow12");
+    norm!(success_unit_IntegerShow, "unit/IntegerShow");
+    // norm!(success_unit_IntegerToDouble_12, "unit/IntegerToDouble-12");
+    // norm!(success_unit_IntegerToDouble12, "unit/IntegerToDouble12");
+    norm!(success_unit_IntegerToDouble, "unit/IntegerToDouble");
+    norm!(success_unit_Kind, "unit/Kind");
+    norm!(success_unit_Let, "unit/Let");
+    norm!(success_unit_LetWithType, "unit/LetWithType");
+    norm!(success_unit_List, "unit/List");
+    norm!(success_unit_ListBuild, "unit/ListBuild");
+    norm!(success_unit_ListBuildFoldFusion, "unit/ListBuildFoldFusion");
+    norm!(success_unit_ListBuildImplementation, "unit/ListBuildImplementation");
+    norm!(success_unit_ListFold, "unit/ListFold");
+    norm!(success_unit_ListFoldEmpty, "unit/ListFoldEmpty");
+    norm!(success_unit_ListFoldOne, "unit/ListFoldOne");
+    norm!(success_unit_ListHead, "unit/ListHead");
+    norm!(success_unit_ListHeadEmpty, "unit/ListHeadEmpty");
+    norm!(success_unit_ListHeadOne, "unit/ListHeadOne");
+    norm!(success_unit_ListIndexed, "unit/ListIndexed");
+    norm!(success_unit_ListIndexedEmpty, "unit/ListIndexedEmpty");
+    norm!(success_unit_ListIndexedOne, "unit/ListIndexedOne");
+    norm!(success_unit_ListLast, "unit/ListLast");
+    norm!(success_unit_ListLastEmpty, "unit/ListLastEmpty");
+    norm!(success_unit_ListLastOne, "unit/ListLastOne");
+    norm!(success_unit_ListLength, "unit/ListLength");
+    norm!(success_unit_ListLengthEmpty, "unit/ListLengthEmpty");
+    norm!(success_unit_ListLengthOne, "unit/ListLengthOne");
+    norm!(success_unit_ListNormalizeElements, "unit/ListNormalizeElements");
+    norm!(success_unit_ListNormalizeTypeAnnotation, "unit/ListNormalizeTypeAnnotation");
+    norm!(success_unit_ListReverse, "unit/ListReverse");
+    norm!(success_unit_ListReverseEmpty, "unit/ListReverseEmpty");
+    norm!(success_unit_ListReverseTwo, "unit/ListReverseTwo");
+    norm!(success_unit_Merge, "unit/Merge");
+    norm!(success_unit_MergeEmptyAlternative, "unit/MergeEmptyAlternative");
+    norm!(success_unit_MergeNormalizeArguments, "unit/MergeNormalizeArguments");
+    norm!(success_unit_MergeWithType, "unit/MergeWithType");
+    norm!(success_unit_MergeWithTypeNormalizeArguments, "unit/MergeWithTypeNormalizeArguments");
+    norm!(success_unit_Natural, "unit/Natural");
+    norm!(success_unit_NaturalBuild, "unit/NaturalBuild");
+    norm!(success_unit_NaturalBuildFoldFusion, "unit/NaturalBuildFoldFusion");
+    norm!(success_unit_NaturalBuildImplementation, "unit/NaturalBuildImplementation");
+    norm!(success_unit_NaturalEven, "unit/NaturalEven");
+    norm!(success_unit_NaturalEvenOne, "unit/NaturalEvenOne");
+    norm!(success_unit_NaturalEvenZero, "unit/NaturalEvenZero");
+    norm!(success_unit_NaturalFold, "unit/NaturalFold");
+    norm!(success_unit_NaturalFoldOne, "unit/NaturalFoldOne");
+    norm!(success_unit_NaturalFoldZero, "unit/NaturalFoldZero");
+    norm!(success_unit_NaturalIsZero, "unit/NaturalIsZero");
+    norm!(success_unit_NaturalIsZeroOne, "unit/NaturalIsZeroOne");
+    norm!(success_unit_NaturalIsZeroZero, "unit/NaturalIsZeroZero");
+    norm!(success_unit_NaturalLiteral, "unit/NaturalLiteral");
+    norm!(success_unit_NaturalOdd, "unit/NaturalOdd");
+    norm!(success_unit_NaturalOddOne, "unit/NaturalOddOne");
+    norm!(success_unit_NaturalOddZero, "unit/NaturalOddZero");
+    norm!(success_unit_NaturalShow, "unit/NaturalShow");
+    norm!(success_unit_NaturalShowOne, "unit/NaturalShowOne");
+    norm!(success_unit_NaturalToInteger, "unit/NaturalToInteger");
+    norm!(success_unit_NaturalToIntegerOne, "unit/NaturalToIntegerOne");
+    norm!(success_unit_None, "unit/None");
+    norm!(success_unit_NoneNatural, "unit/NoneNatural");
+    norm!(success_unit_OperatorAndEquivalentArguments, "unit/OperatorAndEquivalentArguments");
+    norm!(success_unit_OperatorAndLhsFalse, "unit/OperatorAndLhsFalse");
+    norm!(success_unit_OperatorAndLhsTrue, "unit/OperatorAndLhsTrue");
+    norm!(success_unit_OperatorAndNormalizeArguments, "unit/OperatorAndNormalizeArguments");
+    norm!(success_unit_OperatorAndRhsFalse, "unit/OperatorAndRhsFalse");
+    norm!(success_unit_OperatorAndRhsTrue, "unit/OperatorAndRhsTrue");
+    norm!(success_unit_OperatorEqualEquivalentArguments, "unit/OperatorEqualEquivalentArguments");
+    norm!(success_unit_OperatorEqualLhsTrue, "unit/OperatorEqualLhsTrue");
+    norm!(success_unit_OperatorEqualNormalizeArguments, "unit/OperatorEqualNormalizeArguments");
+    norm!(success_unit_OperatorEqualRhsTrue, "unit/OperatorEqualRhsTrue");
+    norm!(success_unit_OperatorListConcatenateLhsEmpty, "unit/OperatorListConcatenateLhsEmpty");
+    norm!(success_unit_OperatorListConcatenateListList, "unit/OperatorListConcatenateListList");
+    norm!(success_unit_OperatorListConcatenateNormalizeArguments, "unit/OperatorListConcatenateNormalizeArguments");
+    norm!(success_unit_OperatorListConcatenateRhsEmpty, "unit/OperatorListConcatenateRhsEmpty");
+    norm!(success_unit_OperatorNotEqualEquivalentArguments, "unit/OperatorNotEqualEquivalentArguments");
+    norm!(success_unit_OperatorNotEqualLhsFalse, "unit/OperatorNotEqualLhsFalse");
+    norm!(success_unit_OperatorNotEqualNormalizeArguments, "unit/OperatorNotEqualNormalizeArguments");
+    norm!(success_unit_OperatorNotEqualRhsFalse, "unit/OperatorNotEqualRhsFalse");
+    norm!(success_unit_OperatorOrEquivalentArguments, "unit/OperatorOrEquivalentArguments");
+    norm!(success_unit_OperatorOrLhsFalse, "unit/OperatorOrLhsFalse");
+    norm!(success_unit_OperatorOrLhsTrue, "unit/OperatorOrLhsTrue");
+    norm!(success_unit_OperatorOrNormalizeArguments, "unit/OperatorOrNormalizeArguments");
+    norm!(success_unit_OperatorOrRhsFalse, "unit/OperatorOrRhsFalse");
+    norm!(success_unit_OperatorOrRhsTrue, "unit/OperatorOrRhsTrue");
+    norm!(success_unit_OperatorPlusLhsZero, "unit/OperatorPlusLhsZero");
+    norm!(success_unit_OperatorPlusNormalizeArguments, "unit/OperatorPlusNormalizeArguments");
+    norm!(success_unit_OperatorPlusOneAndOne, "unit/OperatorPlusOneAndOne");
+    norm!(success_unit_OperatorPlusRhsZero, "unit/OperatorPlusRhsZero");
+    norm!(success_unit_OperatorTextConcatenateLhsEmpty, "unit/OperatorTextConcatenateLhsEmpty");
+    norm!(success_unit_OperatorTextConcatenateLhsNonEmpty, "unit/OperatorTextConcatenateLhsNonEmpty");
+    norm!(success_unit_OperatorTextConcatenateTextText, "unit/OperatorTextConcatenateTextText");
+    norm!(success_unit_OperatorTimesLhsOne, "unit/OperatorTimesLhsOne");
+    norm!(success_unit_OperatorTimesLhsZero, "unit/OperatorTimesLhsZero");
+    norm!(success_unit_OperatorTimesNormalizeArguments, "unit/OperatorTimesNormalizeArguments");
+    norm!(success_unit_OperatorTimesRhsOne, "unit/OperatorTimesRhsOne");
+    norm!(success_unit_OperatorTimesRhsZero, "unit/OperatorTimesRhsZero");
+    norm!(success_unit_OperatorTimesTwoAndTwo, "unit/OperatorTimesTwoAndTwo");
+    norm!(success_unit_Optional, "unit/Optional");
+    norm!(success_unit_OptionalBuild, "unit/OptionalBuild");
+    norm!(success_unit_OptionalBuildFoldFusion, "unit/OptionalBuildFoldFusion");
+    norm!(success_unit_OptionalBuildImplementation, "unit/OptionalBuildImplementation");
+    norm!(success_unit_OptionalFold, "unit/OptionalFold");
+    norm!(success_unit_OptionalFoldNone, "unit/OptionalFoldNone");
+    norm!(success_unit_OptionalFoldSome, "unit/OptionalFoldSome");
+    norm!(success_unit_Record, "unit/Record");
+    norm!(success_unit_RecordEmpty, "unit/RecordEmpty");
+    norm!(success_unit_RecordProjection, "unit/RecordProjection");
+    norm!(success_unit_RecordProjectionEmpty, "unit/RecordProjectionEmpty");
+    norm!(success_unit_RecordProjectionNormalizeArguments, "unit/RecordProjectionNormalizeArguments");
+    norm!(success_unit_RecordSelection, "unit/RecordSelection");
+    norm!(success_unit_RecordSelectionNormalizeArguments, "unit/RecordSelectionNormalizeArguments");
+    norm!(success_unit_RecordType, "unit/RecordType");
+    norm!(success_unit_RecordTypeEmpty, "unit/RecordTypeEmpty");
+    // norm!(success_unit_RecursiveRecordMergeCollision, "unit/RecursiveRecordMergeCollision");
+    // norm!(success_unit_RecursiveRecordMergeLhsEmpty, "unit/RecursiveRecordMergeLhsEmpty");
+    // norm!(success_unit_RecursiveRecordMergeNoCollision, "unit/RecursiveRecordMergeNoCollision");
+    // norm!(success_unit_RecursiveRecordMergeNormalizeArguments, "unit/RecursiveRecordMergeNormalizeArguments");
+    // norm!(success_unit_RecursiveRecordMergeRhsEmpty, "unit/RecursiveRecordMergeRhsEmpty");
+    // norm!(success_unit_RecursiveRecordTypeMergeCollision, "unit/RecursiveRecordTypeMergeCollision");
+    // norm!(success_unit_RecursiveRecordTypeMergeLhsEmpty, "unit/RecursiveRecordTypeMergeLhsEmpty");
+    // norm!(success_unit_RecursiveRecordTypeMergeNoCollision, "unit/RecursiveRecordTypeMergeNoCollision");
+    // norm!(success_unit_RecursiveRecordTypeMergeNormalizeArguments, "unit/RecursiveRecordTypeMergeNormalizeArguments");
+    // norm!(success_unit_RecursiveRecordTypeMergeRhsEmpty, "unit/RecursiveRecordTypeMergeRhsEmpty");
+    // norm!(success_unit_RecursiveRecordTypeMergeSorts, "unit/RecursiveRecordTypeMergeSorts");
+    // norm!(success_unit_RightBiasedRecordMergeCollision, "unit/RightBiasedRecordMergeCollision");
+    // norm!(success_unit_RightBiasedRecordMergeLhsEmpty, "unit/RightBiasedRecordMergeLhsEmpty");
+    // norm!(success_unit_RightBiasedRecordMergeNoCollision, "unit/RightBiasedRecordMergeNoCollision");
+    // norm!(success_unit_RightBiasedRecordMergeNormalizeArguments, "unit/RightBiasedRecordMergeNormalizeArguments");
+    // norm!(success_unit_RightBiasedRecordMergeRhsEmpty, "unit/RightBiasedRecordMergeRhsEmpty");
+    norm!(success_unit_SomeNormalizeArguments, "unit/SomeNormalizeArguments");
+    norm!(success_unit_Sort, "unit/Sort");
+    norm!(success_unit_Text, "unit/Text");
+    norm!(success_unit_TextInterpolate, "unit/TextInterpolate");
+    norm!(success_unit_TextLiteral, "unit/TextLiteral");
+    norm!(success_unit_TextNormalizeInterpolations, "unit/TextNormalizeInterpolations");
+    norm!(success_unit_TextShow, "unit/TextShow");
+    // norm!(success_unit_TextShowAllEscapes, "unit/TextShowAllEscapes");
+    norm!(success_unit_True, "unit/True");
+    norm!(success_unit_Type, "unit/Type");
+    norm!(success_unit_TypeAnnotation, "unit/TypeAnnotation");
+    norm!(success_unit_UnionNormalizeAlternatives, "unit/UnionNormalizeAlternatives");
+    norm!(success_unit_UnionNormalizeArguments, "unit/UnionNormalizeArguments");
+    norm!(success_unit_UnionProjectConstructor, "unit/UnionProjectConstructor");
+    norm!(success_unit_UnionSortAlternatives, "unit/UnionSortAlternatives");
+    norm!(success_unit_UnionType, "unit/UnionType");
+    norm!(success_unit_UnionTypeEmpty, "unit/UnionTypeEmpty");
+    norm!(success_unit_UnionTypeNormalizeArguments, "unit/UnionTypeNormalizeArguments");
+    norm!(success_unit_Variable, "unit/Variable");
+
+    alpha_norm!(alpha_success_unit_FunctionBindingUnderscore, "unit/FunctionBindingUnderscore");
+    alpha_norm!(alpha_success_unit_FunctionBindingX, "unit/FunctionBindingX");
+    alpha_norm!(alpha_success_unit_FunctionNestedBindingX, "unit/FunctionNestedBindingX");
+    alpha_norm!(alpha_success_unit_FunctionTypeBindingUnderscore, "unit/FunctionTypeBindingUnderscore");
+    alpha_norm!(alpha_success_unit_FunctionTypeBindingX, "unit/FunctionTypeBindingX");
+    alpha_norm!(alpha_success_unit_FunctionTypeNestedBindingX, "unit/FunctionTypeNestedBindingX");
+}
diff --git a/dhall/src/phase/parse.rs b/dhall/src/phase/parse.rs
new file mode 100644
index 0000000..809faf4
--- /dev/null
+++ b/dhall/src/phase/parse.rs
@@ -0,0 +1,38 @@
+use std::fs::File;
+use std::io::Read;
+use std::path::Path;
+
+use dhall_syntax::parse_expr;
+
+use crate::error::Error;
+use crate::phase::resolve::ImportRoot;
+use crate::phase::Parsed;
+
+pub(crate) fn parse_file(f: &Path) -> Result<Parsed, Error> {
+    let mut buffer = String::new();
+    File::open(f)?.read_to_string(&mut buffer)?;
+    let expr = parse_expr(&*buffer)?;
+    let root = ImportRoot::LocalDir(f.parent().unwrap().to_owned());
+    Ok(Parsed(expr.unnote().note_absurd(), root))
+}
+
+pub(crate) fn parse_str(s: &str) -> Result<Parsed, Error> {
+    let expr = parse_expr(s)?;
+    let root = ImportRoot::LocalDir(std::env::current_dir()?);
+    Ok(Parsed(expr, root))
+}
+
+pub(crate) fn parse_binary_file(f: &Path) -> Result<Parsed, Error> {
+    let mut buffer = Vec::new();
+    File::open(f)?.read_to_end(&mut buffer)?;
+    let expr = crate::phase::binary::decode(&buffer)?;
+    let root = ImportRoot::LocalDir(f.parent().unwrap().to_owned());
+    Ok(Parsed(expr.note_absurd(), root))
+}
+
+#[cfg(test)]
+mod spec_tests {
+    #![rustfmt::skip]
+    // See build.rs
+    include!(concat!(env!("OUT_DIR"), "/parser_tests.rs"));
+}
diff --git a/dhall/src/phase/resolve.rs b/dhall/src/phase/resolve.rs
new file mode 100644
index 0000000..afb49cb
--- /dev/null
+++ b/dhall/src/phase/resolve.rs
@@ -0,0 +1,139 @@
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+
+use dhall_syntax::Import;
+
+use crate::error::Error;
+use crate::phase::{Normalized, Parsed, Resolved};
+
+#[derive(Debug)]
+pub enum ImportError {
+    Recursive(Import, Box<Error>),
+    UnexpectedImport(Import),
+    ImportCycle(ImportStack, Import),
+}
+
+/// A root from which to resolve relative imports.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ImportRoot {
+    LocalDir(PathBuf),
+}
+
+type ImportCache = HashMap<Import, Normalized>;
+
+type ImportStack = Vec<Import>;
+
+fn resolve_import(
+    import: &Import,
+    root: &ImportRoot,
+    import_cache: &mut ImportCache,
+    import_stack: &ImportStack,
+) -> Result<Normalized, ImportError> {
+    use self::ImportRoot::*;
+    use dhall_syntax::FilePrefix::*;
+    use dhall_syntax::ImportLocation::*;
+    let cwd = match root {
+        LocalDir(cwd) => cwd,
+    };
+    match &import.location_hashed.location {
+        Local(prefix, path) => {
+            let path = match prefix {
+                // TODO: fail gracefully
+                Parent => cwd.parent().unwrap().join(path),
+                Here => cwd.join(path),
+                _ => unimplemented!("{:?}", import),
+            };
+            Ok(load_import(&path, import_cache, import_stack).map_err(|e| {
+                ImportError::Recursive(import.clone(), Box::new(e))
+            })?)
+        }
+        _ => unimplemented!("{:?}", import),
+    }
+}
+
+fn load_import(
+    f: &Path,
+    import_cache: &mut ImportCache,
+    import_stack: &ImportStack,
+) -> Result<Normalized, Error> {
+    Ok(
+        do_resolve_expr(Parsed::parse_file(f)?, import_cache, import_stack)?
+            .typecheck()?
+            .normalize(),
+    )
+}
+
+fn do_resolve_expr(
+    Parsed(expr, root): Parsed,
+    import_cache: &mut ImportCache,
+    import_stack: &ImportStack,
+) -> Result<Resolved, ImportError> {
+    let resolve = |import: &Import| -> Result<Normalized, ImportError> {
+        if import_stack.contains(import) {
+            return Err(ImportError::ImportCycle(
+                import_stack.clone(),
+                import.clone(),
+            ));
+        }
+        match import_cache.get(import) {
+            Some(expr) => Ok(expr.clone()),
+            None => {
+                // Copy the import stack and push the current import
+                let mut import_stack = import_stack.clone();
+                import_stack.push(import.clone());
+
+                // Resolve the import recursively
+                let expr =
+                    resolve_import(import, &root, import_cache, &import_stack)?;
+
+                // Add the import to the cache
+                import_cache.insert(import.clone(), expr.clone());
+                Ok(expr)
+            }
+        }
+    };
+    let expr = expr.traverse_embed(resolve)?;
+    Ok(Resolved(expr))
+}
+
+pub(crate) fn resolve(e: Parsed) -> Result<Resolved, ImportError> {
+    do_resolve_expr(e, &mut HashMap::new(), &Vec::new())
+}
+
+pub(crate) fn skip_resolve_expr(
+    Parsed(expr, _root): Parsed,
+) -> Result<Resolved, ImportError> {
+    let resolve = |import: &Import| -> Result<Normalized, ImportError> {
+        Err(ImportError::UnexpectedImport(import.clone()))
+    };
+    let expr = expr.traverse_embed(resolve)?;
+    Ok(Resolved(expr))
+}
+
+#[cfg(test)]
+mod spec_tests {
+    #![rustfmt::skip]
+
+    macro_rules! import_success {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(Import, Success, $name, $path);
+        };
+    }
+
+    // macro_rules! import_failure {
+    //     ($name:ident, $path:expr) => {
+    //         make_spec_test!(Import, Failure, $name, $path);
+    //     };
+    // }
+
+    // import_success!(success_alternativeEnvNatural, "alternativeEnvNatural");
+    // import_success!(success_alternativeEnvSimple, "alternativeEnvSimple");
+    // import_success!(success_alternativeNatural, "alternativeNatural");
+    // import_success!(success_asText, "asText");
+    import_success!(success_fieldOrder, "fieldOrder");
+    // import_failure!(failure_alternativeEnv, "alternativeEnv");
+    // import_failure!(failure_alternativeEnvMissing, "alternativeEnvMissing");
+    // import_failure!(failure_cycle, "cycle");
+    // import_failure!(failure_missing, "missing");
+    // import_failure!(failure_referentiallyInsane, "referentiallyInsane");
+}
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
new file mode 100644
index 0000000..6b12077
--- /dev/null
+++ b/dhall/src/phase/typecheck.rs
@@ -0,0 +1,1276 @@
+#![allow(non_snake_case)]
+use std::borrow::Borrow;
+use std::borrow::Cow;
+use std::collections::BTreeMap;
+use std::fmt;
+
+use crate::phase::normalize::{
+    AlphaVar, NormalizationContext, Thunk, TypeThunk, Value,
+};
+use crate::phase::*;
+use crate::traits::DynamicType;
+use dhall_proc_macros as dhall;
+use dhall_syntax;
+use dhall_syntax::context::Context;
+use dhall_syntax::*;
+
+use self::TypeMessage::*;
+
+impl TypeThunk {
+    fn to_type(&self, ctx: &TypecheckContext) -> Result<Type, TypeError> {
+        match self {
+            TypeThunk::Type(t) => Ok(t.clone()),
+            TypeThunk::Thunk(th) => {
+                // TODO: rule out statically
+                mktype(ctx, th.normalize_to_expr().embed_absurd().note_absurd())
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) enum EnvItem {
+    Type(AlphaVar, Type),
+    Value(Normalized),
+}
+
+impl EnvItem {
+    fn shift(&self, delta: isize, var: &AlphaVar) -> Self {
+        use EnvItem::*;
+        match self {
+            Type(v, e) => Type(v.shift(delta, var), e.shift(delta, var)),
+            Value(e) => Value(e.shift(delta, var)),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct TypecheckContext(pub(crate) Context<Label, EnvItem>);
+
+impl TypecheckContext {
+    pub(crate) fn new() -> Self {
+        TypecheckContext(Context::new())
+    }
+    pub(crate) fn insert_type(&self, x: &Label, t: Type) -> Self {
+        TypecheckContext(
+            self.0.map(|_, e| e.shift(1, &x.into())).insert(
+                x.clone(),
+                EnvItem::Type(x.into(), t.shift(1, &x.into())),
+            ),
+        )
+    }
+    pub(crate) fn insert_value(&self, x: &Label, t: Normalized) -> Self {
+        TypecheckContext(self.0.insert(x.clone(), EnvItem::Value(t)))
+    }
+    pub(crate) fn lookup(&self, var: &V<Label>) -> Option<Cow<'_, Type>> {
+        let V(x, n) = var;
+        match self.0.lookup(x, *n) {
+            Some(EnvItem::Type(_, t)) => Some(Cow::Borrowed(&t)),
+            Some(EnvItem::Value(t)) => Some(t.get_type()?),
+            None => None,
+        }
+    }
+    fn to_normalization_ctx(&self) -> NormalizationContext {
+        NormalizationContext::from_typecheck_ctx(self)
+    }
+}
+
+impl PartialEq for TypecheckContext {
+    fn eq(&self, _: &Self) -> bool {
+        // don't count contexts when comparing stuff
+        // this is dirty but needed for now
+        true
+    }
+}
+impl Eq for TypecheckContext {}
+
+fn function_check(a: Const, b: Const) -> Result<Const, ()> {
+    use dhall_syntax::Const::*;
+    match (a, b) {
+        (_, Type) => Ok(Type),
+        (Kind, Kind) => Ok(Kind),
+        (Sort, Sort) => Ok(Sort),
+        (Sort, Kind) => Ok(Sort),
+        _ => Err(()),
+    }
+}
+
+// Equality up to alpha-equivalence (renaming of bound variables)
+fn prop_equal<T, U>(eL0: T, eR0: U) -> bool
+where
+    T: Borrow<Type>,
+    U: Borrow<Type>,
+{
+    eL0.borrow().to_value() == eR0.borrow().to_value()
+}
+
+pub(crate) fn const_to_typed(c: Const) -> Typed {
+    match c {
+        Const::Sort => Typed::const_sort(),
+        _ => Typed::from_thunk_and_type(
+            Value::Const(c).into_thunk(),
+            type_of_const(c).unwrap(),
+        ),
+    }
+}
+
+fn const_to_type(c: Const) -> Type {
+    Type(TypeInternal::Const(c))
+}
+
+pub(crate) fn type_of_const(c: Const) -> Result<Type, TypeError> {
+    match c {
+        Const::Type => Ok(Type::const_kind()),
+        Const::Kind => Ok(Type::const_sort()),
+        Const::Sort => {
+            return Err(TypeError::new(
+                &TypecheckContext::new(),
+                TypeMessage::Sort,
+            ))
+        }
+    }
+}
+
+fn type_of_builtin<E>(b: Builtin) -> Expr<X, E> {
+    use dhall_syntax::Builtin::*;
+    match b {
+        Bool | Natural | Integer | Double | Text => dhall::expr!(Type),
+        List | Optional => dhall::expr!(
+            Type -> Type
+        ),
+
+        NaturalFold => dhall::expr!(
+            Natural ->
+            forall (natural: Type) ->
+            forall (succ: natural -> natural) ->
+            forall (zero: natural) ->
+            natural
+        ),
+        NaturalBuild => dhall::expr!(
+            (forall (natural: Type) ->
+                forall (succ: natural -> natural) ->
+                forall (zero: natural) ->
+                natural) ->
+            Natural
+        ),
+        NaturalIsZero | NaturalEven | NaturalOdd => dhall::expr!(
+            Natural -> Bool
+        ),
+        NaturalToInteger => dhall::expr!(Natural -> Integer),
+        NaturalShow => dhall::expr!(Natural -> Text),
+
+        IntegerToDouble => dhall::expr!(Integer -> Double),
+        IntegerShow => dhall::expr!(Integer -> Text),
+        DoubleShow => dhall::expr!(Double -> Text),
+        TextShow => dhall::expr!(Text -> Text),
+
+        ListBuild => dhall::expr!(
+            forall (a: Type) ->
+            (forall (list: Type) ->
+                forall (cons: a -> list -> list) ->
+                forall (nil: list) ->
+                list) ->
+            List a
+        ),
+        ListFold => dhall::expr!(
+            forall (a: Type) ->
+            List a ->
+            forall (list: Type) ->
+            forall (cons: a -> list -> list) ->
+            forall (nil: list) ->
+            list
+        ),
+        ListLength => dhall::expr!(forall (a: Type) -> List a -> Natural),
+        ListHead | ListLast => {
+            dhall::expr!(forall (a: Type) -> List a -> Optional a)
+        }
+        ListIndexed => dhall::expr!(
+            forall (a: Type) ->
+            List a ->
+            List { index: Natural, value: a }
+        ),
+        ListReverse => dhall::expr!(
+            forall (a: Type) -> List a -> List a
+        ),
+
+        OptionalBuild => dhall::expr!(
+            forall (a: Type) ->
+            (forall (optional: Type) ->
+                forall (just: a -> optional) ->
+                forall (nothing: optional) ->
+                optional) ->
+            Optional a
+        ),
+        OptionalFold => dhall::expr!(
+            forall (a: Type) ->
+            Optional a ->
+            forall (optional: Type) ->
+            forall (just: a -> optional) ->
+            forall (nothing: optional) ->
+            optional
+        ),
+        OptionalNone => dhall::expr!(
+            forall (a: Type) -> Optional a
+        ),
+    }
+}
+
+macro_rules! ensure_equal {
+    ($x:expr, $y:expr, $err:expr $(,)*) => {
+        if !prop_equal($x, $y) {
+            return Err($err);
+        }
+    };
+}
+
+// Ensure the provided type has type `Type`
+macro_rules! ensure_simple_type {
+    ($x:expr, $err:expr $(,)*) => {{
+        match $x.get_type()?.as_const() {
+            Some(dhall_syntax::Const::Type) => {}
+            _ => return Err($err),
+        }
+    }};
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) enum TypeIntermediate {
+    Pi(TypecheckContext, Label, Type, Type),
+    RecordType(TypecheckContext, BTreeMap<Label, Type>),
+    UnionType(TypecheckContext, BTreeMap<Label, Option<Type>>),
+    ListType(TypecheckContext, Type),
+    OptionalType(TypecheckContext, Type),
+}
+
+impl TypeIntermediate {
+    fn typecheck(self) -> Result<Typed, TypeError> {
+        let mkerr = |ctx, msg| TypeError::new(ctx, msg);
+        Ok(match &self {
+            TypeIntermediate::Pi(ctx, x, ta, tb) => {
+                let ctx2 = ctx.insert_type(x, ta.clone());
+
+                let kA = match ta.get_type()?.as_const() {
+                    Some(k) => k,
+                    _ => {
+                        return Err(mkerr(
+                            ctx,
+                            InvalidInputType(ta.clone().to_normalized()),
+                        ))
+                    }
+                };
+
+                let kB = match tb.get_type()?.as_const() {
+                    Some(k) => k,
+                    _ => {
+                        return Err(mkerr(
+                            &ctx2,
+                            InvalidOutputType(
+                                tb.clone()
+                                    .to_normalized()
+                                    .get_type()?
+                                    .to_normalized(),
+                            ),
+                        ))
+                    }
+                };
+
+                let k = match function_check(kA, kB) {
+                    Ok(k) => k,
+                    Err(()) => {
+                        return Err(mkerr(
+                            ctx,
+                            NoDependentTypes(
+                                ta.clone().to_normalized(),
+                                tb.clone()
+                                    .to_normalized()
+                                    .get_type()?
+                                    .to_normalized(),
+                            ),
+                        ))
+                    }
+                };
+
+                Typed::from_thunk_and_type(
+                    Value::Pi(
+                        x.clone().into(),
+                        TypeThunk::from_type(ta.clone()),
+                        TypeThunk::from_type(tb.clone()),
+                    )
+                    .into_thunk(),
+                    const_to_type(k),
+                )
+            }
+            TypeIntermediate::RecordType(ctx, kts) => {
+                // Check that all types are the same const
+                let mut k = None;
+                for (x, t) in kts {
+                    match (k, t.get_type()?.as_const()) {
+                        (None, Some(k2)) => k = Some(k2),
+                        (Some(k1), Some(k2)) if k1 == k2 => {}
+                        _ => {
+                            return Err(mkerr(
+                                ctx,
+                                InvalidFieldType(x.clone(), t.clone()),
+                            ))
+                        }
+                    }
+                }
+                // An empty record type has type Type
+                let k = k.unwrap_or(dhall_syntax::Const::Type);
+
+                Typed::from_thunk_and_type(
+                    Value::RecordType(
+                        kts.iter()
+                            .map(|(k, t)| {
+                                (k.clone(), TypeThunk::from_type(t.clone()))
+                            })
+                            .collect(),
+                    )
+                    .into_thunk(),
+                    const_to_type(k),
+                )
+            }
+            TypeIntermediate::UnionType(ctx, kts) => {
+                // Check that all types are the same const
+                let mut k = None;
+                for (x, t) in kts {
+                    if let Some(t) = t {
+                        match (k, t.get_type()?.as_const()) {
+                            (None, Some(k2)) => k = Some(k2),
+                            (Some(k1), Some(k2)) if k1 == k2 => {}
+                            _ => {
+                                return Err(mkerr(
+                                    ctx,
+                                    InvalidFieldType(x.clone(), t.clone()),
+                                ))
+                            }
+                        }
+                    }
+                }
+
+                // An empty union type has type Type;
+                // an union type with only unary variants also has type Type
+                let k = k.unwrap_or(dhall_syntax::Const::Type);
+
+                Typed::from_thunk_and_type(
+                    Value::UnionType(
+                        kts.iter()
+                            .map(|(k, t)| {
+                                (
+                                    k.clone(),
+                                    t.as_ref().map(|t| {
+                                        TypeThunk::from_type(t.clone())
+                                    }),
+                                )
+                            })
+                            .collect(),
+                    )
+                    .into_thunk(),
+                    const_to_type(k),
+                )
+            }
+            TypeIntermediate::ListType(ctx, t) => {
+                ensure_simple_type!(
+                    t,
+                    mkerr(ctx, InvalidListType(t.clone().to_normalized())),
+                );
+                Typed::from_thunk_and_type(
+                    Value::from_builtin(Builtin::List)
+                        .app(t.to_value())
+                        .into_thunk(),
+                    const_to_type(Const::Type),
+                )
+            }
+            TypeIntermediate::OptionalType(ctx, t) => {
+                ensure_simple_type!(
+                    t,
+                    mkerr(ctx, InvalidOptionalType(t.clone().to_normalized())),
+                );
+                Typed::from_thunk_and_type(
+                    Value::from_builtin(Builtin::Optional)
+                        .app(t.to_value())
+                        .into_thunk(),
+                    const_to_type(Const::Type),
+                )
+            }
+        })
+    }
+}
+
+/// Takes an expression that is meant to contain a Type
+/// and turn it into a type, typechecking it along the way.
+fn mktype(
+    ctx: &TypecheckContext,
+    e: SubExpr<Span, Normalized>,
+) -> Result<Type, TypeError> {
+    Ok(type_with(ctx, e)?.to_type())
+}
+
+fn builtin_to_type(b: Builtin) -> Result<Type, TypeError> {
+    mktype(
+        &TypecheckContext::new(),
+        SubExpr::from_expr_no_note(ExprF::Builtin(b)),
+    )
+}
+
+/// Intermediary return type
+enum Ret {
+    /// Returns the contained value as is
+    RetTyped(Typed),
+    /// Use the contained Type as the type of the input expression
+    RetType(Type),
+}
+
+/// Type-check an expression and return the expression alongside its type if type-checking
+/// succeeded, or an error if type-checking failed
+fn type_with(
+    ctx: &TypecheckContext,
+    e: SubExpr<Span, Normalized>,
+) -> Result<Typed, TypeError> {
+    use dhall_syntax::ExprF::{
+        Annot, App, Embed, Lam, Let, OldOptionalLit, Pi, SomeLit,
+    };
+
+    use Ret::*;
+    let ret = match e.as_ref() {
+        Lam(x, t, b) => {
+            let tx = mktype(ctx, t.clone())?;
+            let ctx2 = ctx.insert_type(x, tx.clone());
+            let b = type_with(&ctx2, b.clone())?;
+            let tb = b.get_type()?.into_owned();
+            Ok(RetType(
+                TypeIntermediate::Pi(ctx.clone(), x.clone(), tx, tb)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        Pi(x, ta, tb) => {
+            let ta = mktype(ctx, ta.clone())?;
+            let ctx2 = ctx.insert_type(x, ta.clone());
+            let tb = mktype(&ctx2, tb.clone())?;
+            Ok(RetTyped(
+                TypeIntermediate::Pi(ctx.clone(), x.clone(), ta, tb)
+                    .typecheck()?,
+            ))
+        }
+        Let(x, t, v, e) => {
+            let v = if let Some(t) = t {
+                t.rewrap(Annot(v.clone(), t.clone()))
+            } else {
+                v.clone()
+            };
+
+            let v = type_with(ctx, v)?.normalize();
+            let e = type_with(&ctx.insert_value(x, v.clone()), e.clone())?;
+
+            Ok(RetType(e.get_type()?.into_owned()))
+        }
+        OldOptionalLit(None, t) => {
+            let none = SubExpr::from_expr_no_note(ExprF::Builtin(
+                Builtin::OptionalNone,
+            ));
+            let e = e.rewrap(App(none, t.clone()));
+            return type_with(ctx, e);
+        }
+        OldOptionalLit(Some(x), t) => {
+            let optional =
+                SubExpr::from_expr_no_note(ExprF::Builtin(Builtin::Optional));
+            let x = x.rewrap(SomeLit(x.clone()));
+            let t = t.rewrap(App(optional, t.clone()));
+            let e = e.rewrap(Annot(x, t));
+            return type_with(ctx, e);
+        }
+        Embed(p) => Ok(RetTyped(p.clone().into())),
+        _ => type_last_layer(
+            ctx,
+            // Typecheck recursively all subexpressions
+            e.as_ref()
+                .traverse_ref_simple(|e| Ok(type_with(ctx, e.clone())?))?,
+        ),
+    }?;
+    Ok(match ret {
+        RetType(typ) => Typed::from_thunk_and_type(
+            Thunk::new(ctx.to_normalization_ctx(), e),
+            typ,
+        ),
+        RetTyped(tt) => tt,
+    })
+}
+
+/// When all sub-expressions have been typed, check the remaining toplevel
+/// layer.
+fn type_last_layer(
+    ctx: &TypecheckContext,
+    e: ExprF<Typed, Label, Normalized>,
+) -> Result<Ret, TypeError> {
+    use dhall_syntax::BinOp::*;
+    use dhall_syntax::Builtin::*;
+    use dhall_syntax::ExprF::*;
+    let mkerr = |msg: TypeMessage| TypeError::new(ctx, msg);
+
+    use Ret::*;
+    match e {
+        Lam(_, _, _) => unreachable!(),
+        Pi(_, _, _) => unreachable!(),
+        Let(_, _, _, _) => unreachable!(),
+        Embed(_) => unreachable!(),
+        Var(var) => match ctx.lookup(&var) {
+            Some(e) => Ok(RetType(e.into_owned())),
+            None => Err(mkerr(UnboundVariable(var.clone()))),
+        },
+        App(f, a) => {
+            let tf = f.get_type()?;
+            let tf_internal = tf.internal_whnf();
+            let (x, tx, tb) = match &tf_internal {
+                Some(Value::Pi(
+                    x,
+                    TypeThunk::Type(tx),
+                    TypeThunk::Type(tb),
+                )) => (x, tx, tb),
+                Some(Value::Pi(_, _, _)) => {
+                    panic!("ICE: this should not have happened")
+                }
+                _ => return Err(mkerr(NotAFunction(f.clone()))),
+            };
+            ensure_equal!(a.get_type()?, tx, {
+                mkerr(TypeMismatch(f.clone(), tx.clone().to_normalized(), a))
+            });
+
+            Ok(RetType(tb.subst_shift(&x.into(), &a)))
+        }
+        Annot(x, t) => {
+            let t = t.to_type();
+            ensure_equal!(
+                &t,
+                x.get_type()?,
+                mkerr(AnnotMismatch(x, t.to_normalized()))
+            );
+            Ok(RetType(x.get_type()?.into_owned()))
+        }
+        BoolIf(x, y, z) => {
+            ensure_equal!(
+                x.get_type()?,
+                &builtin_to_type(Bool)?,
+                mkerr(InvalidPredicate(x)),
+            );
+
+            ensure_simple_type!(
+                y.get_type()?,
+                mkerr(IfBranchMustBeTerm(true, y)),
+            );
+
+            ensure_simple_type!(
+                z.get_type()?,
+                mkerr(IfBranchMustBeTerm(false, z)),
+            );
+
+            ensure_equal!(
+                y.get_type()?,
+                z.get_type()?,
+                mkerr(IfBranchMismatch(y, z))
+            );
+
+            Ok(RetType(y.get_type()?.into_owned()))
+        }
+        EmptyListLit(t) => {
+            let t = t.to_type();
+            Ok(RetType(
+                TypeIntermediate::ListType(ctx.clone(), t)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        NEListLit(xs) => {
+            let mut iter = xs.into_iter().enumerate();
+            let (_, x) = iter.next().unwrap();
+            for (i, y) in iter {
+                ensure_equal!(
+                    x.get_type()?,
+                    y.get_type()?,
+                    mkerr(InvalidListElement(
+                        i,
+                        x.get_type()?.to_normalized(),
+                        y
+                    ))
+                );
+            }
+            let t = x.get_type()?.into_owned();
+            Ok(RetType(
+                TypeIntermediate::ListType(ctx.clone(), t)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        SomeLit(x) => {
+            let t = x.get_type()?.into_owned();
+            Ok(RetType(
+                TypeIntermediate::OptionalType(ctx.clone(), t)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        RecordType(kts) => {
+            let kts: BTreeMap<_, _> = kts
+                .into_iter()
+                .map(|(x, t)| Ok((x, t.to_type())))
+                .collect::<Result<_, _>>()?;
+            Ok(RetTyped(
+                TypeIntermediate::RecordType(ctx.clone(), kts).typecheck()?,
+            ))
+        }
+        UnionType(kts) => {
+            let kts: BTreeMap<_, _> = kts
+                .into_iter()
+                .map(|(x, t)| {
+                    Ok((
+                        x,
+                        match t {
+                            None => None,
+                            Some(t) => Some(t.to_type()),
+                        },
+                    ))
+                })
+                .collect::<Result<_, _>>()?;
+            Ok(RetTyped(
+                TypeIntermediate::UnionType(ctx.clone(), kts).typecheck()?,
+            ))
+        }
+        RecordLit(kvs) => {
+            let kts = kvs
+                .into_iter()
+                .map(|(x, v)| Ok((x, v.get_type()?.into_owned())))
+                .collect::<Result<_, _>>()?;
+            Ok(RetType(
+                TypeIntermediate::RecordType(ctx.clone(), kts)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        UnionLit(x, v, kvs) => {
+            let mut kts: std::collections::BTreeMap<_, _> = kvs
+                .into_iter()
+                .map(|(x, v)| {
+                    let t = match v {
+                        Some(x) => Some(x.to_type()),
+                        None => None,
+                    };
+                    Ok((x, t))
+                })
+                .collect::<Result<_, _>>()?;
+            let t = v.get_type()?.into_owned();
+            kts.insert(x, Some(t));
+            Ok(RetType(
+                TypeIntermediate::UnionType(ctx.clone(), kts)
+                    .typecheck()?
+                    .to_type(),
+            ))
+        }
+        Field(r, x) => {
+            match &r.get_type()?.internal_whnf() {
+                Some(Value::RecordType(kts)) => match kts.get(&x) {
+                    Some(tth) => {
+                        Ok(RetType(tth.to_type(ctx)?))
+                    },
+                    None => Err(mkerr(MissingRecordField(x, r.clone()))),
+                },
+                // TODO: branch here only when r.get_type() is a Const
+                _ => {
+                    let r = r.to_type();
+                    match &r.internal_whnf() {
+                        Some(Value::UnionType(kts)) => match kts.get(&x) {
+                            // Constructor has type T -> < x: T, ... >
+                            Some(Some(t)) => {
+                                Ok(RetType(
+                                    TypeIntermediate::Pi(
+                                        ctx.clone(),
+                                        "_".into(),
+                                        t.to_type(ctx)?,
+                                        r.clone(),
+                                    )
+                                    .typecheck()?
+                                    .to_type(),
+                                ))
+                            },
+                            Some(None) => {
+                                Ok(RetType(r.clone()))
+                            },
+                            None => {
+                                Err(mkerr(MissingUnionField(
+                                    x,
+                                    r.to_normalized(),
+                                )))
+                            },
+                        },
+                        _ => {
+                            Err(mkerr(NotARecord(
+                                x,
+                                r.to_normalized()
+                            )))
+                        },
+                    }
+                }
+                // _ => Err(mkerr(NotARecord(
+                //     x,
+                //     r.to_type()?.to_normalized(),
+                // ))),
+            }
+        }
+        Const(c) => Ok(RetTyped(const_to_typed(c))),
+        Builtin(b) => {
+            Ok(RetType(mktype(ctx, rc(type_of_builtin(b)).note_absurd())?))
+        }
+        BoolLit(_) => Ok(RetType(builtin_to_type(Bool)?)),
+        NaturalLit(_) => Ok(RetType(builtin_to_type(Natural)?)),
+        IntegerLit(_) => Ok(RetType(builtin_to_type(Integer)?)),
+        DoubleLit(_) => Ok(RetType(builtin_to_type(Double)?)),
+        TextLit(interpolated) => {
+            let text_type = builtin_to_type(Text)?;
+            for contents in interpolated.iter() {
+                use InterpolatedTextContents::Expr;
+                if let Expr(x) = contents {
+                    ensure_equal!(
+                        x.get_type()?,
+                        &text_type,
+                        mkerr(InvalidTextInterpolation(x)),
+                    );
+                }
+            }
+            Ok(RetType(text_type))
+        }
+        BinOp(o @ ListAppend, l, r) => {
+            match l.get_type()?.internal_whnf() {
+                Some(Value::AppliedBuiltin(List, _)) => {}
+                _ => return Err(mkerr(BinOpTypeMismatch(o, l.clone()))),
+            }
+
+            ensure_equal!(
+                l.get_type()?,
+                r.get_type()?,
+                mkerr(BinOpTypeMismatch(o, r))
+            );
+
+            Ok(RetType(l.get_type()?.into_owned()))
+        }
+        BinOp(o, l, r) => {
+            let t = builtin_to_type(match o {
+                BoolAnd => Bool,
+                BoolOr => Bool,
+                BoolEQ => Bool,
+                BoolNE => Bool,
+                NaturalPlus => Natural,
+                NaturalTimes => Natural,
+                TextAppend => Text,
+                ListAppend => unreachable!(),
+                _ => return Err(mkerr(Unimplemented)),
+            })?;
+
+            ensure_equal!(l.get_type()?, &t, mkerr(BinOpTypeMismatch(o, l)));
+
+            ensure_equal!(r.get_type()?, &t, mkerr(BinOpTypeMismatch(o, r)));
+
+            Ok(RetType(t))
+        }
+        _ => Err(mkerr(Unimplemented)),
+    }
+}
+
+/// `typeOf` is the same as `type_with` with an empty context, meaning that the
+/// expression must be closed (i.e. no free variables), otherwise type-checking
+/// will fail.
+fn type_of(e: SubExpr<Span, Normalized>) -> Result<Typed, TypeError> {
+    let ctx = TypecheckContext::new();
+    let e = type_with(&ctx, e)?;
+    // Ensure `e` has a type (i.e. `e` is not `Sort`)
+    e.get_type()?;
+    Ok(e)
+}
+
+pub(crate) fn typecheck(e: Resolved) -> Result<Typed, TypeError> {
+    type_of(e.0)
+}
+
+pub(crate) fn typecheck_with(
+    e: Resolved,
+    ty: &Type,
+) -> Result<Typed, TypeError> {
+    let expr: SubExpr<_, _> = e.0;
+    let ty: SubExpr<_, _> = ty.to_expr().embed_absurd().note_absurd();
+    type_of(expr.rewrap(ExprF::Annot(expr.clone(), ty)))
+}
+pub(crate) fn skip_typecheck(e: Resolved) -> Typed {
+    Typed::from_thunk_untyped(Thunk::new(NormalizationContext::new(), e.0))
+}
+
+/// The specific type error
+#[derive(Debug)]
+pub(crate) enum TypeMessage {
+    UnboundVariable(V<Label>),
+    InvalidInputType(Normalized),
+    InvalidOutputType(Normalized),
+    NotAFunction(Typed),
+    TypeMismatch(Typed, Normalized, Typed),
+    AnnotMismatch(Typed, Normalized),
+    Untyped,
+    InvalidListElement(usize, Normalized, Typed),
+    InvalidListType(Normalized),
+    InvalidOptionalType(Normalized),
+    InvalidPredicate(Typed),
+    IfBranchMismatch(Typed, Typed),
+    IfBranchMustBeTerm(bool, Typed),
+    InvalidFieldType(Label, Type),
+    NotARecord(Label, Normalized),
+    MissingRecordField(Label, Typed),
+    MissingUnionField(Label, Normalized),
+    BinOpTypeMismatch(BinOp, Typed),
+    NoDependentTypes(Normalized, Normalized),
+    InvalidTextInterpolation(Typed),
+    Sort,
+    Unimplemented,
+}
+
+/// A structured type error that includes context
+#[derive(Debug)]
+pub struct TypeError {
+    type_message: TypeMessage,
+    context: TypecheckContext,
+}
+
+impl TypeError {
+    pub(crate) fn new(
+        context: &TypecheckContext,
+        type_message: TypeMessage,
+    ) -> Self {
+        TypeError {
+            context: context.clone(),
+            type_message,
+        }
+    }
+}
+
+impl From<TypeError> for std::option::NoneError {
+    fn from(_: TypeError) -> std::option::NoneError {
+        std::option::NoneError
+    }
+}
+
+impl ::std::error::Error for TypeMessage {
+    fn description(&self) -> &str {
+        match *self {
+            // UnboundVariable => "Unbound variable",
+            InvalidInputType(_) => "Invalid function input",
+            InvalidOutputType(_) => "Invalid function output",
+            NotAFunction(_) => "Not a function",
+            TypeMismatch(_, _, _) => "Wrong type of function argument",
+            _ => "Unhandled error",
+        }
+    }
+}
+
+impl fmt::Display for TypeMessage {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        match self {
+            // UnboundVariable(_) => {
+            //     f.write_str(include_str!("errors/UnboundVariable.txt"))
+            // }
+            // TypeMismatch(e0, e1, e2) => {
+            //     let template = include_str!("errors/TypeMismatch.txt");
+            //     let s = template
+            //         .replace("$txt0", &format!("{}", e0.as_expr()))
+            //         .replace("$txt1", &format!("{}", e1.as_expr()))
+            //         .replace("$txt2", &format!("{}", e2.as_expr()))
+            //         .replace(
+            //             "$txt3",
+            //             &format!(
+            //                 "{}",
+            //                 e2.get_type()
+            //                     .unwrap()
+            //                     .as_normalized()
+            //                     .unwrap()
+            //                     .as_expr()
+            //             ),
+            //         );
+            //     f.write_str(&s)
+            // }
+            _ => f.write_str("Unhandled error message"),
+        }
+    }
+}
+
+#[cfg(test)]
+mod spec_tests {
+    #![rustfmt::skip]
+
+    macro_rules! tc_success {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(Typecheck, Success, $name, $path);
+        };
+    }
+    macro_rules! tc_failure {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(Typecheck, Failure, $name, $path);
+        };
+    }
+
+    macro_rules! ti_success {
+        ($name:ident, $path:expr) => {
+            make_spec_test!(TypeInference, Success, $name, $path);
+        };
+    }
+    // macro_rules! ti_failure {
+    //     ($name:ident, $path:expr) => {
+    //         make_spec_test!(TypeInference, Failure, $name, $path);
+    //     };
+    // }
+
+    // tc_success!(tc_success_accessEncodedType, "accessEncodedType");
+    // tc_success!(tc_success_accessType, "accessType");
+    tc_success!(tc_success_prelude_Bool_and_0, "prelude/Bool/and/0");
+    tc_success!(tc_success_prelude_Bool_and_1, "prelude/Bool/and/1");
+    tc_success!(tc_success_prelude_Bool_build_0, "prelude/Bool/build/0");
+    tc_success!(tc_success_prelude_Bool_build_1, "prelude/Bool/build/1");
+    tc_success!(tc_success_prelude_Bool_even_0, "prelude/Bool/even/0");
+    tc_success!(tc_success_prelude_Bool_even_1, "prelude/Bool/even/1");
+    tc_success!(tc_success_prelude_Bool_even_2, "prelude/Bool/even/2");
+    tc_success!(tc_success_prelude_Bool_even_3, "prelude/Bool/even/3");
+    tc_success!(tc_success_prelude_Bool_fold_0, "prelude/Bool/fold/0");
+    tc_success!(tc_success_prelude_Bool_fold_1, "prelude/Bool/fold/1");
+    tc_success!(tc_success_prelude_Bool_not_0, "prelude/Bool/not/0");
+    tc_success!(tc_success_prelude_Bool_not_1, "prelude/Bool/not/1");
+    tc_success!(tc_success_prelude_Bool_odd_0, "prelude/Bool/odd/0");
+    tc_success!(tc_success_prelude_Bool_odd_1, "prelude/Bool/odd/1");
+    tc_success!(tc_success_prelude_Bool_odd_2, "prelude/Bool/odd/2");
+    tc_success!(tc_success_prelude_Bool_odd_3, "prelude/Bool/odd/3");
+    tc_success!(tc_success_prelude_Bool_or_0, "prelude/Bool/or/0");
+    tc_success!(tc_success_prelude_Bool_or_1, "prelude/Bool/or/1");
+    tc_success!(tc_success_prelude_Bool_show_0, "prelude/Bool/show/0");
+    tc_success!(tc_success_prelude_Bool_show_1, "prelude/Bool/show/1");
+    tc_success!(tc_success_prelude_Double_show_0, "prelude/Double/show/0");
+    tc_success!(tc_success_prelude_Double_show_1, "prelude/Double/show/1");
+    tc_success!(tc_success_prelude_Integer_show_0, "prelude/Integer/show/0");
+    tc_success!(tc_success_prelude_Integer_show_1, "prelude/Integer/show/1");
+    tc_success!(tc_success_prelude_Integer_toDouble_0, "prelude/Integer/toDouble/0");
+    tc_success!(tc_success_prelude_Integer_toDouble_1, "prelude/Integer/toDouble/1");
+    tc_success!(tc_success_prelude_List_all_0, "prelude/List/all/0");
+    tc_success!(tc_success_prelude_List_all_1, "prelude/List/all/1");
+    tc_success!(tc_success_prelude_List_any_0, "prelude/List/any/0");
+    tc_success!(tc_success_prelude_List_any_1, "prelude/List/any/1");
+    tc_success!(tc_success_prelude_List_build_0, "prelude/List/build/0");
+    tc_success!(tc_success_prelude_List_build_1, "prelude/List/build/1");
+    tc_success!(tc_success_prelude_List_concat_0, "prelude/List/concat/0");
+    tc_success!(tc_success_prelude_List_concat_1, "prelude/List/concat/1");
+    tc_success!(tc_success_prelude_List_concatMap_0, "prelude/List/concatMap/0");
+    tc_success!(tc_success_prelude_List_concatMap_1, "prelude/List/concatMap/1");
+    tc_success!(tc_success_prelude_List_filter_0, "prelude/List/filter/0");
+    tc_success!(tc_success_prelude_List_filter_1, "prelude/List/filter/1");
+    tc_success!(tc_success_prelude_List_fold_0, "prelude/List/fold/0");
+    tc_success!(tc_success_prelude_List_fold_1, "prelude/List/fold/1");
+    tc_success!(tc_success_prelude_List_fold_2, "prelude/List/fold/2");
+    tc_success!(tc_success_prelude_List_generate_0, "prelude/List/generate/0");
+    tc_success!(tc_success_prelude_List_generate_1, "prelude/List/generate/1");
+    tc_success!(tc_success_prelude_List_head_0, "prelude/List/head/0");
+    tc_success!(tc_success_prelude_List_head_1, "prelude/List/head/1");
+    tc_success!(tc_success_prelude_List_indexed_0, "prelude/List/indexed/0");
+    tc_success!(tc_success_prelude_List_indexed_1, "prelude/List/indexed/1");
+    tc_success!(tc_success_prelude_List_iterate_0, "prelude/List/iterate/0");
+    tc_success!(tc_success_prelude_List_iterate_1, "prelude/List/iterate/1");
+    tc_success!(tc_success_prelude_List_last_0, "prelude/List/last/0");
+    tc_success!(tc_success_prelude_List_last_1, "prelude/List/last/1");
+    tc_success!(tc_success_prelude_List_length_0, "prelude/List/length/0");
+    tc_success!(tc_success_prelude_List_length_1, "prelude/List/length/1");
+    tc_success!(tc_success_prelude_List_map_0, "prelude/List/map/0");
+    tc_success!(tc_success_prelude_List_map_1, "prelude/List/map/1");
+    tc_success!(tc_success_prelude_List_null_0, "prelude/List/null/0");
+    tc_success!(tc_success_prelude_List_null_1, "prelude/List/null/1");
+    tc_success!(tc_success_prelude_List_replicate_0, "prelude/List/replicate/0");
+    tc_success!(tc_success_prelude_List_replicate_1, "prelude/List/replicate/1");
+    tc_success!(tc_success_prelude_List_reverse_0, "prelude/List/reverse/0");
+    tc_success!(tc_success_prelude_List_reverse_1, "prelude/List/reverse/1");
+    tc_success!(tc_success_prelude_List_shifted_0, "prelude/List/shifted/0");
+    tc_success!(tc_success_prelude_List_shifted_1, "prelude/List/shifted/1");
+    tc_success!(tc_success_prelude_List_unzip_0, "prelude/List/unzip/0");
+    tc_success!(tc_success_prelude_List_unzip_1, "prelude/List/unzip/1");
+    tc_success!(tc_success_prelude_Monoid_00, "prelude/Monoid/00");
+    tc_success!(tc_success_prelude_Monoid_01, "prelude/Monoid/01");
+    tc_success!(tc_success_prelude_Monoid_02, "prelude/Monoid/02");
+    tc_success!(tc_success_prelude_Monoid_03, "prelude/Monoid/03");
+    tc_success!(tc_success_prelude_Monoid_04, "prelude/Monoid/04");
+    tc_success!(tc_success_prelude_Monoid_05, "prelude/Monoid/05");
+    tc_success!(tc_success_prelude_Monoid_06, "prelude/Monoid/06");
+    tc_success!(tc_success_prelude_Monoid_07, "prelude/Monoid/07");
+    tc_success!(tc_success_prelude_Monoid_08, "prelude/Monoid/08");
+    tc_success!(tc_success_prelude_Monoid_09, "prelude/Monoid/09");
+    tc_success!(tc_success_prelude_Monoid_10, "prelude/Monoid/10");
+    tc_success!(tc_success_prelude_Natural_build_0, "prelude/Natural/build/0");
+    tc_success!(tc_success_prelude_Natural_build_1, "prelude/Natural/build/1");
+    tc_success!(tc_success_prelude_Natural_enumerate_0, "prelude/Natural/enumerate/0");
+    tc_success!(tc_success_prelude_Natural_enumerate_1, "prelude/Natural/enumerate/1");
+    tc_success!(tc_success_prelude_Natural_even_0, "prelude/Natural/even/0");
+    tc_success!(tc_success_prelude_Natural_even_1, "prelude/Natural/even/1");
+    tc_success!(tc_success_prelude_Natural_fold_0, "prelude/Natural/fold/0");
+    tc_success!(tc_success_prelude_Natural_fold_1, "prelude/Natural/fold/1");
+    tc_success!(tc_success_prelude_Natural_fold_2, "prelude/Natural/fold/2");
+    tc_success!(tc_success_prelude_Natural_isZero_0, "prelude/Natural/isZero/0");
+    tc_success!(tc_success_prelude_Natural_isZero_1, "prelude/Natural/isZero/1");
+    tc_success!(tc_success_prelude_Natural_odd_0, "prelude/Natural/odd/0");
+    tc_success!(tc_success_prelude_Natural_odd_1, "prelude/Natural/odd/1");
+    tc_success!(tc_success_prelude_Natural_product_0, "prelude/Natural/product/0");
+    tc_success!(tc_success_prelude_Natural_product_1, "prelude/Natural/product/1");
+    tc_success!(tc_success_prelude_Natural_show_0, "prelude/Natural/show/0");
+    tc_success!(tc_success_prelude_Natural_show_1, "prelude/Natural/show/1");
+    tc_success!(tc_success_prelude_Natural_sum_0, "prelude/Natural/sum/0");
+    tc_success!(tc_success_prelude_Natural_sum_1, "prelude/Natural/sum/1");
+    tc_success!(tc_success_prelude_Natural_toDouble_0, "prelude/Natural/toDouble/0");
+    tc_success!(tc_success_prelude_Natural_toDouble_1, "prelude/Natural/toDouble/1");
+    tc_success!(tc_success_prelude_Natural_toInteger_0, "prelude/Natural/toInteger/0");
+    tc_success!(tc_success_prelude_Natural_toInteger_1, "prelude/Natural/toInteger/1");
+    tc_success!(tc_success_prelude_Optional_all_0, "prelude/Optional/all/0");
+    tc_success!(tc_success_prelude_Optional_all_1, "prelude/Optional/all/1");
+    tc_success!(tc_success_prelude_Optional_any_0, "prelude/Optional/any/0");
+    tc_success!(tc_success_prelude_Optional_any_1, "prelude/Optional/any/1");
+    tc_success!(tc_success_prelude_Optional_build_0, "prelude/Optional/build/0");
+    tc_success!(tc_success_prelude_Optional_build_1, "prelude/Optional/build/1");
+    tc_success!(tc_success_prelude_Optional_concat_0, "prelude/Optional/concat/0");
+    tc_success!(tc_success_prelude_Optional_concat_1, "prelude/Optional/concat/1");
+    tc_success!(tc_success_prelude_Optional_concat_2, "prelude/Optional/concat/2");
+    tc_success!(tc_success_prelude_Optional_filter_0, "prelude/Optional/filter/0");
+    tc_success!(tc_success_prelude_Optional_filter_1, "prelude/Optional/filter/1");
+    tc_success!(tc_success_prelude_Optional_fold_0, "prelude/Optional/fold/0");
+    tc_success!(tc_success_prelude_Optional_fold_1, "prelude/Optional/fold/1");
+    tc_success!(tc_success_prelude_Optional_head_0, "prelude/Optional/head/0");
+    tc_success!(tc_success_prelude_Optional_head_1, "prelude/Optional/head/1");
+    tc_success!(tc_success_prelude_Optional_head_2, "prelude/Optional/head/2");
+    tc_success!(tc_success_prelude_Optional_last_0, "prelude/Optional/last/0");
+    tc_success!(tc_success_prelude_Optional_last_1, "prelude/Optional/last/1");
+    tc_success!(tc_success_prelude_Optional_last_2, "prelude/Optional/last/2");
+    tc_success!(tc_success_prelude_Optional_length_0, "prelude/Optional/length/0");
+    tc_success!(tc_success_prelude_Optional_length_1, "prelude/Optional/length/1");
+    tc_success!(tc_success_prelude_Optional_map_0, "prelude/Optional/map/0");
+    tc_success!(tc_success_prelude_Optional_map_1, "prelude/Optional/map/1");
+    tc_success!(tc_success_prelude_Optional_null_0, "prelude/Optional/null/0");
+    tc_success!(tc_success_prelude_Optional_null_1, "prelude/Optional/null/1");
+    tc_success!(tc_success_prelude_Optional_toList_0, "prelude/Optional/toList/0");
+    tc_success!(tc_success_prelude_Optional_toList_1, "prelude/Optional/toList/1");
+    tc_success!(tc_success_prelude_Optional_unzip_0, "prelude/Optional/unzip/0");
+    tc_success!(tc_success_prelude_Optional_unzip_1, "prelude/Optional/unzip/1");
+    tc_success!(tc_success_prelude_Text_concat_0, "prelude/Text/concat/0");
+    tc_success!(tc_success_prelude_Text_concat_1, "prelude/Text/concat/1");
+    tc_success!(tc_success_prelude_Text_concatMap_0, "prelude/Text/concatMap/0");
+    tc_success!(tc_success_prelude_Text_concatMap_1, "prelude/Text/concatMap/1");
+    // tc_success!(tc_success_prelude_Text_concatMapSep_0, "prelude/Text/concatMapSep/0");
+    // tc_success!(tc_success_prelude_Text_concatMapSep_1, "prelude/Text/concatMapSep/1");
+    // tc_success!(tc_success_prelude_Text_concatSep_0, "prelude/Text/concatSep/0");
+    // tc_success!(tc_success_prelude_Text_concatSep_1, "prelude/Text/concatSep/1");
+    tc_success!(tc_success_recordOfRecordOfTypes, "recordOfRecordOfTypes");
+    tc_success!(tc_success_recordOfTypes, "recordOfTypes");
+    // tc_success!(tc_success_simple_access_0, "simple/access/0");
+    // tc_success!(tc_success_simple_access_1, "simple/access/1");
+    // tc_success!(tc_success_simple_alternativesAreTypes, "simple/alternativesAreTypes");
+    // tc_success!(tc_success_simple_anonymousFunctionsInTypes, "simple/anonymousFunctionsInTypes");
+    // tc_success!(tc_success_simple_fieldsAreTypes, "simple/fieldsAreTypes");
+    // tc_success!(tc_success_simple_kindParameter, "simple/kindParameter");
+    // tc_success!(tc_success_simple_mergeEquivalence, "simple/mergeEquivalence");
+    // tc_success!(tc_success_simple_mixedFieldAccess, "simple/mixedFieldAccess");
+    tc_success!(tc_success_simple_unionsOfTypes, "simple/unionsOfTypes");
+
+    tc_failure!(tc_failure_combineMixedRecords, "combineMixedRecords");
+    // tc_failure!(tc_failure_duplicateFields, "duplicateFields");
+    tc_failure!(tc_failure_hurkensParadox, "hurkensParadox");
+    tc_failure!(tc_failure_mixedUnions, "mixedUnions");
+    tc_failure!(tc_failure_preferMixedRecords, "preferMixedRecords");
+    tc_failure!(tc_failure_unit_FunctionApplicationArgumentNotMatch, "unit/FunctionApplicationArgumentNotMatch");
+    tc_failure!(tc_failure_unit_FunctionApplicationIsNotFunction, "unit/FunctionApplicationIsNotFunction");
+    tc_failure!(tc_failure_unit_FunctionArgumentTypeNotAType, "unit/FunctionArgumentTypeNotAType");
+    tc_failure!(tc_failure_unit_FunctionDependentType, "unit/FunctionDependentType");
+    tc_failure!(tc_failure_unit_FunctionDependentType2, "unit/FunctionDependentType2");
+    tc_failure!(tc_failure_unit_FunctionTypeArgumentTypeNotAType, "unit/FunctionTypeArgumentTypeNotAType");
+    tc_failure!(tc_failure_unit_FunctionTypeKindSort, "unit/FunctionTypeKindSort");
+    tc_failure!(tc_failure_unit_FunctionTypeTypeKind, "unit/FunctionTypeTypeKind");
+    tc_failure!(tc_failure_unit_FunctionTypeTypeSort, "unit/FunctionTypeTypeSort");
+    tc_failure!(tc_failure_unit_IfBranchesNotMatch, "unit/IfBranchesNotMatch");
+    tc_failure!(tc_failure_unit_IfBranchesNotType, "unit/IfBranchesNotType");
+    tc_failure!(tc_failure_unit_IfNotBool, "unit/IfNotBool");
+    tc_failure!(tc_failure_unit_LetWithWrongAnnotation, "unit/LetWithWrongAnnotation");
+    tc_failure!(tc_failure_unit_ListLiteralEmptyNotType, "unit/ListLiteralEmptyNotType");
+    tc_failure!(tc_failure_unit_ListLiteralNotType, "unit/ListLiteralNotType");
+    tc_failure!(tc_failure_unit_ListLiteralTypesNotMatch, "unit/ListLiteralTypesNotMatch");
+    tc_failure!(tc_failure_unit_MergeAlternativeHasNoHandler, "unit/MergeAlternativeHasNoHandler");
+    tc_failure!(tc_failure_unit_MergeAnnotationNotType, "unit/MergeAnnotationNotType");
+    tc_failure!(tc_failure_unit_MergeEmptyWithoutAnnotation, "unit/MergeEmptyWithoutAnnotation");
+    tc_failure!(tc_failure_unit_MergeHandlerNotFunction, "unit/MergeHandlerNotFunction");
+    tc_failure!(tc_failure_unit_MergeHandlerNotInUnion, "unit/MergeHandlerNotInUnion");
+    tc_failure!(tc_failure_unit_MergeHandlerNotMatchAlternativeType, "unit/MergeHandlerNotMatchAlternativeType");
+    tc_failure!(tc_failure_unit_MergeHandlersWithDifferentType, "unit/MergeHandlersWithDifferentType");
+    tc_failure!(tc_failure_unit_MergeLhsNotRecord, "unit/MergeLhsNotRecord");
+    tc_failure!(tc_failure_unit_MergeRhsNotUnion, "unit/MergeRhsNotUnion");
+    tc_failure!(tc_failure_unit_MergeWithWrongAnnotation, "unit/MergeWithWrongAnnotation");
+    tc_failure!(tc_failure_unit_OperatorAndNotBool, "unit/OperatorAndNotBool");
+    tc_failure!(tc_failure_unit_OperatorEqualNotBool, "unit/OperatorEqualNotBool");
+    tc_failure!(tc_failure_unit_OperatorListConcatenateLhsNotList, "unit/OperatorListConcatenateLhsNotList");
+    tc_failure!(tc_failure_unit_OperatorListConcatenateListsNotMatch, "unit/OperatorListConcatenateListsNotMatch");
+    tc_failure!(tc_failure_unit_OperatorListConcatenateRhsNotList, "unit/OperatorListConcatenateRhsNotList");
+    tc_failure!(tc_failure_unit_OperatorNotEqualNotBool, "unit/OperatorNotEqualNotBool");
+    tc_failure!(tc_failure_unit_OperatorOrNotBool, "unit/OperatorOrNotBool");
+    tc_failure!(tc_failure_unit_OperatorPlusNotNatural, "unit/OperatorPlusNotNatural");
+    tc_failure!(tc_failure_unit_OperatorTextConcatenateLhsNotText, "unit/OperatorTextConcatenateLhsNotText");
+    tc_failure!(tc_failure_unit_OperatorTextConcatenateRhsNotText, "unit/OperatorTextConcatenateRhsNotText");
+    tc_failure!(tc_failure_unit_OperatorTimesNotNatural, "unit/OperatorTimesNotNatural");
+    tc_failure!(tc_failure_unit_RecordMixedKinds, "unit/RecordMixedKinds");
+    tc_failure!(tc_failure_unit_RecordMixedKinds2, "unit/RecordMixedKinds2");
+    tc_failure!(tc_failure_unit_RecordMixedKinds3, "unit/RecordMixedKinds3");
+    tc_failure!(tc_failure_unit_RecordProjectionEmpty, "unit/RecordProjectionEmpty");
+    tc_failure!(tc_failure_unit_RecordProjectionNotPresent, "unit/RecordProjectionNotPresent");
+    tc_failure!(tc_failure_unit_RecordProjectionNotRecord, "unit/RecordProjectionNotRecord");
+    tc_failure!(tc_failure_unit_RecordSelectionEmpty, "unit/RecordSelectionEmpty");
+    tc_failure!(tc_failure_unit_RecordSelectionNotPresent, "unit/RecordSelectionNotPresent");
+    tc_failure!(tc_failure_unit_RecordSelectionNotRecord, "unit/RecordSelectionNotRecord");
+    tc_failure!(tc_failure_unit_RecordSelectionTypeNotUnionType, "unit/RecordSelectionTypeNotUnionType");
+    tc_failure!(tc_failure_unit_RecordTypeMixedKinds, "unit/RecordTypeMixedKinds");
+    tc_failure!(tc_failure_unit_RecordTypeMixedKinds2, "unit/RecordTypeMixedKinds2");
+    tc_failure!(tc_failure_unit_RecordTypeMixedKinds3, "unit/RecordTypeMixedKinds3");
+    tc_failure!(tc_failure_unit_RecordTypeValueMember, "unit/RecordTypeValueMember");
+    tc_failure!(tc_failure_unit_RecursiveRecordMergeLhsNotRecord, "unit/RecursiveRecordMergeLhsNotRecord");
+    tc_failure!(tc_failure_unit_RecursiveRecordMergeMixedKinds, "unit/RecursiveRecordMergeMixedKinds");
+    tc_failure!(tc_failure_unit_RecursiveRecordMergeOverlapping, "unit/RecursiveRecordMergeOverlapping");
+    tc_failure!(tc_failure_unit_RecursiveRecordMergeRhsNotRecord, "unit/RecursiveRecordMergeRhsNotRecord");
+    tc_failure!(tc_failure_unit_RecursiveRecordTypeMergeLhsNotRecordType, "unit/RecursiveRecordTypeMergeLhsNotRecordType");
+    tc_failure!(tc_failure_unit_RecursiveRecordTypeMergeOverlapping, "unit/RecursiveRecordTypeMergeOverlapping");
+    tc_failure!(tc_failure_unit_RecursiveRecordTypeMergeRhsNotRecordType, "unit/RecursiveRecordTypeMergeRhsNotRecordType");
+    tc_failure!(tc_failure_unit_RightBiasedRecordMergeLhsNotRecord, "unit/RightBiasedRecordMergeLhsNotRecord");
+    tc_failure!(tc_failure_unit_RightBiasedRecordMergeMixedKinds, "unit/RightBiasedRecordMergeMixedKinds");
+    tc_failure!(tc_failure_unit_RightBiasedRecordMergeMixedKinds2, "unit/RightBiasedRecordMergeMixedKinds2");
+    tc_failure!(tc_failure_unit_RightBiasedRecordMergeMixedKinds3, "unit/RightBiasedRecordMergeMixedKinds3");
+    tc_failure!(tc_failure_unit_RightBiasedRecordMergeRhsNotRecord, "unit/RightBiasedRecordMergeRhsNotRecord");
+    tc_failure!(tc_failure_unit_SomeNotType, "unit/SomeNotType");
+    tc_failure!(tc_failure_unit_Sort, "unit/Sort");
+    tc_failure!(tc_failure_unit_TextLiteralInterpolateNotText, "unit/TextLiteralInterpolateNotText");
+    tc_failure!(tc_failure_unit_TypeAnnotationWrong, "unit/TypeAnnotationWrong");
+    tc_failure!(tc_failure_unit_UnionConstructorFieldNotPresent, "unit/UnionConstructorFieldNotPresent");
+    tc_failure!(tc_failure_unit_UnionTypeMixedKinds, "unit/UnionTypeMixedKinds");
+    tc_failure!(tc_failure_unit_UnionTypeMixedKinds2, "unit/UnionTypeMixedKinds2");
+    tc_failure!(tc_failure_unit_UnionTypeMixedKinds3, "unit/UnionTypeMixedKinds3");
+    tc_failure!(tc_failure_unit_UnionTypeNotType, "unit/UnionTypeNotType");
+    tc_failure!(tc_failure_unit_VariableFree, "unit/VariableFree");
+
+    // ti_success!(ti_success_simple_alternativesAreTypes, "simple/alternativesAreTypes");
+    // ti_success!(ti_success_simple_kindParameter, "simple/kindParameter");
+    ti_success!(ti_success_unit_Bool, "unit/Bool");
+    ti_success!(ti_success_unit_Double, "unit/Double");
+    ti_success!(ti_success_unit_DoubleLiteral, "unit/DoubleLiteral");
+    ti_success!(ti_success_unit_DoubleShow, "unit/DoubleShow");
+    ti_success!(ti_success_unit_False, "unit/False");
+    ti_success!(ti_success_unit_Function, "unit/Function");
+    ti_success!(ti_success_unit_FunctionApplication, "unit/FunctionApplication");
+    ti_success!(ti_success_unit_FunctionNamedArg, "unit/FunctionNamedArg");
+    ti_success!(ti_success_unit_FunctionTypeKindKind, "unit/FunctionTypeKindKind");
+    ti_success!(ti_success_unit_FunctionTypeKindTerm, "unit/FunctionTypeKindTerm");
+    ti_success!(ti_success_unit_FunctionTypeKindType, "unit/FunctionTypeKindType");
+    ti_success!(ti_success_unit_FunctionTypeTermTerm, "unit/FunctionTypeTermTerm");
+    ti_success!(ti_success_unit_FunctionTypeTypeTerm, "unit/FunctionTypeTypeTerm");
+    ti_success!(ti_success_unit_FunctionTypeTypeType, "unit/FunctionTypeTypeType");
+    ti_success!(ti_success_unit_FunctionTypeUsingArgument, "unit/FunctionTypeUsingArgument");
+    ti_success!(ti_success_unit_If, "unit/If");
+    ti_success!(ti_success_unit_IfNormalizeArguments, "unit/IfNormalizeArguments");
+    ti_success!(ti_success_unit_Integer, "unit/Integer");
+    ti_success!(ti_success_unit_IntegerLiteral, "unit/IntegerLiteral");
+    ti_success!(ti_success_unit_IntegerShow, "unit/IntegerShow");
+    ti_success!(ti_success_unit_IntegerToDouble, "unit/IntegerToDouble");
+    ti_success!(ti_success_unit_Kind, "unit/Kind");
+    ti_success!(ti_success_unit_Let, "unit/Let");
+    ti_success!(ti_success_unit_LetNestedTypeSynonym, "unit/LetNestedTypeSynonym");
+    ti_success!(ti_success_unit_LetTypeSynonym, "unit/LetTypeSynonym");
+    ti_success!(ti_success_unit_LetWithAnnotation, "unit/LetWithAnnotation");
+    ti_success!(ti_success_unit_List, "unit/List");
+    ti_success!(ti_success_unit_ListBuild, "unit/ListBuild");
+    ti_success!(ti_success_unit_ListFold, "unit/ListFold");
+    ti_success!(ti_success_unit_ListHead, "unit/ListHead");
+    ti_success!(ti_success_unit_ListIndexed, "unit/ListIndexed");
+    ti_success!(ti_success_unit_ListLast, "unit/ListLast");
+    ti_success!(ti_success_unit_ListLength, "unit/ListLength");
+    ti_success!(ti_success_unit_ListLiteralEmpty, "unit/ListLiteralEmpty");
+    ti_success!(ti_success_unit_ListLiteralNormalizeArguments, "unit/ListLiteralNormalizeArguments");
+    ti_success!(ti_success_unit_ListLiteralOne, "unit/ListLiteralOne");
+    ti_success!(ti_success_unit_ListReverse, "unit/ListReverse");
+    // ti_success!(ti_success_unit_MergeEmptyUnion, "unit/MergeEmptyUnion");
+    // ti_success!(ti_success_unit_MergeOne, "unit/MergeOne");
+    // ti_success!(ti_success_unit_MergeOneWithAnnotation, "unit/MergeOneWithAnnotation");
+    ti_success!(ti_success_unit_Natural, "unit/Natural");
+    ti_success!(ti_success_unit_NaturalBuild, "unit/NaturalBuild");
+    ti_success!(ti_success_unit_NaturalEven, "unit/NaturalEven");
+    ti_success!(ti_success_unit_NaturalFold, "unit/NaturalFold");
+    ti_success!(ti_success_unit_NaturalIsZero, "unit/NaturalIsZero");
+    ti_success!(ti_success_unit_NaturalLiteral, "unit/NaturalLiteral");
+    ti_success!(ti_success_unit_NaturalOdd, "unit/NaturalOdd");
+    ti_success!(ti_success_unit_NaturalShow, "unit/NaturalShow");
+    ti_success!(ti_success_unit_NaturalToInteger, "unit/NaturalToInteger");
+    ti_success!(ti_success_unit_None, "unit/None");
+    ti_success!(ti_success_unit_OldOptionalNone, "unit/OldOptionalNone");
+    ti_success!(ti_success_unit_OldOptionalTrue, "unit/OldOptionalTrue");
+    ti_success!(ti_success_unit_OperatorAnd, "unit/OperatorAnd");
+    ti_success!(ti_success_unit_OperatorAndNormalizeArguments, "unit/OperatorAndNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorEqual, "unit/OperatorEqual");
+    ti_success!(ti_success_unit_OperatorEqualNormalizeArguments, "unit/OperatorEqualNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorListConcatenate, "unit/OperatorListConcatenate");
+    ti_success!(ti_success_unit_OperatorListConcatenateNormalizeArguments, "unit/OperatorListConcatenateNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorNotEqual, "unit/OperatorNotEqual");
+    ti_success!(ti_success_unit_OperatorNotEqualNormalizeArguments, "unit/OperatorNotEqualNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorOr, "unit/OperatorOr");
+    ti_success!(ti_success_unit_OperatorOrNormalizeArguments, "unit/OperatorOrNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorPlus, "unit/OperatorPlus");
+    ti_success!(ti_success_unit_OperatorPlusNormalizeArguments, "unit/OperatorPlusNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorTextConcatenate, "unit/OperatorTextConcatenate");
+    ti_success!(ti_success_unit_OperatorTextConcatenateNormalizeArguments, "unit/OperatorTextConcatenateNormalizeArguments");
+    ti_success!(ti_success_unit_OperatorTimes, "unit/OperatorTimes");
+    ti_success!(ti_success_unit_OperatorTimesNormalizeArguments, "unit/OperatorTimesNormalizeArguments");
+    ti_success!(ti_success_unit_Optional, "unit/Optional");
+    ti_success!(ti_success_unit_OptionalBuild, "unit/OptionalBuild");
+    ti_success!(ti_success_unit_OptionalFold, "unit/OptionalFold");
+    ti_success!(ti_success_unit_RecordEmpty, "unit/RecordEmpty");
+    ti_success!(ti_success_unit_RecordOneKind, "unit/RecordOneKind");
+    ti_success!(ti_success_unit_RecordOneType, "unit/RecordOneType");
+    ti_success!(ti_success_unit_RecordOneValue, "unit/RecordOneValue");
+    // ti_success!(ti_success_unit_RecordProjectionEmpty, "unit/RecordProjectionEmpty");
+    // ti_success!(ti_success_unit_RecordProjectionKind, "unit/RecordProjectionKind");
+    // ti_success!(ti_success_unit_RecordProjectionType, "unit/RecordProjectionType");
+    // ti_success!(ti_success_unit_RecordProjectionValue, "unit/RecordProjectionValue");
+    // ti_success!(ti_success_unit_RecordSelectionKind, "unit/RecordSelectionKind");
+    // ti_success!(ti_success_unit_RecordSelectionType, "unit/RecordSelectionType");
+    ti_success!(ti_success_unit_RecordSelectionValue, "unit/RecordSelectionValue");
+    ti_success!(ti_success_unit_RecordType, "unit/RecordType");
+    ti_success!(ti_success_unit_RecordTypeEmpty, "unit/RecordTypeEmpty");
+    ti_success!(ti_success_unit_RecordTypeKind, "unit/RecordTypeKind");
+    ti_success!(ti_success_unit_RecordTypeType, "unit/RecordTypeType");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeLhsEmpty, "unit/RecursiveRecordMergeLhsEmpty");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeRecursively, "unit/RecursiveRecordMergeRecursively");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeRecursivelyTypes, "unit/RecursiveRecordMergeRecursivelyTypes");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeRhsEmpty, "unit/RecursiveRecordMergeRhsEmpty");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeTwo, "unit/RecursiveRecordMergeTwo");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeTwoKinds, "unit/RecursiveRecordMergeTwoKinds");
+    // ti_success!(ti_success_unit_RecursiveRecordMergeTwoTypes, "unit/RecursiveRecordMergeTwoTypes");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeRecursively, "unit/RecursiveRecordTypeMergeRecursively");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeRecursivelyTypes, "unit/RecursiveRecordTypeMergeRecursivelyTypes");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeRhsEmpty, "unit/RecursiveRecordTypeMergeRhsEmpty");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwo, "unit/RecursiveRecordTypeMergeTwo");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwoKinds, "unit/RecursiveRecordTypeMergeTwoKinds");
+    // ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwoTypes, "unit/RecursiveRecordTypeMergeTwoTypes");
+    // ti_success!(ti_success_unit_RightBiasedRecordMergeRhsEmpty, "unit/RightBiasedRecordMergeRhsEmpty");
+    // ti_success!(ti_success_unit_RightBiasedRecordMergeTwo, "unit/RightBiasedRecordMergeTwo");
+    // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoDifferent, "unit/RightBiasedRecordMergeTwoDifferent");
+    // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoKinds, "unit/RightBiasedRecordMergeTwoKinds");
+    // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoTypes, "unit/RightBiasedRecordMergeTwoTypes");
+    ti_success!(ti_success_unit_SomeTrue, "unit/SomeTrue");
+    ti_success!(ti_success_unit_Text, "unit/Text");
+    ti_success!(ti_success_unit_TextLiteral, "unit/TextLiteral");
+    ti_success!(ti_success_unit_TextLiteralNormalizeArguments, "unit/TextLiteralNormalizeArguments");
+    ti_success!(ti_success_unit_TextLiteralWithInterpolation, "unit/TextLiteralWithInterpolation");
+    ti_success!(ti_success_unit_TextShow, "unit/TextShow");
+    ti_success!(ti_success_unit_True, "unit/True");
+    ti_success!(ti_success_unit_Type, "unit/Type");
+    ti_success!(ti_success_unit_TypeAnnotation, "unit/TypeAnnotation");
+    ti_success!(ti_success_unit_TypeAnnotationSort, "unit/TypeAnnotationSort");
+    ti_success!(ti_success_unit_UnionConstructorField, "unit/UnionConstructorField");
+    ti_success!(ti_success_unit_UnionOne, "unit/UnionOne");
+    ti_success!(ti_success_unit_UnionTypeEmpty, "unit/UnionTypeEmpty");
+    ti_success!(ti_success_unit_UnionTypeKind, "unit/UnionTypeKind");
+    ti_success!(ti_success_unit_UnionTypeOne, "unit/UnionTypeOne");
+    ti_success!(ti_success_unit_UnionTypeType, "unit/UnionTypeType");
+}
-- 
cgit v1.2.3