Introduce LitKind to factor out common enum nodes

10 files changed, 179 insertions, 158 deletions

diff --git a/dhall/src/semantics/builtins.rs b/dhall/src/semantics/builtins.rs
index cbb5a6e..752b25c 100644
--- a/dhall/src/semantics/builtins.rs
+++ b/dhall/src/semantics/builtins.rs
@@ -5,7 +5,8 @@ use crate::syntax::map::DupTreeMap;
 use crate::syntax::Const::Type;
 use crate::syntax::{
     BinOp, Builtin, Const, Expr, ExprKind, InterpolatedText,
-    InterpolatedTextContents, Label, NaiveDouble, Span, UnspannedExpr, V,
+    InterpolatedTextContents, Label, LitKind, NaiveDouble, Span, UnspannedExpr,
+    V,
 };
 use crate::Normalized;
 use std::collections::HashMap;
@@ -240,7 +241,7 @@ macro_rules! make_closure {
         rc(ExprKind::BinOp(
             BinOp::NaturalPlus,
             make_closure!($($v)*),
-            rc(ExprKind::NaturalLit(1))
+            rc(ExprKind::Lit(LitKind::Natural(1)))
         ))
     };
     ([ $($head:tt)* ] # $($tail:tt)*) => {{
@@ -256,7 +257,7 @@ macro_rules! make_closure {
 
 #[allow(clippy::cognitive_complexity)]
 fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
-    use Builtin::*;
+    use LitKind::{Bool, Double, Integer, Natural};
     use ValueKind::*;
 
     // Small helper enum
@@ -272,38 +273,40 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
     };
 
     let ret = match (b, args.as_slice()) {
-        (OptionalNone, [t]) => Ret::ValueKind(EmptyOptionalLit(t.clone())),
-        (NaturalIsZero, [n]) => match &*n.kind() {
-            NaturalLit(n) => Ret::ValueKind(BoolLit(*n == 0)),
+        (Builtin::OptionalNone, [t]) => {
+            Ret::ValueKind(EmptyOptionalLit(t.clone()))
+        }
+        (Builtin::NaturalIsZero, [n]) => match &*n.kind() {
+            Lit(Natural(n)) => Ret::ValueKind(Lit(Bool(*n == 0))),
             _ => Ret::DoneAsIs,
         },
-        (NaturalEven, [n]) => match &*n.kind() {
-            NaturalLit(n) => Ret::ValueKind(BoolLit(*n % 2 == 0)),
+        (Builtin::NaturalEven, [n]) => match &*n.kind() {
+            Lit(Natural(n)) => Ret::ValueKind(Lit(Bool(*n % 2 == 0))),
             _ => Ret::DoneAsIs,
         },
-        (NaturalOdd, [n]) => match &*n.kind() {
-            NaturalLit(n) => Ret::ValueKind(BoolLit(*n % 2 != 0)),
+        (Builtin::NaturalOdd, [n]) => match &*n.kind() {
+            Lit(Natural(n)) => Ret::ValueKind(Lit(Bool(*n % 2 != 0))),
             _ => Ret::DoneAsIs,
         },
-        (NaturalToInteger, [n]) => match &*n.kind() {
-            NaturalLit(n) => Ret::ValueKind(IntegerLit(*n as isize)),
+        (Builtin::NaturalToInteger, [n]) => match &*n.kind() {
+            Lit(Natural(n)) => Ret::ValueKind(Lit(Integer(*n as isize))),
             _ => Ret::DoneAsIs,
         },
-        (NaturalShow, [n]) => match &*n.kind() {
-            NaturalLit(n) => Ret::Value(Value::from_text(n)),
+        (Builtin::NaturalShow, [n]) => match &*n.kind() {
+            Lit(Natural(n)) => Ret::Value(Value::from_text(n)),
             _ => Ret::DoneAsIs,
         },
-        (NaturalSubtract, [a, b]) => match (&*a.kind(), &*b.kind()) {
-            (NaturalLit(a), NaturalLit(b)) => {
-                Ret::ValueKind(NaturalLit(if b > a { b - a } else { 0 }))
+        (Builtin::NaturalSubtract, [a, b]) => match (&*a.kind(), &*b.kind()) {
+            (Lit(Natural(a)), Lit(Natural(b))) => {
+                Ret::ValueKind(Lit(Natural(if b > a { b - a } else { 0 })))
             }
-            (NaturalLit(0), _) => Ret::Value(b.clone()),
-            (_, NaturalLit(0)) => Ret::ValueKind(NaturalLit(0)),
-            _ if a == b => Ret::ValueKind(NaturalLit(0)),
+            (Lit(Natural(0)), _) => Ret::Value(b.clone()),
+            (_, Lit(Natural(0))) => Ret::ValueKind(Lit(Natural(0))),
+            _ if a == b => Ret::ValueKind(Lit(Natural(0))),
             _ => Ret::DoneAsIs,
         },
-        (IntegerShow, [n]) => match &*n.kind() {
-            IntegerLit(n) => {
+        (Builtin::IntegerShow, [n]) => match &*n.kind() {
+            Lit(Integer(n)) => {
                 let s = if *n < 0 {
                     n.to_string()
                 } else {
@@ -313,27 +316,27 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
             }
             _ => Ret::DoneAsIs,
         },
-        (IntegerToDouble, [n]) => match &*n.kind() {
-            IntegerLit(n) => {
-                Ret::ValueKind(DoubleLit(NaiveDouble::from(*n as f64)))
+        (Builtin::IntegerToDouble, [n]) => match &*n.kind() {
+            Lit(Integer(n)) => {
+                Ret::ValueKind(Lit(Double(NaiveDouble::from(*n as f64))))
             }
             _ => Ret::DoneAsIs,
         },
-        (IntegerNegate, [n]) => match &*n.kind() {
-            IntegerLit(n) => Ret::ValueKind(IntegerLit(-n)),
+        (Builtin::IntegerNegate, [n]) => match &*n.kind() {
+            Lit(Integer(n)) => Ret::ValueKind(Lit(Integer(-n))),
             _ => Ret::DoneAsIs,
         },
-        (IntegerClamp, [n]) => match &*n.kind() {
-            IntegerLit(n) => {
-                Ret::ValueKind(NaturalLit((*n).try_into().unwrap_or(0)))
+        (Builtin::IntegerClamp, [n]) => match &*n.kind() {
+            Lit(Integer(n)) => {
+                Ret::ValueKind(Lit(Natural((*n).try_into().unwrap_or(0))))
             }
             _ => Ret::DoneAsIs,
         },
-        (DoubleShow, [n]) => match &*n.kind() {
-            DoubleLit(n) => Ret::Value(Value::from_text(n)),
+        (Builtin::DoubleShow, [n]) => match &*n.kind() {
+            Lit(Double(n)) => Ret::Value(Value::from_text(n)),
             _ => Ret::DoneAsIs,
         },
-        (TextShow, [v]) => match &*v.kind() {
+        (Builtin::TextShow, [v]) => match &*v.kind() {
             TextLit(tlit) => {
                 if let Some(s) = tlit.as_text() {
                     // Printing InterpolatedText takes care of all the escaping
@@ -347,38 +350,41 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
             }
             _ => Ret::DoneAsIs,
         },
-        (ListLength, [_, l]) => match &*l.kind() {
-            EmptyListLit(_) => Ret::ValueKind(NaturalLit(0)),
-            NEListLit(xs) => Ret::ValueKind(NaturalLit(xs.len())),
+        (Builtin::ListLength, [_, l]) => match &*l.kind() {
+            EmptyListLit(_) => Ret::ValueKind(Lit(Natural(0))),
+            NEListLit(xs) => Ret::ValueKind(Lit(Natural(xs.len()))),
             _ => Ret::DoneAsIs,
         },
-        (ListHead, [_, l]) => match &*l.kind() {
+        (Builtin::ListHead, [_, l]) => match &*l.kind() {
             EmptyListLit(n) => Ret::ValueKind(EmptyOptionalLit(n.clone())),
             NEListLit(xs) => {
                 Ret::ValueKind(NEOptionalLit(xs.iter().next().unwrap().clone()))
             }
             _ => Ret::DoneAsIs,
         },
-        (ListLast, [_, l]) => match &*l.kind() {
+        (Builtin::ListLast, [_, l]) => match &*l.kind() {
             EmptyListLit(n) => Ret::ValueKind(EmptyOptionalLit(n.clone())),
             NEListLit(xs) => Ret::ValueKind(NEOptionalLit(
                 xs.iter().rev().next().unwrap().clone(),
             )),
             _ => Ret::DoneAsIs,
         },
-        (ListReverse, [_, l]) => match &*l.kind() {
+        (Builtin::ListReverse, [_, l]) => match &*l.kind() {
             EmptyListLit(n) => Ret::ValueKind(EmptyListLit(n.clone())),
             NEListLit(xs) => {
                 Ret::ValueKind(NEListLit(xs.iter().rev().cloned().collect()))
             }
             _ => Ret::DoneAsIs,
         },
-        (ListIndexed, [t, l]) => {
+        (Builtin::ListIndexed, [t, l]) => {
             match l.kind() {
                 EmptyListLit(_) | NEListLit(_) => {
                     // Construct the returned record type: { index: Natural, value: t }
                     let mut kts = HashMap::new();
-                    kts.insert("index".into(), Value::from_builtin(Natural));
+                    kts.insert(
+                        "index".into(),
+                        Value::from_builtin(Builtin::Natural),
+                    );
                     kts.insert("value".into(), t.clone());
                     let t = Value::from_kind(RecordType(kts));
 
@@ -392,7 +398,7 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
                                     let mut kvs = HashMap::new();
                                     kvs.insert(
                                         "index".into(),
-                                        Value::from_kind(NaturalLit(i)),
+                                        Value::from_kind(Lit(Natural(i))),
                                     );
                                     kvs.insert("value".into(), e.clone());
                                     Value::from_kind(RecordLit(kvs))
@@ -406,8 +412,8 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
                 _ => Ret::DoneAsIs,
             }
         }
-        (ListBuild, [t, f]) => {
-            let list_t = Value::from_builtin(List).app(t.clone());
+        (Builtin::ListBuild, [t, f]) => {
+            let list_t = Value::from_builtin(Builtin::List).app(t.clone());
             Ret::Value(
                 f.app(list_t.clone())
                     .app(
@@ -422,7 +428,7 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
                     .app(EmptyListLit(t.clone()).into_value()),
             )
         }
-        (ListFold, [_, l, _, cons, nil]) => match &*l.kind() {
+        (Builtin::ListFold, [_, l, _, cons, nil]) => match &*l.kind() {
             EmptyListLit(_) => Ret::Value(nil.clone()),
             NEListLit(xs) => {
                 let mut v = nil.clone();
@@ -433,8 +439,9 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
             }
             _ => Ret::DoneAsIs,
         },
-        (OptionalBuild, [t, f]) => {
-            let optional_t = Value::from_builtin(Optional).app(t.clone());
+        (Builtin::OptionalBuild, [t, f]) => {
+            let optional_t =
+                Value::from_builtin(Builtin::Optional).app(t.clone());
             Ret::Value(
                 f.app(optional_t.clone())
                     .app(
@@ -448,25 +455,25 @@ fn apply_builtin(b: Builtin, args: Vec<Value>, env: NzEnv) -> ValueKind {
                     .app(EmptyOptionalLit(t.clone()).into_value()),
             )
         }
-        (OptionalFold, [_, v, _, just, nothing]) => match &*v.kind() {
+        (Builtin::OptionalFold, [_, v, _, just, nothing]) => match &*v.kind() {
             EmptyOptionalLit(_) => Ret::Value(nothing.clone()),
             NEOptionalLit(x) => Ret::Value(just.app(x.clone())),
             _ => Ret::DoneAsIs,
         },
-        (NaturalBuild, [f]) => Ret::Value(
-            f.app(Value::from_builtin(Natural))
+        (Builtin::NaturalBuild, [f]) => Ret::Value(
+            f.app(Value::from_builtin(Builtin::Natural))
                 .app(make_closure(make_closure!(
                     λ(x : Natural) ->
                     1 + var(x)
                 )))
-                .app(NaturalLit(0).into_value()),
+                .app(Lit(Natural(0)).into_value()),
         ),
 
-        (NaturalFold, [n, t, succ, zero]) => match &*n.kind() {
-            NaturalLit(0) => Ret::Value(zero.clone()),
-            NaturalLit(n) => {
-                let fold = Value::from_builtin(NaturalFold)
-                    .app(NaturalLit(n - 1).into_value())
+        (Builtin::NaturalFold, [n, t, succ, zero]) => match &*n.kind() {
+            Lit(Natural(0)) => Ret::Value(zero.clone()),
+            Lit(Natural(n)) => {
+                let fold = Value::from_builtin(Builtin::NaturalFold)
+                    .app(Lit(Natural(n - 1)).into_value())
                     .app(t.clone())
                     .app(succ.clone())
                     .app(zero.clone());
diff --git a/dhall/src/semantics/nze/normalize.rs b/dhall/src/semantics/nze/normalize.rs
index 03b91a5..4111190 100644
--- a/dhall/src/semantics/nze/normalize.rs
+++ b/dhall/src/semantics/nze/normalize.rs
@@ -5,7 +5,9 @@ use crate::semantics::NzEnv;
 use crate::semantics::{
     Binder, BuiltinClosure, Closure, Hir, HirKind, TextLit, Value, ValueKind,
 };
-use crate::syntax::{BinOp, Builtin, ExprKind, InterpolatedTextContents};
+use crate::syntax::{
+    BinOp, Builtin, ExprKind, InterpolatedTextContents, LitKind,
+};
 
 pub(crate) fn apply_any(f: Value, a: Value) -> ValueKind {
     match f.kind() {
@@ -98,40 +100,44 @@ fn apply_binop<'a>(o: BinOp, x: &'a Value, y: &'a Value) -> Option<Ret<'a>> {
         NaturalTimes, RecursiveRecordMerge, RecursiveRecordTypeMerge,
         RightBiasedRecordMerge, TextAppend,
     };
-    use ValueKind::{
-        BoolLit, EmptyListLit, NEListLit, NaturalLit, RecordLit, RecordType,
-    };
+    use LitKind::{Bool, Natural};
+    use ValueKind::{EmptyListLit, Lit, NEListLit, RecordLit, RecordType};
+
     Some(match (o, x.kind(), y.kind()) {
-        (BoolAnd, BoolLit(true), _) => Ret::ValueRef(y),
-        (BoolAnd, _, BoolLit(true)) => Ret::ValueRef(x),
-        (BoolAnd, BoolLit(false), _) => Ret::ValueKind(BoolLit(false)),
-        (BoolAnd, _, BoolLit(false)) => Ret::ValueKind(BoolLit(false)),
+        (BoolAnd, Lit(Bool(true)), _) => Ret::ValueRef(y),
+        (BoolAnd, _, Lit(Bool(true))) => Ret::ValueRef(x),
+        (BoolAnd, Lit(Bool(false)), _) => Ret::ValueKind(Lit(Bool(false))),
+        (BoolAnd, _, Lit(Bool(false))) => Ret::ValueKind(Lit(Bool(false))),
         (BoolAnd, _, _) if x == y => Ret::ValueRef(x),
-        (BoolOr, BoolLit(true), _) => Ret::ValueKind(BoolLit(true)),
-        (BoolOr, _, BoolLit(true)) => Ret::ValueKind(BoolLit(true)),
-        (BoolOr, BoolLit(false), _) => Ret::ValueRef(y),
-        (BoolOr, _, BoolLit(false)) => Ret::ValueRef(x),
+        (BoolOr, Lit(Bool(true)), _) => Ret::ValueKind(Lit(Bool(true))),
+        (BoolOr, _, Lit(Bool(true))) => Ret::ValueKind(Lit(Bool(true))),
+        (BoolOr, Lit(Bool(false)), _) => Ret::ValueRef(y),
+        (BoolOr, _, Lit(Bool(false))) => Ret::ValueRef(x),
         (BoolOr, _, _) if x == y => Ret::ValueRef(x),
-        (BoolEQ, BoolLit(true), _) => Ret::ValueRef(y),
-        (BoolEQ, _, BoolLit(true)) => Ret::ValueRef(x),
-        (BoolEQ, BoolLit(x), BoolLit(y)) => Ret::ValueKind(BoolLit(x == y)),
-        (BoolEQ, _, _) if x == y => Ret::ValueKind(BoolLit(true)),
-        (BoolNE, BoolLit(false), _) => Ret::ValueRef(y),
-        (BoolNE, _, BoolLit(false)) => Ret::ValueRef(x),
-        (BoolNE, BoolLit(x), BoolLit(y)) => Ret::ValueKind(BoolLit(x != y)),
-        (BoolNE, _, _) if x == y => Ret::ValueKind(BoolLit(false)),
+        (BoolEQ, Lit(Bool(true)), _) => Ret::ValueRef(y),
+        (BoolEQ, _, Lit(Bool(true))) => Ret::ValueRef(x),
+        (BoolEQ, Lit(Bool(x)), Lit(Bool(y))) => {
+            Ret::ValueKind(Lit(Bool(x == y)))
+        }
+        (BoolEQ, _, _) if x == y => Ret::ValueKind(Lit(Bool(true))),
+        (BoolNE, Lit(Bool(false)), _) => Ret::ValueRef(y),
+        (BoolNE, _, Lit(Bool(false))) => Ret::ValueRef(x),
+        (BoolNE, Lit(Bool(x)), Lit(Bool(y))) => {
+            Ret::ValueKind(Lit(Bool(x != y)))
+        }
+        (BoolNE, _, _) if x == y => Ret::ValueKind(Lit(Bool(false))),
 
-        (NaturalPlus, NaturalLit(0), _) => Ret::ValueRef(y),
-        (NaturalPlus, _, NaturalLit(0)) => Ret::ValueRef(x),
-        (NaturalPlus, NaturalLit(x), NaturalLit(y)) => {
-            Ret::ValueKind(NaturalLit(x + y))
-        }
-        (NaturalTimes, NaturalLit(0), _) => Ret::ValueKind(NaturalLit(0)),
-        (NaturalTimes, _, NaturalLit(0)) => Ret::ValueKind(NaturalLit(0)),
-        (NaturalTimes, NaturalLit(1), _) => Ret::ValueRef(y),
-        (NaturalTimes, _, NaturalLit(1)) => Ret::ValueRef(x),
-        (NaturalTimes, NaturalLit(x), NaturalLit(y)) => {
-            Ret::ValueKind(NaturalLit(x * y))
+        (NaturalPlus, Lit(Natural(0)), _) => Ret::ValueRef(y),
+        (NaturalPlus, _, Lit(Natural(0))) => Ret::ValueRef(x),
+        (NaturalPlus, Lit(Natural(x)), Lit(Natural(y))) => {
+            Ret::ValueKind(Lit(Natural(x + y)))
+        }
+        (NaturalTimes, Lit(Natural(0)), _) => Ret::ValueKind(Lit(Natural(0))),
+        (NaturalTimes, _, Lit(Natural(0))) => Ret::ValueKind(Lit(Natural(0))),
+        (NaturalTimes, Lit(Natural(1)), _) => Ret::ValueRef(y),
+        (NaturalTimes, _, Lit(Natural(1))) => Ret::ValueRef(x),
+        (NaturalTimes, Lit(Natural(x)), Lit(Natural(y))) => {
+            Ret::ValueKind(Lit(Natural(x * y)))
         }
 
         (ListAppend, EmptyListLit(_), _) => Ret::ValueRef(y),
@@ -217,10 +223,11 @@ pub(crate) fn normalize_one_layer(
     expr: ExprKind<Value>,
     env: &NzEnv,
 ) -> ValueKind {
+    use LitKind::Bool;
     use ValueKind::{
-        BoolLit, DoubleLit, EmptyListLit, EmptyOptionalLit, IntegerLit,
-        NEListLit, NEOptionalLit, NaturalLit, PartialExpr, RecordLit,
-        RecordType, UnionConstructor, UnionLit, UnionType,
+        EmptyListLit, EmptyOptionalLit, Lit, NEListLit, NEOptionalLit,
+        PartialExpr, RecordLit, RecordType, UnionConstructor, UnionLit,
+        UnionType,
     };
 
     let ret = match expr {
@@ -240,10 +247,7 @@ pub(crate) fn normalize_one_layer(
         ExprKind::Builtin(b) => Ret::Value(Value::from_builtin_env(b, env)),
         ExprKind::Assert(_) => Ret::Expr(expr),
         ExprKind::App(v, a) => Ret::Value(v.app(a)),
-        ExprKind::BoolLit(b) => Ret::ValueKind(BoolLit(b)),
-        ExprKind::NaturalLit(n) => Ret::ValueKind(NaturalLit(n)),
-        ExprKind::IntegerLit(n) => Ret::ValueKind(IntegerLit(n)),
-        ExprKind::DoubleLit(n) => Ret::ValueKind(DoubleLit(n)),
+        ExprKind::Lit(l) => Ret::ValueKind(Lit(l.clone())),
         ExprKind::SomeLit(e) => Ret::ValueKind(NEOptionalLit(e)),
         ExprKind::EmptyListLit(t) => {
             let arg = match t.kind() {
@@ -279,12 +283,12 @@ pub(crate) fn normalize_one_layer(
         }
         ExprKind::BoolIf(ref b, ref e1, ref e2) => {
             match b.kind() {
-                BoolLit(true) => Ret::ValueRef(e1),
-                BoolLit(false) => Ret::ValueRef(e2),
+                Lit(Bool(true)) => Ret::ValueRef(e1),
+                Lit(Bool(false)) => Ret::ValueRef(e2),
                 _ => {
                     match (e1.kind(), e2.kind()) {
                         // Simplify `if b then True else False`
-                        (BoolLit(true), BoolLit(false)) => Ret::ValueRef(b),
+                        (Lit(Bool(true)), Lit(Bool(false))) => Ret::ValueRef(b),
                         _ if e1 == e2 => Ret::ValueRef(e1),
                         _ => Ret::Expr(expr),
                     }
diff --git a/dhall/src/semantics/nze/value.rs b/dhall/src/semantics/nze/value.rs
index 0df3c74..2ae6852 100644
--- a/dhall/src/semantics/nze/value.rs
+++ b/dhall/src/semantics/nze/value.rs
@@ -9,8 +9,8 @@ use crate::semantics::{
     TyExpr, VarEnv,
 };
 use crate::syntax::{
-    BinOp, Builtin, Const, ExprKind, Integer, InterpolatedTextContents, Label,
-    NaiveDouble, Natural, Span,
+    BinOp, Builtin, Const, ExprKind, InterpolatedTextContents, Label, LitKind,
+    Span,
 };
 use crate::{NormalizedExpr, ToExprOptions};
 
@@ -76,10 +76,7 @@ pub(crate) enum ValueKind {
 
     Var(NzVar),
     Const(Const),
-    BoolLit(bool),
-    NaturalLit(Natural),
-    IntegerLit(Integer),
-    DoubleLit(NaiveDouble),
+    Lit(LitKind),
     EmptyOptionalLit(Value),
     NEOptionalLit(Value),
     // EmptyListLit(t) means `[] : List t`, not `[] : t`
@@ -205,10 +202,7 @@ impl Value {
                     closure.to_hir(venv),
                 ),
                 ValueKind::Const(c) => ExprKind::Const(*c),
-                ValueKind::BoolLit(b) => ExprKind::BoolLit(*b),
-                ValueKind::NaturalLit(n) => ExprKind::NaturalLit(*n),
-                ValueKind::IntegerLit(n) => ExprKind::IntegerLit(*n),
-                ValueKind::DoubleLit(n) => ExprKind::DoubleLit(*n),
+                ValueKind::Lit(l) => ExprKind::Lit(l.clone()),
                 ValueKind::EmptyOptionalLit(n) => ExprKind::App(
                     Value::from_builtin(Builtin::OptionalNone).to_hir(venv),
                     n.to_hir(venv),
@@ -317,12 +311,7 @@ impl ValueKind {
 
     pub(crate) fn normalize(&self) {
         match self {
-            ValueKind::Var(..)
-            | ValueKind::Const(_)
-            | ValueKind::BoolLit(_)
-            | ValueKind::NaturalLit(_)
-            | ValueKind::IntegerLit(_)
-            | ValueKind::DoubleLit(_) => {}
+            ValueKind::Var(..) | ValueKind::Const(_) | ValueKind::Lit(_) => {}
 
             ValueKind::EmptyOptionalLit(tth) | ValueKind::EmptyListLit(tth) => {
                 tth.normalize();
diff --git a/dhall/src/semantics/tck/typecheck.rs b/dhall/src/semantics/tck/typecheck.rs
index f9ff3d3..c52cfda 100644
--- a/dhall/src/semantics/tck/typecheck.rs
+++ b/dhall/src/semantics/tck/typecheck.rs
@@ -9,7 +9,7 @@ use crate::semantics::{
     TyExpr, TyExprKind, Type, Value, ValueKind,
 };
 use crate::syntax::{
-    BinOp, Builtin, Const, ExprKind, InterpolatedTextContents, Span,
+    BinOp, Builtin, Const, ExprKind, InterpolatedTextContents, LitKind, Span,
 };
 
 fn type_of_recordtype<'a>(
@@ -115,10 +115,16 @@ fn type_one_layer(
             let t_tyexpr = typecheck(&t_hir)?;
             t_tyexpr.eval(env)
         }
-        ExprKind::BoolLit(_) => Value::from_builtin(Builtin::Bool),
-        ExprKind::NaturalLit(_) => Value::from_builtin(Builtin::Natural),
-        ExprKind::IntegerLit(_) => Value::from_builtin(Builtin::Integer),
-        ExprKind::DoubleLit(_) => Value::from_builtin(Builtin::Double),
+        ExprKind::Lit(LitKind::Bool(_)) => Value::from_builtin(Builtin::Bool),
+        ExprKind::Lit(LitKind::Natural(_)) => {
+            Value::from_builtin(Builtin::Natural)
+        }
+        ExprKind::Lit(LitKind::Integer(_)) => {
+            Value::from_builtin(Builtin::Integer)
+        }
+        ExprKind::Lit(LitKind::Double(_)) => {
+            Value::from_builtin(Builtin::Double)
+        }
         ExprKind::TextLit(interpolated) => {
             let text_type = Value::from_builtin(Builtin::Text);
             for contents in interpolated.iter() {
diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 512010a..18ec9fd 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -103,6 +103,19 @@ pub struct Expr {
 
 pub type UnspannedExpr = ExprKind<Expr>;
 
+/// Simple literals
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum LitKind {
+    ///  `True`
+    Bool(bool),
+    ///  `1`
+    Natural(Natural),
+    ///  `+2`
+    Integer(Integer),
+    ///  `3.24`
+    Double(Double),
+}
+
 /// Syntax tree for expressions
 // Having the recursion out of the enum definition enables writing
 // much more generic code and improves pattern-matching behind
@@ -110,6 +123,7 @@ pub type UnspannedExpr = ExprKind<Expr>;
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum ExprKind<SubExpr> {
     Const(Const),
+    Lit(LitKind),
     ///  `x`
     ///  `x@n`
     Var(V),
@@ -131,16 +145,8 @@ pub enum ExprKind<SubExpr> {
     Builtin(Builtin),
     // Binary operations
     BinOp(BinOp, SubExpr, SubExpr),
-    ///  `True`
-    BoolLit(bool),
     ///  `if x then y else z`
     BoolIf(SubExpr, SubExpr, SubExpr),
-    ///  `1`
-    NaturalLit(Natural),
-    ///  `+2`
-    IntegerLit(Integer),
-    ///  `3.24`
-    DoubleLit(Double),
     ///  `"Some ${interpolated} text"`
     TextLit(InterpolatedText<SubExpr>),
     ///  `[] : t`
diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
index 39959ac..c361bc1 100644
--- a/dhall/src/syntax/ast/visitor.rs
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -91,10 +91,7 @@ where
         Annot(x, t) => Annot(expr!(x)?, expr!(t)?),
         Const(k) => Const(*k),
         Builtin(v) => Builtin(*v),
-        BoolLit(b) => BoolLit(*b),
-        NaturalLit(n) => NaturalLit(*n),
-        IntegerLit(n) => IntegerLit(*n),
-        DoubleLit(n) => DoubleLit(*n),
+        Lit(l) => Lit(l.clone()),
         TextLit(t) => TextLit(t.traverse_ref(|e| expr!(e))?),
         BinOp(o, x, y) => BinOp(*o, expr!(x)?, expr!(y)?),
         BoolIf(b, t, f) => BoolIf(expr!(b)?, expr!(t)?, expr!(f)?),
diff --git a/dhall/src/syntax/binary/decode.rs b/dhall/src/syntax/binary/decode.rs
index 6fbcc10..2e50d61 100644
--- a/dhall/src/syntax/binary/decode.rs
+++ b/dhall/src/syntax/binary/decode.rs
@@ -6,8 +6,8 @@ use crate::error::DecodeError;
 use crate::syntax;
 use crate::syntax::{
     Expr, ExprKind, FilePath, FilePrefix, Hash, ImportLocation, ImportMode,
-    Integer, InterpolatedText, Label, Natural, Scheme, Span, UnspannedExpr,
-    URL, V,
+    Integer, InterpolatedText, Label, LitKind, Natural, Scheme, Span,
+    UnspannedExpr, URL, V,
 };
 use crate::DecodedExpr;
 
@@ -31,8 +31,8 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
         String(s) => match Builtin::parse(s) {
             Some(b) => ExprKind::Builtin(b),
             None => match s.as_str() {
-                "True" => BoolLit(true),
-                "False" => BoolLit(false),
+                "True" => Lit(LitKind::Bool(true)),
+                "False" => Lit(LitKind::Bool(false)),
                 "Type" => Const(Const::Type),
                 "Kind" => Const(Const::Kind),
                 "Sort" => Const(Const::Sort),
@@ -40,8 +40,8 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
             },
         },
         U64(n) => Var(V(Label::from("_"), *n as usize)),
-        F64(x) => DoubleLit((*x).into()),
-        Bool(b) => BoolLit(*b),
+        F64(x) => Lit(LitKind::Double((*x).into())),
+        Bool(b) => Lit(LitKind::Bool(*b)),
         Array(vec) => match vec.as_slice() {
             [String(l), U64(n)] => {
                 if l.as_str() == "_" {
@@ -216,9 +216,9 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                 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(15), U64(x)] => Lit(LitKind::Natural(*x as Natural)),
+            [U64(16), U64(x)] => Lit(LitKind::Integer(*x as Integer)),
+            [U64(16), I64(x)] => Lit(LitKind::Integer(*x as Integer)),
             [U64(18), String(first), rest @ ..] => {
                 TextLit(InterpolatedText::from((
                     first.clone(),
diff --git a/dhall/src/syntax/binary/encode.rs b/dhall/src/syntax/binary/encode.rs
index 686f737..291ac4a 100644
--- a/dhall/src/syntax/binary/encode.rs
+++ b/dhall/src/syntax/binary/encode.rs
@@ -46,6 +46,7 @@ where
     use std::iter::once;
     use syntax::Builtin;
     use syntax::ExprKind::*;
+    use syntax::LitKind::*;
 
     use self::Serialize::{RecordMap, UnionMap};
     fn expr(x: &Expr) -> self::Serialize<'_> {
@@ -60,10 +61,10 @@ where
     match e.as_ref() {
         Const(c) => ser.serialize_str(&c.to_string()),
         Builtin(b) => ser.serialize_str(&b.to_string()),
-        BoolLit(b) => ser.serialize_bool(*b),
-        NaturalLit(n) => ser_seq!(ser; tag(15), U64(*n as u64)),
-        IntegerLit(n) => ser_seq!(ser; tag(16), I64(*n as i64)),
-        DoubleLit(n) => {
+        Lit(Bool(b)) => ser.serialize_bool(*b),
+        Lit(Natural(n)) => ser_seq!(ser; tag(15), U64(*n as u64)),
+        Lit(Integer(n)) => ser_seq!(ser; tag(16), I64(*n as i64)),
+        Lit(Double(n)) => {
             let n: f64 = (*n).into();
             ser.serialize_f64(n)
         }
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index 0ff1363..f3ebd2b 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -7,6 +7,7 @@ use pest_consume::{match_nodes, Parser};
 
 use crate::syntax::map::{DupTreeMap, DupTreeSet};
 use crate::syntax::ExprKind::*;
+use crate::syntax::LitKind::*;
 use crate::syntax::{
     Double, Expr, FilePath, FilePrefix, Hash, ImportLocation, ImportMode,
     Integer, InterpolatedText, InterpolatedTextContents, Label, NaiveDouble,
@@ -344,8 +345,8 @@ impl DhallParser {
         let e = match crate::syntax::Builtin::parse(s) {
             Some(b) => Builtin(b),
             None => match s {
-                "True" => BoolLit(true),
-                "False" => BoolLit(false),
+                "True" => Lit(Bool(true)),
+                "False" => Lit(Bool(false)),
                 "Type" => Const(crate::syntax::Const::Type),
                 "Kind" => Const(crate::syntax::Const::Kind),
                 "Sort" => Const(crate::syntax::Const::Sort),
@@ -833,9 +834,9 @@ impl DhallParser {
     #[alias(expression, shortcut = true)]
     fn primitive_expression(input: ParseInput) -> ParseResult<Expr> {
         Ok(match_nodes!(input.children();
-            [double_literal(n)] => spanned(input, DoubleLit(n)),
-            [natural_literal(n)] => spanned(input, NaturalLit(n)),
-            [integer_literal(n)] => spanned(input, IntegerLit(n)),
+            [double_literal(n)] => spanned(input, Lit(Double(n))),
+            [natural_literal(n)] => spanned(input, Lit(Natural(n))),
+            [integer_literal(n)] => spanned(input, Lit(Integer(n))),
             [double_quote_literal(s)] => spanned(input, TextLit(s)),
             [single_quote_literal(s)] => spanned(input, TextLit(s)),
             [record_type_or_literal(e)] => spanned(input, e),
diff --git a/dhall/src/syntax/text/printer.rs b/dhall/src/syntax/text/printer.rs
index d1c9588..8891d41 100644
--- a/dhall/src/syntax/text/printer.rs
+++ b/dhall/src/syntax/text/printer.rs
@@ -196,15 +196,7 @@ impl<SE: Display + Clone> Display for ExprKind<SE> {
             Var(a) => a.fmt(f)?,
             Const(k) => k.fmt(f)?,
             Builtin(v) => v.fmt(f)?,
-            BoolLit(true) => f.write_str("True")?,
-            BoolLit(false) => f.write_str("False")?,
-            NaturalLit(a) => a.fmt(f)?,
-            IntegerLit(a) if *a >= 0 => {
-                f.write_str("+")?;
-                a.fmt(f)?;
-            }
-            IntegerLit(a) => a.fmt(f)?,
-            DoubleLit(a) => a.fmt(f)?,
+            Lit(a) => a.fmt(f)?,
             TextLit(a) => a.fmt(f)?,
             RecordType(a) if a.is_empty() => f.write_str("{}")?,
             RecordType(a) => fmt_list("{ ", ", ", " }", a, f, |(k, t), f| {
@@ -239,7 +231,25 @@ impl<SE: Display + Clone> Display for ExprKind<SE> {
 
 impl Display for Expr {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        self.as_ref().fmt_phase(f, PrintPhase::Base)
+        self.kind().fmt_phase(f, PrintPhase::Base)
+    }
+}
+
+impl Display for LitKind {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        use LitKind::*;
+        match self {
+            Bool(true) => f.write_str("True")?,
+            Bool(false) => f.write_str("False")?,
+            Natural(a) => a.fmt(f)?,
+            Integer(a) if *a >= 0 => {
+                f.write_str("+")?;
+                a.fmt(f)?;
+            }
+            Integer(a) => a.fmt(f)?,
+            Double(a) => a.fmt(f)?,
+        }
+        Ok(())
     }
 }