An empty optional value is purely semantic

8 files changed, 15 insertions, 35 deletions

diff --git a/dhall/src/binary.rs b/dhall/src/binary.rs
index 62ebcf7..7ded3a5 100644
--- a/dhall/src/binary.rs
+++ b/dhall/src/binary.rs
@@ -111,7 +111,7 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
             }
             [U64(5), Null, x] => {
                 let x = cbor_value_to_dhall(&x)?;
-                NEOptionalLit(x)
+                SomeLit(x)
             }
             [U64(5), t, x] => {
                 let x = cbor_value_to_dhall(&x)?;
diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index 9e7c531..f092c4d 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -366,10 +366,12 @@ impl WHNF {
             WHNF::NaturalLit(n) => rc(ExprF::NaturalLit(n)),
             WHNF::IntegerLit(n) => rc(ExprF::IntegerLit(n)),
             WHNF::EmptyOptionalLit(n) => {
-                rc(ExprF::EmptyOptionalLit(n.normalize().normalize_to_expr()))
+                WHNF::Expr(rc(ExprF::Builtin(Builtin::OptionalNone)))
+                    .app(n.normalize())
+                    .normalize_to_expr()
             }
             WHNF::NEOptionalLit(n) => {
-                rc(ExprF::NEOptionalLit(n.normalize().normalize_to_expr()))
+                rc(ExprF::SomeLit(n.normalize().normalize_to_expr()))
             }
             WHNF::EmptyListLit(n) => {
                 rc(ExprF::EmptyListLit(n.normalize().normalize_to_expr()))
@@ -628,12 +630,7 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> WHNF {
         ExprF::OldOptionalLit(Some(e), _) => {
             WHNF::NEOptionalLit(Now::new(ctx, e.clone()))
         }
-        ExprF::EmptyOptionalLit(e) => {
-            WHNF::EmptyOptionalLit(Now::new(ctx, e.clone()))
-        }
-        ExprF::NEOptionalLit(e) => {
-            WHNF::NEOptionalLit(Now::new(ctx, e.clone()))
-        }
+        ExprF::SomeLit(e) => WHNF::NEOptionalLit(Now::new(ctx, e.clone())),
         ExprF::EmptyListLit(e) => WHNF::EmptyListLit(Now::new(ctx, e.clone())),
         ExprF::NEListLit(elts) => WHNF::NEListLit(
             elts.iter()
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index ddb96da..b26f845 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -563,13 +563,7 @@ fn type_last_layer(
             let e = dhall::subexpr!(Some x : Optional t);
             Ok(RetType(type_with(ctx, e)?.get_type()?.into_owned()))
         }
-        EmptyOptionalLit(t) => {
-            let t = t.normalize();
-            ensure_simple_type!(t, mkerr(InvalidOptionalType(t)));
-            let t = t.embed();
-            Ok(RetExpr(dhall::expr!(Optional t)))
-        }
-        NEOptionalLit(x) => {
+        SomeLit(x) => {
             let tx = x.get_type_move()?;
             ensure_simple_type!(
                 tx,
diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index 9a8acc2..fa6fca4 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -180,10 +180,8 @@ pub enum ExprF<SubExpr, Label, Note, Embed> {
     ///  `[] : Optional a`
     ///  `[x] : Optional a`
     OldOptionalLit(Option<SubExpr>, SubExpr),
-    ///  `None t`
-    EmptyOptionalLit(SubExpr),
     ///  `Some e`
-    NEOptionalLit(SubExpr),
+    SomeLit(SubExpr),
     ///  `{ k1 : t1, k2 : t1 }`
     RecordType(BTreeMap<Label, SubExpr>),
     ///  `{ k1 = v1, k2 = v2 }`
diff --git a/dhall_core/src/parser.rs b/dhall_core/src/parser.rs
index 31249a9..ba15bae 100644
--- a/dhall_core/src/parser.rs
+++ b/dhall_core/src/parser.rs
@@ -754,7 +754,7 @@ make_parser! {
             children!(
         [expression(e)] => e,
         [Some_(()), expression(e)] => {
-            spanned(span, NEOptionalLit(rc(e)))
+            spanned(span, SomeLit(rc(e)))
         },
         [merge(()), expression(x), expression(y)] => {
             spanned(span, Merge(rc(x), rc(y), None))
diff --git a/dhall_core/src/printer.rs b/dhall_core/src/printer.rs
index ea291a9..c4bad71 100644
--- a/dhall_core/src/printer.rs
+++ b/dhall_core/src/printer.rs
@@ -38,10 +38,7 @@ impl<SE: Display + Clone, N, E: Display> Display for ExprF<SE, Label, N, E> {
             OldOptionalLit(Some(x), t) => {
                 write!(f, "[{}] : Optional {}", x, t)?;
             }
-            EmptyOptionalLit(t) => {
-                write!(f, "None {}", t)?;
-            }
-            NEOptionalLit(e) => {
+            SomeLit(e) => {
                 write!(f, "Some {}", e)?;
             }
             Merge(a, b, c) => {
@@ -159,8 +156,7 @@ impl<S: Clone, A: Display + Clone> Expr<S, A> {
             | EmptyListLit(_)
             | NEListLit(_)
             | OldOptionalLit(_, _)
-            | EmptyOptionalLit(_)
-            | NEOptionalLit(_)
+            | SomeLit(_)
             | Merge(_, _, _)
             | Annot(_, _)
                 if phase > Base =>
@@ -200,8 +196,7 @@ impl<S: Clone, A: Display + Clone> Expr<S, A> {
             ),
             EmptyListLit(t) => EmptyListLit(t.phase(Import)),
             OldOptionalLit(x, t) => OldOptionalLit(x, t.phase(Import)),
-            EmptyOptionalLit(t) => EmptyOptionalLit(t.phase(Import)),
-            NEOptionalLit(e) => NEOptionalLit(e.phase(Import)),
+            SomeLit(e) => SomeLit(e.phase(Import)),
             ExprF::App(f, a) => ExprF::App(f.phase(Import), a.phase(Import)),
             Field(a, b) => Field(a.phase(Primitive), b),
             Projection(e, ls) => Projection(e.phase(Primitive), ls),
diff --git a/dhall_core/src/visitor.rs b/dhall_core/src/visitor.rs
index c15aacd..caaefce 100644
--- a/dhall_core/src/visitor.rs
+++ b/dhall_core/src/visitor.rs
@@ -153,8 +153,7 @@ where
                 opt(x, |e| v.visit_subexpr(e))?,
                 v.visit_subexpr(t)?,
             ),
-            EmptyOptionalLit(t) => EmptyOptionalLit(v.visit_subexpr(t)?),
-            NEOptionalLit(e) => NEOptionalLit(v.visit_subexpr(e)?),
+            SomeLit(e) => SomeLit(v.visit_subexpr(e)?),
             RecordType(kts) => RecordType(btmap(kts, v)?),
             RecordLit(kvs) => RecordLit(btmap(kvs, v)?),
             UnionType(kts) => UnionType(btoptmap(kts, v)?),
diff --git a/dhall_generator/src/quote.rs b/dhall_generator/src/quote.rs
index 38910a8..c588eda 100644
--- a/dhall_generator/src/quote.rs
+++ b/dhall_generator/src/quote.rs
@@ -66,11 +66,8 @@ where
         BoolLit(b) => {
             quote! { dhall_core::ExprF::BoolLit(#b) }
         }
-        EmptyOptionalLit(x) => {
-            quote! { dhall_core::ExprF::EmptyOptionalLit(#x) }
-        }
-        NEOptionalLit(x) => {
-            quote! { dhall_core::ExprF::NEOptionalLit(#x) }
+        SomeLit(x) => {
+            quote! { dhall_core::ExprF::SomeLit(#x) }
         }
         EmptyListLit(t) => {
             quote! { dhall_core::ExprF::EmptyListLit(#t) }