From 83bc67d4572fe7961842f915d5559ee489e13dfd Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Sat, 20 Apr 2019 23:12:25 +0200
Subject: An empty optional value is purely semantic

---
 dhall/src/binary.rs    |  2 +-
 dhall/src/normalize.rs | 13 +++++--------
 dhall/src/typecheck.rs |  8 +-------
 3 files changed, 7 insertions(+), 16 deletions(-)

(limited to 'dhall')

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,
-- 
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