From 63aa21c581933a10b2b1ab96c632c72834cf2115 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 15 Apr 2019 12:22:02 +0200
Subject: Handle empty optionals correctly

Closes #78
---
 dhall/src/typecheck.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'dhall/src/typecheck.rs')

diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index b8f2d86..5162f4f 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -266,6 +266,9 @@ fn type_of_builtin<S>(b: Builtin) -> Expr<S, Normalized<'static>> {
             forall (nothing: optional) ->
             optional
         ),
+        OptionalNone => dhall::expr!(
+            forall (a: Type) -> Optional a
+        ),
         _ => panic!("Unimplemented typecheck case: {:?}", b),
     }
 }
@@ -544,6 +547,17 @@ fn type_last_layer(
             let t = x.get_type_move()?.into_normalized()?.into_expr();
             Ok(RetExpr(dhall::expr!(List t)))
         }
+        OldOptionalLit(None, t) => {
+            let t = t.into_expr();
+            let e = dhall::subexpr!(None t);
+            Ok(RetType(type_with(ctx, e)?.get_type()?.into_owned()))
+        }
+        OldOptionalLit(Some(x), t) => {
+            let x = x.into_expr();
+            let t = t.into_expr();
+            let e = dhall::subexpr!(Some x : Optional t);
+            Ok(RetType(type_with(ctx, e)?.get_type()?.into_owned()))
+        }
         EmptyOptionalLit(t) => {
             let t = t.normalize().into_type();
             ensure_simple_type!(
-- 
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