Handle nullary union variants

Closes #36

3 files changed, 14 insertions, 7 deletions

diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index fa669d8..7f56669 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -667,12 +667,12 @@ mod spec_tests {
     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_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_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_UnionTypeNormalizeArguments, "unit/UnionTypeNormalizeArguments");
     norm!(success_unit_Variable, "unit/Variable");
 }
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index d9566d0..ffa149b 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -1021,7 +1021,7 @@ mod spec_tests {
     // 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_success!(tc_success_simple_unionsOfTypes, "simple/unionsOfTypes");
 
     // tc_failure!(tc_failure_combineMixedRecords, "combineMixedRecords");
     // tc_failure!(tc_failure_duplicateFields, "duplicateFields");
diff --git a/dhall_core/src/parser.rs b/dhall_core/src/parser.rs
index a335ccc..b463073 100644
--- a/dhall_core/src/parser.rs
+++ b/dhall_core/src/parser.rs
@@ -895,7 +895,8 @@ make_parser! {
     ));
 
     rule!(union_type_entry<(Label, Option<ParsedSubExpr<'a>>)>; children!(
-        [label(name), expression(expr)] => (name, Option::Some(rc(expr)))
+        [label(name), expression(expr)] => (name, Option::Some(rc(expr))),
+        [label(name)] => (name, Option::None),
     ));
 
     // TODO: unary union variants
@@ -910,6 +911,12 @@ make_parser! {
         [expression(e)] => {
             (Option::Some(rc(e)), (Option::None, BTreeMap::new()))
         },
+        [non_empty_union_type_or_literal(rest)] => {
+            (Option::None, rest)
+        },
+        [] => {
+            (Option::None, (Option::None, BTreeMap::new()))
+        },
     ));
 
     rule!(non_empty_list_literal<ParsedExpr<'a>> as expression; span;