two empties make an empty

Author: justinbmeyer

src/types/make-maybe-test.js

@@ -183,6 +183,19 @@ QUnit.test("difference", function() {
 	);
 	QUnit.deepEqual(res, gt3, "secondary and primary");
 
+	res = set.difference(
+		new MaybeDateStringSet({
+			range: new is.In([3]),
+			enum: set.EMPTY
+		}),
+		new MaybeDateStringSet({
+			range: new is.In([3]),
+			enum: set.EMPTY
+		})
+	);
+
+	QUnit.equal(res, set.EMPTY, "equal is empty");
+
 });
 
 QUnit.test("difference with ComparisonSet", function() {
@@ -304,7 +317,23 @@ QUnit.test("union", function() {
 });
 
 
+QUnit.test("isSubset", function() {
+	var res;
 
+	res = set.isSubset(
+		new MaybeDateStringSet({
+			range: new is.In([3]),
+			enum: set.EMPTY
+		}),
+		new MaybeDateStringSet({
+			range: new is.In([3]),
+			enum: set.EMPTY
+		})
+	);
+
+	QUnit.ok(res, "is a subset");
+
+});
 
 QUnit.test("can make maybe type from normal type and makeMaybeSetType", function() {
 	var MaybeNumber = canReflect.assignSymbols({}, {

src/types/make-maybe.js

@@ -95,6 +95,9 @@ function makeMaybe(inValues, makeChildType) {
 		} else {
 			this.enum = result.enum;
 		}
+		if(this.enum === set.EMPTY && this.range === set.EMPTY) {
+			return set.EMPTY;
+		}
 	}
 	Maybe.prototype.orValues = function() {
 		var values = [];
@@ -112,6 +115,8 @@ function makeMaybe(inValues, makeChildType) {
 		return rangeIsMember.apply(this.range, arguments) || enumIsMember.apply(this.enum, arguments);
 	}
 
+
+
 	set.defineComparison(Maybe, Maybe, {
 		union: function(maybeA, maybeB) {
 			var enumSet = set.union(maybeA.enum, maybeB.enum);