Define equality for boolean selectors.

lib/src/intersection_selector.dart

Index: lib/src/intersection_selector.dart
diff --git a/lib/src/intersection_selector.dart b/lib/src/intersection_selector.dart
index aa51bf94bb2d31f5cacf0fe8dbacaa8392b3f2bf..8c15254d031493798dbce4fd9fc85028370ebc7a 100644
--- a/lib/src/intersection_selector.dart
+++ b/lib/src/intersection_selector.dart
@@ -32,4 +32,11 @@ class IntersectionSelector implements BooleanSelector {
   }
 
   String toString() => "($_selector1) && ($_selector2)";
+
+  bool operator==(other) =>
+      other is IntersectionSelector &&
+      _selector1 == other._selector1 &&
+      _selector2 == other._selector2;
+
+  int get hashCode => _selector1.hashCode ^ _selector2.hashCode;
 }