From 9c923fe98a46a1d703a6f02a5606651f9f0f2ab5 Mon Sep 17 00:00:00 2001
From: Natalie Weizenbaum <nex342@gmail.com>
Date: Fri, 21 Oct 2016 21:56:27 -0700
Subject: [PATCH] Support guarded variables.

---
 lib/src/visitor/perform.dart | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/src/visitor/perform.dart b/lib/src/visitor/perform.dart
index 32fe9487..87162cb6 100644
--- a/lib/src/visitor/perform.dart
+++ b/lib/src/visitor/perform.dart
@@ -723,6 +723,11 @@ class _PerformVisitor
   }
 
   Value visitVariableDeclaration(VariableDeclaration node) {
+    if (node.isGuarded) {
+      var value = _environment.getVariable(node.name);
+      if (value != null && value != sassNull) return;
+    }
+
     _environment.setVariable(
         node.name, node.expression.accept(this).withoutSlash(),
         global: node.isGlobal);