From 41ed27574cf871f48d4c4ddfed5285b9853b41d3 Mon Sep 17 00:00:00 2001
From: Jim Lawson
Date: Fri, 3 Feb 2017 09:07:10 -0800
Subject: Fix potential NPE if we try to evaluate isMissingIOWrapper() inside
 IO(). (#479)

---
 chiselFrontend/src/main/scala/chisel3/core/Binding.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'chiselFrontend/src/main')

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Binding.scala b/chiselFrontend/src/main/scala/chisel3/core/Binding.scala
index 71c441a7..a857ae85 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Binding.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Binding.scala
@@ -155,7 +155,9 @@ object Binding {
             //  we know the wrapper is missing, whether or not the element is a member of io.
             //  But if it's not an io element, we want to issue the complementary "unbound" error.
             //  Revisit this when we collect error messages instead of throwing exceptions.
-            x.io.flatten.contains(element)
+            // The null test below is due to the fact that we may be evaluating the arguments
+            //  of the IO() wrapper itself.
+            (x.io != null) && x.io.flatten.contains(element)
           }
         }
       }
-- 
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