From c0918c69e578edad40320e0a5bac1603f5ce94fa Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 19 Jul 2015 13:05:56 +0200
Subject: Better error reporting in TreePickler

Turn a possible NPE into an AssertionError. The latter
are caught in pickleTree, so an error leaves a trace about
what was pickled.
---
 src/dotty/tools/dotc/core/tasty/TreePickler.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/dotty/tools/dotc/core/tasty/TreePickler.scala b/src/dotty/tools/dotc/core/tasty/TreePickler.scala
index 8847d2de3..a23d59339 100644
--- a/src/dotty/tools/dotc/core/tasty/TreePickler.scala
+++ b/src/dotty/tools/dotc/core/tasty/TreePickler.scala
@@ -200,7 +200,9 @@ class TreePickler(pickler: TastyPickler) {
         withLength { pickleType(tpe.thistpe); pickleType(tpe.supertpe)}
       case tpe: RefinedThis =>
         writeByte(REFINEDthis)
-        writeRef(pickledTypes.get(tpe.binder).asInstanceOf[Addr])
+        val binderAddr = pickledTypes.get(tpe.binder)
+        assert(binderAddr != null)
+        writeRef(binderAddr.asInstanceOf[Addr])
       case tpe: SkolemType =>
         pickleType(tpe.info)
       case tpe: RefinedType =>
-- 
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