SI-7015 Cleanup from review of null duplication

Based on feedback on https://github.com/scala/scala/pull/2147

* Assertion in GenICode#adaptNullRef reports the erroneous type
* Test makes the Null type explicit for greater clarity

1 files changed, 1 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index 439bb74267..7e17495035 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -1025,7 +1025,7 @@ abstract class GenICode extends SubComponent  {
       // this value into a local of type Null and we want the JVM to see that it's
       // a null value so we don't have to also adapt local loads.
       if (from == NullReference && to != UNIT && to != ObjectReference && to != AnyRefReference) {
-        assert(to.isReferenceType, "Attempt to adapt a null to a non reference type")
+        assert(to.isReferenceType, "Attempt to adapt a null to a non reference type $to.")
         // adapt by dropping what we've got and pushing a null which
         // will convince the JVM we really do have null
         ctx.bb.emit(DROP(from), pos)