Erasure casting should perform primitive conversions

After erasure, asInstanceworks only bedtween reference types, so erasure
is not allowed to insert asInstanceOfs between numeric types. Previously
this made t1260 fail even if LambdaLift is disabled.

Author: odersky

src/dotty/tools/dotc/transform/Erasure.scala

@@ -195,8 +195,8 @@ object Erasure extends TypeTestsCasts{
           // See SI-2386 for one example of when this might be necessary.
           cast(ref(defn.runtimeMethod(nme.toObjectArray)).appliedTo(tree), pt)
         case _ =>
-          ctx.log(s"casting from ${tree.showSummary}: ${tree.tpe.show} to ${pt.show}")
-          tree.asInstance(pt)
+          if (pt.isPrimitiveValueType) primitiveConversion(tree, pt.classSymbol)
+          else tree.asInstance(pt)
       }
     }