Fix expansion of SuperRef

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/init/Checking.scala

@@ -416,8 +416,8 @@ object Checking {
       case _: ThisRef | _: Fun | _: Warm | _: Cold =>
         Set(pot)
 
-      case _: SuperRef =>
-        throw new Exception("Unexpected SuperRef")
+      case SuperRef(pot1, supercls) =>
+        expand(pot1).map { SuperRef(_, supercls)(pot.source) }
     }
   }
 }

compiler/src/dotty/tools/dotc/transform/init/Summarization.scala

@@ -32,7 +32,7 @@ object Summarization {
 
       case supert: Super =>
         val SuperType(thisTp, superTp) = supert.tpe.asInstanceOf[SuperType]
-        val thisRef = ThisRef(thisTp.classSymbol.asClass)(supert)
+        val thisRef = ThisRef(thisTp.widen.classSymbol.asClass)(supert)
         val pot = SuperRef(thisRef, superTp.classSymbol.asClass)(supert)
         Summary.empty + pot