Fix TypeApplications.appliedTo instantiating classes.

self can be a TermRef to a constructor created by tpd.New.
It used to work before last reiteration of hk-types.

Author: DarkDimius

src/dotty/tools/dotc/core/TypeApplications.scala

@@ -480,13 +480,12 @@ class TypeApplications(val self: Type) extends AnyVal {
       }
     }
     if (args.isEmpty || ctx.erasedTypes) self
+    else if (self.widen.isInstanceOf[PolyType]) self.widen.asInstanceOf[PolyType].instantiate(args)
     else self.stripTypeVar match {
       case EtaExpansion(self1) =>
         self1.appliedTo(args)
       case TypeLambda(_, _, body) if !args.exists(_.isInstanceOf[TypeBounds]) =>
         substHkArgs(body)
-      case self: PolyType =>
-        self.instantiate(args)
       case _ =>
         appliedTo(args, typeParams)
     }