Refactor decorateTypeApplication as implicit class

Author: OlivierBlanvillain

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

@@ -154,10 +154,11 @@ object TypeApplications {
   }
 }
 
-import TypeApplications._
-
 /** A decorator that provides methods for modeling type application */
-class TypeApplications(val self: Type) extends AnyVal {
+trait TypeApplications extends Any {
+  def self: Type
+
+  import TypeApplications._
 
   /** The type parameters of this type are:
    *  For a ClassInfo type, the type parameters of its class.

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -4560,12 +4560,12 @@ object Types {
   }
 
   // ----- Decorator implicits --------------------------------------------
-
-  implicit def decorateTypeApplications(tpe: Type): TypeApplications = new TypeApplications(tpe)
+  implicit class TypeApplicationsypyp(val self: Type) extends AnyVal with TypeApplications
 
   implicit class typeListDeco(val tps1: List[Type]) extends AnyVal {
     @tailrec def stableHash: Boolean =
       tps1.isEmpty || tps1.head.stableHash && tps1.tail.stableHash
+
     @tailrec def equalElements(tps2: List[Type], bs: BinderPairs): Boolean =
       (tps1 `eq` tps2) || {
         if (tps1.isEmpty) tps2.isEmpty