Switch TypeApplications to given extensions

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

@@ -13,16 +13,10 @@ import StdNames.nme
 import Flags.{Module, Provisional}
 import dotty.tools.dotc.config.Config
 
-object TypeApplications {
+object TypeApplications:
 
   type TypeParamInfo = ParamInfo.Of[TypeName]
 
-  /** Assert type is not a TypeBounds instance and return it unchanged */
-  def noBounds(tp: Type): Type = tp match {
-    case tp: TypeBounds => throw new AssertionError("no TypeBounds allowed")
-    case _ => tp
-  }
-
   /** Extractor for
    *
    *    [X1: B1, ..., Xn: Bn] -> C[X1, ..., Xn]
@@ -153,13 +147,13 @@ object TypeApplications {
         mapOver(t)
     }
   }
-}
-
-import TypeApplications.*
 
-/** A decorator that provides methods for modeling type application */
-class TypeApplications(val self: Type) extends AnyVal {
+/** Extensions that model type application.
+ */
+trait TypeApplications:
+  import TypeApplications.*
 
+  extension (self: Type) { // braces to avoid indent
   /** The type parameters of this type are:
    *  For a ClassInfo type, the type parameters of its class.
    *  For a typeref referring to a class, the type parameters of the class.
@@ -554,7 +548,7 @@ class TypeApplications(val self: Type) extends AnyVal {
     case _ => self.dropDependentRefinement.dealias.argInfos
 
   /** Argument types where existential types in arguments are disallowed */
-  def argTypes(using Context): List[Type] = argInfos mapConserve noBounds
+  def argTypes(using Context): List[Type] = argInfos.mapConserve(_.noBounds)
 
   /** Argument types where existential types in arguments are approximated by their lower bound */
   def argTypesLo(using Context): List[Type] = argInfos.mapConserve(_.loBound)
@@ -588,4 +582,9 @@ class TypeApplications(val self: Type) extends AnyVal {
       .orElse(self.baseType(defn.ArrayClass))
       .argInfos.headOption.getOrElse(NoType)
   }
-}
+
+  /** Assert type is not a TypeBounds instance and return it unchanged */
+  def noBounds: self.type =
+    assert(!self.isInstanceOf[TypeBounds], "no TypeBounds allowed")
+    self
+  }

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

@@ -2132,6 +2132,9 @@ object Types extends TypeUtils {
     /** Is the `hash` of this type the same for all possible sequences of enclosing binders? */
     def hashIsStable: Boolean = true
   }
+  object Type:
+    // Extensions that model type application.
+    given TypeApplications()
 
   // end Type
 
@@ -7160,8 +7163,6 @@ object Types extends TypeUtils {
 
   // ----- Helpers and Decorator implicits --------------------------------------
 
-  implicit def decorateTypeApplications(tpe: Type): TypeApplications = new TypeApplications(tpe)
-
   extension (tps1: List[Type]) {
     @tailrec def hashIsStable: Boolean =
       tps1.isEmpty || tps1.head.hashIsStable && tps1.tail.hashIsStable

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -1897,9 +1897,9 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
           dotc.core.Symbols.defn.isTupleNType(self)
         def select(sym: Symbol): TypeRepr = self.select(sym)
         def appliedTo(targ: TypeRepr): TypeRepr =
-          dotc.core.Types.decorateTypeApplications(self).appliedTo(targ)
+          Types.Type.given_TypeApplications.appliedTo(self)(targ)
         def appliedTo(targs: List[TypeRepr]): TypeRepr =
-          dotc.core.Types.decorateTypeApplications(self).appliedTo(targs)
+          Types.Type.given_TypeApplications.appliedTo(self)(targs)
         def substituteTypes(from: List[Symbol], to: List[TypeRepr]): TypeRepr =
           self.subst(from, to)