Add quoted.Type.apply

This is intended as a stub. Calls to this method will be replaced
by implicit type tag searches.

Also, rework definition of quote and splice methods. This could also
have contributed in the slowdown we were seeing in #3721.

Author: odersky

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

@@ -609,14 +609,20 @@ class Definitions {
   lazy val QuotedExprType = ctx.requiredClassRef("scala.quoted.Expr")
   def QuotedExprClass(implicit ctx: Context) = QuotedExprType.symbol.asClass
 
-    def QuotedExpr_~(implicit ctx: Context) = QuotedExprClass.requiredMethod(nme.UNARY_~)
-    def QuotedExpr_run(implicit ctx: Context) = QuotedExprClass.requiredMethod(nme.run)
+    lazy val QuotedExpr_spliceR = QuotedExprClass.requiredMethod(nme.UNARY_~)
+    def QuotedExpr_~(implicit ctx: Context) = QuotedExpr_spliceR.symbol
+    lazy val QuotedExpr_runR = QuotedExprClass.requiredMethodRef(nme.run)
+    def QuotedExpr_run(implicit ctx: Context) = QuotedExpr_runR.symbol
 
   lazy val QuotedTypeType = ctx.requiredClassRef("scala.quoted.Type")
   def QuotedTypeClass(implicit ctx: Context) = QuotedTypeType.symbol.asClass
 
-    def QuotedType_~(implicit ctx: Context) =
-      QuotedTypeClass.info.member(tpnme.UNARY_~).symbol.asType
+    lazy val QuotedType_spliceR = QuotedTypeClass.requiredType(tpnme.UNARY_~).typeRef
+    def QuotedType_~ = QuotedType_spliceR.symbol
+
+  lazy val QuotedTypeModule = QuotedTypeClass.companionModule
+    lazy val QuotedType_applyR = QuotedTypeModule.requiredMethodRef(nme.apply)
+    def QuotedType_apply(implicit ctx: Context) = QuotedType_applyR.symbol
 
   def Unpickler_unpickleExpr = ctx.requiredMethod("scala.runtime.quoted.Unpickler.unpickleExpr")
   def Unpickler_unpickleType = ctx.requiredMethod("scala.runtime.quoted.Unpickler.unpickleType")

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

@@ -313,6 +313,9 @@ object Denotations {
     def requiredClass(name: PreName)(implicit ctx: Context): ClassSymbol =
       info.member(name.toTypeName).requiredSymbol(_.isClass).asClass
 
+    def requiredType(name: PreName)(implicit ctx: Context): TypeSymbol =
+      info.member(name.toTypeName).requiredSymbol(_.isType).asType
+
     /** The alternative of this denotation that has a type matching `targetType` when seen
      *  as a member of type `site`, `NoDenotation` if none exists.
      */

compiler/src/dotty/tools/dotc/transform/ReifyQuotes.scala

@@ -22,7 +22,7 @@ import dotty.tools.dotc.core.quoted._
 /** Translates quoted terms and types to `unpickle` method calls.
  *  Checks that the phase consistency principle (PCP) holds.
  */
-class ReifyQuotes extends MacroTransform {
+class ReifyQuotes extends MacroTransformWithImplicits {
   import ast.tpd._
 
   override def phaseName: String = "reifyQuotes"

library/src/scala/quoted/Type.scala

@@ -9,6 +9,8 @@ abstract class Type[T] extends Quoted {
 /** Some basic type tags, currently incomplete */
 object Type {
 
+  implicit def apply[T]: Type[T] = ???
+
   class TaggedPrimitive[T] private[Type] (implicit val ct: ClassTag[T]) extends Type[T]
 
   implicit def UnitTag: Type[Unit] = new TaggedPrimitive[Unit]