Introduce @flatten annotation

upickle/implicits/src-2/upickle/implicits/MacroImplicits.scala

@@ -43,7 +43,7 @@ trait MacroImplicits extends MacrosCommon { this: upickle.core.Types =>
   def macroW[T]: Writer[T] = macro MacroImplicits.applyW[T]
   def macroRW[T]: ReadWriter[T] = macro MacroImplicits.applyRW[ReadWriter[T]]
 
-  def macroR0[T, M[_]]: Reader[T] = macro internal.Macros.macroRImpl[T, M]
-  def macroW0[T, M[_]]: Writer[T] = macro internal.Macros.macroWImpl[T, M]
+  def macroR0[T, M[_]]: Reader[T] = macro internal.Macros2.macroRImpl[T, M]
+  def macroW0[T, M[_]]: Writer[T] = macro internal.Macros2.macroWImpl[T, M]
 }
 

upickle/implicits/src-2/upickle/implicits/internal/Macros.scala

@@ -10,6 +10,11 @@ import upickle.implicits.{MacrosCommon, key}
 import language.higherKinds
 import language.existentials
 
+/**
+ * This file is deprecated and remained here for binary compatibility.
+ * Please use upickle/implicits/src-2/upickle/implicits/internal/Macros2.scala instead.
+ */
+
 /**
  * Implementation of macros used by uPickle to serialize and deserialize
  * case classes automatically. You probably shouldn't need to use these
@@ -466,6 +471,8 @@ object Macros {
       q"${c.prefix}.Writer.merge[$targetType](..$subtree)"
     }
   }
+
+  @deprecated("Use Macros2 instead")
   def macroRImpl[T, R[_]](c0: scala.reflect.macros.blackbox.Context)
                          (implicit e1: c0.WeakTypeTag[T], e2: c0.WeakTypeTag[R[_]]): c0.Expr[R[T]] = {
     import c0.universe._
@@ -477,6 +484,7 @@ object Macros {
     c0.Expr[R[T]](res)
   }
 
+  @deprecated("Use Macros2 instead")
   def macroWImpl[T, W[_]](c0: scala.reflect.macros.blackbox.Context)
                          (implicit e1: c0.WeakTypeTag[T], e2: c0.WeakTypeTag[W[_]]): c0.Expr[W[T]] = {
     import c0.universe._