Polymorphic macro bundle fails when compiled by Scala 3.0.0-RC1

[bishabosha]

reproduction steps

using Scala 2.13.5,

Compile with Scala 3.0.0-RC1:

// TpeTag.scala
package testframework

final case class TpeTag[T](repr: String)

// package.scala
package object testframework {

  import scala.language.experimental.macros

  implicit def mkTpeTag[T]: TpeTag[T] = macro TpeTagImpl.mkTag[T]

  inline given mkTpeTag[T]: TpeTag[T] = ${ ??? } // unused placeholder to satisfy compiler
}

// TpeTagImpl.scala
package testframework

// using "org.scala-lang" % "scala-reflect" % "2.13.5"

import scala.reflect.macros.blackbox.Context

class TpeTagImpl(val c: Context) {
  import c.universe._

  def mkTag[T](implicit T: c.WeakTypeTag[T]): Tree = {
    val tpeString = Literal(Constant(T.tpe.toString))
    val tpeTagCls = c.mirror.staticClass(classOf[testframework.TpeTag[_]].getName())
    val tpeTagOfT = appliedType(tpeTagCls.toType, T.tpe)
    New(tpeTagOfT, tpeString) // new testframework.TpeTag[T](T.tpe.toString)
  }

}

Compile with Scala 2.13.5:

// Main.scala
import testframework._

object Main extends App {
  println(implicitly[TpeTag[List[String]]])
}

problem

When I compile Main.scala using sbt and scala sandwich I get the error, presumably linked to reflective invocation of the macro:

[error] Main.scala:6:21: exception during macro expansion: testframework / Compile / compileIncremental 0s
[error] java.lang.IllegalArgumentException: wrong number of arguments
[error]   println(implicitly[TpeTag[List[String]]])
[error]                     ^
[error] one error found

This error goes away if I rewrite TpeTagImpl.mkTag as a standard macro and not a bundle, or if I compile the bundle with Scala 2.13.5. I can't see a difference in the bytecode except the scala 3 version is missing some inserted checkcast instructions before calling ScalaRunTime.wrapRefArray, also the tasty for testframework.mkTpeTag is the same when the bundle is compiled by either Scala version.

Also, there is no failure for a bundle which is not polymorphic.

[dwijnand]

also the tasty for testframework.mkTpeTag is the same when the bundle is compiled by either Scala version

Not sure what you mean there, as there is no tasty when compiling with 2.13.4.

I'm assuming that this is a tastyreader bug, that is, something that you need to be reading out of the tasty such that the compiler wires things correctly?

Btw I'd avoid nesting things in the package object, as classes in package objects are hazardous/buggy and thus discouraged.

[bishabosha]

Not sure what you mean there, as there is no tasty when compiling with 2.13.4.

So what I meant here is compiling this macro def with 3.0.0-M1:

implicit def mkTpeTag[T]: TpeTag[T] = macro TpeTagImpl.mkTag[T]

will produce the same tasty if class TpeTagImpl was compiled by either 2.13.4 or 3.0.0-M1, and also the byte code of class TpeTagImpl is not different when compiled by either version in anyway significant that I can see

I'm assuming that this is a tastyreader bug, that is, something that you need to be reading out of the tasty such that the compiler wires things correctly?

I'm not sure why there would be missing information given that it seems at the surface level that the same classfile is produced for TpeTagImpl by both compilers but further investigation would be required

[bishabosha]

I've updated the example so that TpeTagImpl is moved to be a top level class

[bishabosha]

same deal if we upgrade to 3.0.0-RC1 and 2.13.5