Reflection regression from 2.13.0-M2(or 2.12.4) to 2.13.0-M3, 2.13.0-M4 #10758
Description
Update:
Thanks to @retronym we know the first regression for 2.13.0-M3 occurred at the following commit scala/scala@dd31672 of this PR scala/scala#6140
The second regression added another error for 2.13.0-M4, but maybe it's a side-effect of the primary issue.
Minimized at https://github.com/soronpo/ScalaRegression
Macros.scala
import scala.reflect.macros.whitebox.Context
final class TwoFaceInt[T](val value : Int) {
def + [R](that : TwoFaceInt[R]) = ???
}
object TwoFaceInt {
def apply[T <: Int, Out <: T](value : T) : TwoFaceInt[Out] = macro Builder.Macro.fromNumValue[T]
}
object Builder {
final class Macro(val c: Context) {
def fromNumValue[T](value : c.Tree)(implicit t : c.WeakTypeTag[T]) : c.Tree = {
import c.universe._
val tTpe = weakTypeOf[T]
val valueTpe = value match {
case Literal(Constant(t : Int)) => c.internal.constantType(Constant(t))
case _ => tTpe
}
q"new TwoFaceInt[$valueTpe]($value)"
}
}
}Test.scala
object Test {
TwoFaceInt(1) + TwoFaceInt(2)
}✅ 2.12.4
✅ 2.12.6
✅ 2.13.0-M2
❌ 2.13.0-M3 with one error:
[error] /Test.scala:2: type mismatch;
[error] found : TwoFaceInt[Int(2)]
[error] required: TwoFaceInt[Nothing]
[error] Note: Int(2) >: Nothing, but class TwoFaceInt is invariant in type T.
[error] You may wish to define T as -T instead. (SLS 4.5)
[error] TwoFaceInt(1) + TwoFaceInt(2)
[error] ^
[error] one error found
❌ 2.13.0-M4 with two errors:
[error] /Test.scala:2: type mismatch;
[error] found : TwoFaceInt[Int(2)]
[error] required: TwoFaceInt[Nothing]
[error] Note: Int(2) >: Nothing, but class TwoFaceInt is invariant in type T.
[error] You may wish to define T as -T instead. (SLS 4.5)
[error] TwoFaceInt(1) + TwoFaceInt(2)
[error] ^
[error] /Test.scala:2: type mismatch;
[error] found : TwoFaceInt[Int(1)]
[error] required: TwoFaceInt[Nothing]
[error] Note: Int(1) >: Nothing, but class TwoFaceInt is invariant in type T.
[error] You may wish to define T as -T instead. (SLS 4.5)
[error] TwoFaceInt(1) + TwoFaceInt(2)
[error] ^
[error] two errors found