Cannot Use a Mirror Summoned via summonExpr

[deusaquilus]

minimized code

Let's say I have a simple json encoder, for the sake of example it can be any kind of encoder that uses derived.

package derivation
import scala.deriving._
import scala.compiletime.erasedValue

trait JsonEncoder[T] {
  def encode(elem: T): String
}

object JsonEncoder {
  import scala.compiletime.{erasedValue, summonFrom}
  import compiletime._
  import scala.deriving._

  inline def encodeElem[T](elem: T): String = summonFrom {
    case encoder: JsonEncoder[T] => encoder.encode(elem)
  }

  inline def encodeElems[Elems <: Tuple](idx: Int)(value: Any): List[String] =
    inline erasedValue[Elems] match {
      case _: (elem *: elems1) => 
        encodeElem[elem](productElement[elem](value, idx)) :: encodeElems[elems1](idx + 1)(value)
      case _ => Nil
    }

  inline def derived[T](implicit ev: Mirror.Of[T]): JsonEncoder[T] = new JsonEncoder[T] {
    def encode(value: T): String = 
      inline ev match {
        case m: Mirror.SumOf[T] =>
          "not supporting this case yet"
        case m: Mirror.ProductOf[T] =>
          val elems = encodeElems[m.MirroredElemTypes](0)(value)
          val labels = value.asInstanceOf[Product].productElementNames
          val keyValues = labels.zip(elems).map((k, v) => s"$k: $v")
          "{" + (keyValues).mkString(", ") + "}"
        case other =>
          throw new RuntimeException("mirror was an invalid value: " + other)
      }
  }

  given listEncoder[T]: (encoder: JsonEncoder[T]) => JsonEncoder[List[T]] {
    def encode(list: List[T]) = s"[${ list.map(v => encoder.encode(v)).mkString(", ") }]"
  }

  given intEncoder: JsonEncoder[Int] {
    def encode(value: Int) = value + ""
  }

  given stringEncoder: JsonEncoder[String] {
    def encode(value: String) = value
  }
}

Now, inside of a macro, I want to be able to take an abitrary type, summon the mirror for it, and then use the encoder.

package derivation

import scala.deriving._
import scala.quoted._
import scala.quoted.matching._
import scala.compiletime.{erasedValue, summonFrom}

object SummonJsonEncoderTest {

  inline def encodeAndMessAroundType[T](value: =>T): String = ${ encodeAndMessAroundTypeImpl('value) }
  def encodeAndMessAroundTypeImpl[T: Type](value: Expr[T])(given qctx: QuoteContext): Expr[String] = {
    import qctx.tasty._
    val mirrorExpr = summonExpr[Mirror.Of[T]] match {
      case Some(mirror) => mirror
    }

    '{
      given JsonEncoder[T] = JsonEncoder.derived($mirrorExpr)
      val encoder = summon[JsonEncoder[T]]
      encoder.encode($value)
    }
  }

Then let's say I use this in some "client-facing" code:

package derivation
case class PersonSimple(name:String, age:Int)
object SummonTest {
  val stuff = PersonSimple("Joe", 123)
  def main(args: Array[String]):Unit = {
    println( SummonJsonEncoderTest.encodeAndMessAroundType(stuff) )
  }
}

expectation

The above code should work. Instead, it causes the error:

[error]    # 282684 of class dotty.tools.dotc.ast.Trees$Typed in /home/alexander/git/dotty/dotty_test/src/main/scala/derivation/SummonJsonEncoderTest.scala
[error]         at dotty.DottyPredef$.assertFail(DottyPredef.scala:17)
[error]         at dotty.tools.dotc.typer.Typer$.assertPositioned(Typer.scala:60)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2209)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedTypeApply(Erasure.scala:537)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2137)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedInlined(Typer.scala:1342)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedInlined(Erasure.scala:595)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2140)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.typer.Typer.typedValDef(Typer.scala:1588)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedValDef(Erasure.scala:603)
[error]         at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2103)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
[error]         at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:747)
[error]         at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:785)
[error]         at dotty.tools.dotc.typer.Typer.typedInlined(Typer.scala:1341)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedInlined(Erasure.scala:595)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2140)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:1653)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedDefDef(Erasure.scala:635)
[error]         at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2106)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
[error]         at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:747)
[error]         at dotty.tools.dotc.typer.Typer.typedBlockStats(Typer.scala:785)
[error]         at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:789)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2127)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedInlined(Typer.scala:1342)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedInlined(Erasure.scala:595)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2140)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedTyped(Erasure.scala:393)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2124)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2211)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedInlined(Typer.scala:1342)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedInlined(Erasure.scala:595)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2140)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.$anonfun$5(Erasure.scala:564)
[error]         at dotty.tools.dotc.core.Decorators$ListDecorator$.zipWithConserve$extension(Decorators.scala:110)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedApply(Erasure.scala:564)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2119)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.typer.Typer.typedBlock(Typer.scala:790)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2127)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:1653)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedDefDef(Erasure.scala:635)
[error]         at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2106)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
[error]         at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:747)
[error]         at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:1784)
[error]         at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2109)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2176)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2247)
[error]         at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:2291)
[error]         at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:747)
[error]         at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:1910)
[error]         at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2150)
[error]         at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2177)
[error]         at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:123)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2213)
[error]         at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2225)
[error]         at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:2333)
[error]         at dotty.tools.dotc.transform.Erasure.run(Erasure.scala:100)
[error]         at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:315)
[error]         at scala.collection.immutable.List.map(List.scala:219)
[error]         at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:316)
[error]         at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:161)
[error]         at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error]         at dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error]         at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error]         at dotty.tools.dotc.Run.runPhases$5(Run.scala:171)
[error]         at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:179)
[error]         at dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error]         at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:65)
[error]         at dotty.tools.dotc.Run.compileUnits(Run.scala:186)
[error]         at dotty.tools.dotc.Run.compileUnits(Run.scala:128)
[error]         at dotty.tools.dotc.Driver.finish$1(Driver.scala:46)
[error]         at dotty.tools.dotc.Driver.doCompile(Driver.scala:49)
[error]         at dotty.tools.dotc.Driver.process(Driver.scala:189)
[error]         at dotty.tools.dotc.Main.process(Main.scala)
[error]         at xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
[error]         at xsbt.CompilerInterface.run(CompilerInterface.java:41)
[error]         at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
[error]         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error]         at java.lang.reflect.Method.invoke(Method.java:498)
[error]         at sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:237)
[error]         at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:111)
[error]         at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:90)
[error]         at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error]         at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error]         at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:133)
[error]         at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:73)
[error]         at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:116)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:307)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:307)
[error]         at sbt.internal.inc.Incremental$.doCompile(Incremental.scala:106)
[error]         at sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:87)
[error]         at sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:116)
[error]         at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:63)
[error]         at sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:89)
[error]         at sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:134)
[error]         at sbt.internal.inc.Incremental$.compile(Incremental.scala:80)
[error]         at sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:67)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:311)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:269)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:159)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:238)
[error]         at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:69)
[error]         at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1549)
[error]         at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1523)
[error]         at scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error]         at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:40)
[error]         at sbt.std.Transform$$anon$4.work(System.scala:67)
[error]         at sbt.Execute.$anonfun$submit$2(Execute.scala:269)
[error]         at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error]         at sbt.Execute.work(Execute.scala:278)
[error]         at sbt.Execute.$anonfun$submit$1(Execute.scala:269)
[error]         at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error]         at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error]         at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error]         at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error]         at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error]         at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error]         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error]         at java.lang.Thread.run(Thread.java:748)
[error] (Compile / compileIncremental) java.lang.AssertionError: assertion failed: position not set for derivation.PersonSimple:
[error]   
[error]     (
[error]       scala.deriving.Mirror{
[error]         MirroredType = derivation.PersonSimple; 
[error]           MirroredMonoType = derivation.PersonSimple
[error]         ; MirroredElemTypes <: Tuple
[error]       }
[error]      & 
[error]       scala.deriving.Mirror.Product{
[error]         MirroredMonoType = derivation.PersonSimple; 
[error]           MirroredType = derivation.PersonSimple
[error]         ; MirroredLabel = ("PersonSimple" : String)
[error]       }
[error]     ){
[error]       MirroredElemTypes = (String, Int); 
[error]         MirroredElemLabels = (("name" : String), ("age" : String))
[error]     }
[error]    # 282684 of class dotty.tools.dotc.ast.Trees$Typed in /home/alexander/git/dotty/dotty_test/src/main/scala/derivation/SummonJsonEncoderTest.scala
[error] Total time: 1 s, completed Dec 26, 2019 5:24:45 PM

[nicolasstucki]

It looks like it is already fixed on master

[deusaquilus]

Okay, thanks. Where can I grab the overnight build and try it out?

[deusaquilus]

Wait a minute, are you sure this is working I'm running 0.22.0-bin-20200110-842e4c4-NIGHTLY and getting this error:

[error] java.lang.RuntimeException: mirror was an invalid value: <function2>
[error]         at derivation.Test$$anon$1.encode(SummonTest.scala:12)
[error]         at derivation.Test$$anon$1.encode(SummonTest.scala:12)
[error]         at derivation.Test$.main(SummonTest.scala:12)
[error]         at derivation.Test.main(SummonTest.scala)
[error]         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error]         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error]         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error]         at java.lang.reflect.Method.invoke(Method.java:498)
[error] Nonzero exit code: 1

[nicolasstucki]

That seems to be another error. Is the code bug free? Is the compiler generating wrong code? Maybe open another issue.

[deusaquilus]

I used the same code as found in @liufengyun's posted code here.

[nicolasstucki]

This line should probably be a compile time error.

[nicolasstucki]

Oh, it cannot fin the mirror and then defaults to any implicit it finds. That is where the function2 comes from. Maybe just remove that case.

[deusaquilus]

That causes:

[error]    |  cannot reduce inline match with
[error]    |   scrutinee:  {
[error]    |    ev
[error]    |  } : (ev : 
[error]    |    scala.deriving.Mirror{
[error]    |      MirroredType = T; MirroredMonoType = T; MirroredElemTypes <: Tuple
[error]    |    }
[error]    |  )
[error]    |   patterns :  case m @ _:deriving.Mirror.SumOf[T]
[error]    |               case m @ _:deriving.Mirror.ProductOf[T]
[error]    | This location contains code that was inlined from JsonEncoder.scala:28
[error] -- Error: /home/alexander/git/dotty/mirror_test/src/main/scala/org/deusaquilus/Test.scala:11:57 
[error] 11 |    println(SummonJsonEncoderTest.encodeAndMessAroundType(stuff) )

I'll post the exact code to a repo in a second.

[deusaquilus]

Here's the exact code:
https://github.com/deusaquilus/mirror_test

[deusaquilus]

Please have a look at #7974