`null` used as prefix of type application during implicit search

[Katrix]

Encountered this when I got the priorization of implicits slightly wrong. Swapping fromTuple and tupleFromMirrorAndLength makes it work fine in this case. Not actually sure what the bug is here. This is as small as I could minimize it

Compiler version

3.3.1

If you're not sure what version you're using, run print scalaVersion from sbt
(if you're running scalac manually, use scalac -version instead).

Minimized code

import scala.annotation.{tailrec, unused}
import scala.deriving.Mirror
import scala.quoted.*

trait TypeLength[A] {
  type Length <: Int
  def length: Length
}
object TypeLength extends TypeLengthLowPriority:
  type Aux[A, Length0 <: Int] = TypeLength[A] {
    type Length = Length0
  }

  transparent inline given fromMirror[A](using m: Mirror.Of[A]): TypeLength[A] =
    ${ macroImpl[A, m.MirroredElemTypes] }

  @tailrec
  private def typesOfTuple(
      using q: Quotes
  )(tpe: q.reflect.TypeRepr, acc: List[q.reflect.TypeRepr]): List[q.reflect.TypeRepr] =
    import q.reflect.*
    val cons = Symbol.classSymbol("scala.*:")
    tpe.widenTermRefByName.dealias match
      case AppliedType(fn, tpes) if defn.isTupleClass(fn.typeSymbol) =>
        tpes.reverse_:::(acc)
      case AppliedType(tp, List(headType, tailType)) if tp.derivesFrom(cons) =>
        typesOfTuple(tailType, headType :: acc)
      case tpe =>
        if tpe.derivesFrom(Symbol.classSymbol("scala.EmptyTuple")) then acc.reverse
        else report.errorAndAbort(s"Unknown type encountered in tuple ${tpe.show}")

  def macroImpl[A: Type, T <: Tuple: scala.quoted.Type](
      using q: scala.quoted.Quotes
  ): scala.quoted.Expr[TypeLength[A]] =
    import q.reflect.*
    val l = typesOfTuple(TypeRepr.of[T], Nil).length
    ConstantType(IntConstant(l)).asType match
      case '[lt] =>
        val le = Expr[Int](l).asExprOf[lt & Int]
        '{
          val r: TypeLength.Aux[A, lt & Int] = new TypeLength[A] {
            type Length = lt & Int
            val length: Length = ${ le }
          }
          r
        }

  transparent inline given fromTuple[T <: Tuple]: TypeLength[T] =
    ${ macroImpl[T, T] }

trait TypeLengthLowPriority:
  self: TypeLength.type =>
  given tupleFromMirrorAndLength[A, T <: Tuple](
      using @unused m: Mirror.Of[A] { type MirroredElemTypes = T },
      length: TypeLength[A]
  ): TypeLength.Aux[T, length.Length] = length.asInstanceOf[TypeLength.Aux[T, length.Length]]

trait HKDSumGeneric[A]
object HKDSumGeneric:
  type NotZero[N <: Int] = N match
    case 0 => false
    case _ => true

  transparent inline given derived[A](using m: Mirror.SumOf[A], typeLength: TypeLength[A])(
      using NotZero[typeLength.Length] =:= true
  ): HKDSumGeneric[A] =
    derivedImpl[A, m.MirroredElemTypes, m.MirroredLabel]

  def derivedImpl[A, ElemTypes <: Tuple, Label <: String](
      using m: Mirror.SumOf[A] {
        type MirroredElemTypes = ElemTypes; type MirroredLabel = Label;
      },
      typeLength: TypeLength[ElemTypes],
      nz: NotZero[typeLength.Length] =:= true
  ): HKDSumGeneric[A] = ???

Output (click arrow to expand)

java.lang.AssertionError: assertion failed while typechecking D:\DevProjects\Stable\perspective\dotty\derivation\src\main\scala\perspective\derivation\test1.scala
[info] exception occurred while typechecking D:\DevProjects\Stable\perspective\dotty\derivation\src\main\scala\perspective\derivation\test1.scala
[info]
[info]   exception occurred while compiling List(D:\DevProjects\Stable\perspective\dotty\derivation\src\main\scala\perspective\derivation\test1.scala)
[info]
[info]   An unhandled exception was thrown in the compiler.
[info]   Please file a crash report here:
[info]   https://github.com/lampepfl/dotty/issues/new/choose
[info]
[info]      while compiling: <no file>
[info]         during phase: <no phase>
[info]                 mode: Mode(ImplicitsEnabled)
[info]      library version: version 2.13.10
[info]     compiler version: version 3.3.1
[info]             settings: -Ykind-projector "" -bootclasspath C:\Users\katri\AppData\Local\Coursier\Cache\v1\https\repo1.maven.org\maven2\org\scala-lang\scala3-library_3\3.3.1\scala3-library_3-3.3.1.jar;C:\Users\katri\AppData\Local\Coursier\Cache\v1\https\repo1.maven.org\maven2\org\scala-lang\scala-library\2.13.10\scala-library-2.13.10.jar -classpath D:\DevProjects\Stable\perspective\dotty\derivation\target\scala-3.3.1\classes;D:\DevProjects\Stable\perspective\dotty\perspective\target\scala-3.3.1\classes;C:\Users\katri\AppData\Local\Coursier\Cache\v1\https\repo1.maven.org\maven2\org\typelevel\cats-core_3\2.8.0\cats-core_3-2.8.0.jar;C:\Users\katri\AppData\Local\Coursier\Cache\v1\https\repo1.maven.org\maven2\org\typelevel\cats-kernel_3\2.8.0\cats-kernel_3-2.8.0.jar -d D:\DevProjects\Stable\perspective\dotty\derivation\target\scala-3.3.1\classes -feature true
[info]
[info]                 tree: EmptyTree
[info]        tree position: :<unknown>
[info]            tree type: <notype>
[info]               symbol: val <none>
[info]            call site: package <root> in module class <root>
[info]
[info]   == Source file context for tree position ==
[info]
[error] ## Exception when compiling 11 sources to D:\DevProjects\Stable\perspective\dotty\derivation\target\scala-3.3.1\classes
[error] java.lang.AssertionError: assertion failed
[error] scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
[error] dotty.tools.dotc.ast.tpd$.TypeApply(tpd.scala:60)
[error] dotty.tools.dotc.ast.tpd$TreeOps$.appliedToTypeTrees$extension(tpd.scala:985)
[error] dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:4255)
[error] dotty.tools.dotc.typer.Typer.adapt(Typer.scala:3587)
[error] dotty.tools.dotc.typer.ProtoTypes$FunProto.typedArg(ProtoTypes.scala:497)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:897)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.typedArg(Applications.scala:897)
[error] dotty.tools.dotc.typer.Applications$Application.addTyped$1(Applications.scala:589)
[error] dotty.tools.dotc.typer.Applications$Application.matchArgs(Applications.scala:653)
[error] dotty.tools.dotc.typer.Applications$Application.init(Applications.scala:492)
[error] dotty.tools.dotc.typer.Applications$TypedApply.<init>(Applications.scala:779)
[error] dotty.tools.dotc.typer.Applications$ApplyToUntyped.<init>(Applications.scala:896)
[error] dotty.tools.dotc.typer.Applications.ApplyTo(Applications.scala:1126)
[error] dotty.tools.dotc.typer.Applications.ApplyTo$(Applications.scala:352)
[error] dotty.tools.dotc.typer.Typer.ApplyTo(Typer.scala:116)
[error] dotty.tools.dotc.typer.Applications.simpleApply$1(Applications.scala:969)
[error] dotty.tools.dotc.typer.Applications.realApply$1$$anonfun$2(Applications.scala:1052)
[error] dotty.tools.dotc.typer.Typer.tryEither(Typer.scala:3324)
[error] dotty.tools.dotc.typer.Applications.realApply$1(Applications.scala:1063)
[error] dotty.tools.dotc.typer.Applications.typedApply(Applications.scala:1101)
[error] dotty.tools.dotc.typer.Applications.typedApply$(Applications.scala:352)
[error] dotty.tools.dotc.typer.Typer.typedApply(Typer.scala:116)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3048)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3112)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3184)
[error] dotty.tools.dotc.typer.Implicits.tryConversion$1(Implicits.scala:1136)
[error] dotty.tools.dotc.typer.Implicits.typedImplicit(Implicits.scala:1167)
[error] dotty.tools.dotc.typer.Implicits.typedImplicit$(Implicits.scala:818)
[error] dotty.tools.dotc.typer.Typer.typedImplicit(Typer.scala:116)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.tryImplicit(Implicits.scala:1242)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.rank$1(Implicits.scala:1341)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:1511)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:1539)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.searchImplicit(Implicits.scala:1547)
[error] dotty.tools.dotc.typer.Implicits$ImplicitSearch.bestImplicit(Implicits.scala:1572)
[error] dotty.tools.dotc.typer.Implicits.inferImplicit(Implicits.scala:1060)
[error] dotty.tools.dotc.typer.Implicits.inferImplicit$(Implicits.scala:818)
[error] dotty.tools.dotc.typer.Typer.inferImplicit(Typer.scala:116)
[error] dotty.tools.dotc.typer.Implicits.inferView(Implicits.scala:856)
[error] dotty.tools.dotc.typer.Implicits.inferView$(Implicits.scala:818)
[error] dotty.tools.dotc.typer.Typer.inferView(Typer.scala:116)
[error] dotty.tools.dotc.typer.Implicits.viewExists(Implicits.scala:831)
[error] dotty.tools.dotc.typer.Implicits.viewExists$(Implicits.scala:818)
[error] dotty.tools.dotc.typer.Typer.viewExists(Typer.scala:116)
[error] dotty.tools.dotc.typer.Implicits.ignoredConvertibleImplicits$1$$anonfun$3(Implicits.scala:960)
[error] scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:479)
[error] scala.collection.Iterator.isEmpty(Iterator.scala:466)
[error] scala.collection.Iterator.isEmpty$(Iterator.scala:466)
[error] scala.collection.AbstractIterator.isEmpty(Iterator.scala:1300)
[error] scala.collection.View$Filter.isEmpty(View.scala:146)
[error] scala.collection.IterableOnceOps.nonEmpty(IterableOnce.scala:833)
[error] scala.collection.IterableOnceOps.nonEmpty$(IterableOnce.scala:833)
[error] scala.collection.AbstractIterable.nonEmpty(Iterable.scala:933)
[error] dotty.tools.dotc.reporting.MissingImplicitArgument.noChainConversionsNote$1(messages.scala:2838)
[error] dotty.tools.dotc.reporting.MissingImplicitArgument.msgPostscript$$anonfun$4(messages.scala:2846)
[error] scala.Option.orElse(Option.scala:477)
[error] dotty.tools.dotc.reporting.MissingImplicitArgument.msgPostscript(messages.scala:2846)
[error] dotty.tools.dotc.reporting.Message.message$$anonfun$1(Message.scala:345)
[error] dotty.tools.dotc.reporting.Message.inMessageContext(Message.scala:341)
[error] dotty.tools.dotc.reporting.Message.message(Message.scala:345)
[error] dotty.tools.dotc.reporting.Message.isNonSensical(Message.scala:322)
[error] dotty.tools.dotc.reporting.HideNonSensicalMessages.isHidden(HideNonSensicalMessages.scala:16)
[error] dotty.tools.dotc.reporting.HideNonSensicalMessages.isHidden$(HideNonSensicalMessages.scala:10)
[error] dotty.tools.dotc.reporting.AbstractReporter.isHidden(AbstractReporter.scala:8)
[error] dotty.tools.dotc.reporting.Reporter.issueUnconfigured(Reporter.scala:156)
[error] dotty.tools.dotc.reporting.Reporter.go$1(Reporter.scala:181)
[error] dotty.tools.dotc.reporting.Reporter.issueIfNotSuppressed(Reporter.scala:200)
[error] dotty.tools.dotc.reporting.Reporter.report(Reporter.scala:203)
[error] dotty.tools.dotc.report$.error(report.scala:68)
[error] dotty.tools.dotc.typer.Typer.issueErrors$1$$anonfun$1(Typer.scala:3808)
[error] scala.runtime.function.JProcedure3.apply(JProcedure3.java:15)
[error] scala.runtime.function.JProcedure3.apply(JProcedure3.java:10)
[error] scala.collection.LazyZip3.foreach(LazyZipOps.scala:248)
[error] dotty.tools.dotc.typer.Typer.issueErrors$1(Typer.scala:3810)
[error] dotty.tools.dotc.typer.Typer.addImplicitArgs$1(Typer.scala:3832)
[error] dotty.tools.dotc.typer.Typer.adaptNoArgsImplicitMethod$1(Typer.scala:3849)
[error] dotty.tools.dotc.typer.Typer.adaptNoArgs$1(Typer.scala:4038)
[error] dotty.tools.dotc.typer.Typer.adapt1(Typer.scala:4268)
[error] dotty.tools.dotc.typer.Typer.adapt(Typer.scala:3587)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3184)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3188)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3300)
[error] dotty.tools.dotc.typer.Typer.$anonfun$57(Typer.scala:2486)
[error] dotty.tools.dotc.inlines.PrepareInlineable$.dropInlineIfError(PrepareInlineable.scala:243)
[error] dotty.tools.dotc.typer.Typer.typedDefDef(Typer.scala:2486)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3024)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3111)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3184)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3188)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3210)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3256)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2669)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3036)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3040)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3111)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3184)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3188)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3210)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3256)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2812)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3081)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3112)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3184)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3188)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3300)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$1(TyperPhase.scala:44)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck$$anonfun$adapted$1(TyperPhase.scala:54)
[error] scala.Function0.apply$mcV$sp(Function0.scala:42)
[error] dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:440)
[error] dotty.tools.dotc.typer.TyperPhase.typeCheck(TyperPhase.scala:54)
[error] dotty.tools.dotc.typer.TyperPhase.runOn$$anonfun$3(TyperPhase.scala:88)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.typer.TyperPhase.runOn(TyperPhase.scala:88)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:246)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1321)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:262)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:270)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:279)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:67)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:279)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:194)
[error] dotty.tools.dotc.Run.compile(Run.scala:179)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:88)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:193)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:248)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:183)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:211)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:179)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:177)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:463)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:418)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:506)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:405)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:171)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:488)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:425)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2364)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2314)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:30)
[error] sbt.internal.io.Retry$.apply(Retry.scala:46)
[error] sbt.internal.io.Retry$.apply(Retry.scala:28)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:30)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2312)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:62)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:68)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:282)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:23)
[error] sbt.Execute.work(Execute.scala:291)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:282)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:64)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
[error] java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
[error] java.base/java.lang.Thread.run(Thread.java:833)

[nicolasstucki]

With the improved error message in #18700 we get the following failure

Exception in thread "main" java.lang.AssertionError: assertion failed: Illegal TypeApply function prefix: Literal(Constant(null))
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.ast.tpd$.TypeApply(tpd.scala:61)
        at dotty.tools.dotc.ast.tpd$TreeOps$.appliedToTypeTrees$extension(tpd.scala:993)

The macro is attempting to create the AST null[A].

[nicolasstucki]

Minimized

trait Foo { type Num <: Int }
given derived[A](using foo: Foo): Any = derivedImpl(foo)
def derivedImpl(foo: Foo)(using bar: foo.Num =:= Int): Any = ???

[smarter]

The null comes from dummyTreeOfType in https://github.com/lampepfl/dotty/blob/15033c7ac8be33a1b94226da3cca3922b53066ce/compiler/src/dotty/tools/dotc/typer/Implicits.scala#L855
Can we simply add a check beforehand that does !from.widen.isInstanceOf[MethodicType] ?

[dwijnand]

We have. #18719