`inline def apply` throws unhandled exception

[erikerlandson]

Compiler version

3.4.0-RC2

Minimized code

object repro:
    abstract class Mapper[A, B] extends (A => B)

    given Mapper[Int, Double] with
        // inlining causes a compiler crash
        inline def apply(v: Int): Double = v.toDouble

Output (click arrow to expand)

  exception while retyping final module class given_Mapper_Int_Double() extends
  coulomb.repro.Mapper[Int, Double]() {
  private def writeReplace(): AnyRef =
    new scala.runtime.ModuleSerializationProxy(
      classOf[coulomb.repro.given_Mapper_Int_Double.type])
  inline def apply(v: Int): Double = this.apply$mcDI$sp(v)
  inline def apply$mcDI$sp(v: Int): Double = v.toDouble:Double
  private def apply$retainedBody(v: Int): Double = v.toDouble:Double
} of class TypeDef # -1

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/lampepfl/dotty/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: /home/eje/git/coulomb/core/src/main/scala/coulomb/quantity.scala
        during phase: MegaPhase{elimErasedValueType, pureStats, vcElideAllocations, etaReduce, arrayApply, elimPolyFunction, tailrec, completeJavaEnums, mixin, lazyVals, memoize, nonLocalReturns, capturedVars}
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.12
    compiler version: version 3.4.0-RC2
            settings: -Ykind-projector underscores -bootclasspath /home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.4.0-RC2/scala3-library_3-3.4.0-RC2.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar -classpath /home/eje/git/coulomb/core/.jvm/target/scala-3.4.0-RC2/classes:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/scalac-compat-annotation_3/0.1.4/scalac-compat-annotation_3-0.1.4.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/algebra_3/2.10.0/algebra_3-2.10.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire_3/0.18.0/spire_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/cats-kernel_3/2.10.0/cats-kernel_3-2.10.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-macros_3/0.18.0/spire-macros_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-platform_3/0.18.0/spire-platform_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-util_3/0.18.0/spire-util_3-0.18.0.jar -d /home/eje/git/coulomb/core/.jvm/target/scala-3.4.0-RC2/classes -deprecation true -feature true


  Exception while compiling /home/eje/git/coulomb/core/src/main/scala/coulomb/conversion/coefficients.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/conversion/conversion.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/conversion/standard/scala.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/conversion/standard/unit.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/conversion/standard/value.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/define/define.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/deltaquantity.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/infra/meta.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/infra/show.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/infra/typeexpr.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/infra/utils.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/ops/algebra/cats/all.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/ops/algebra/cats/deltaquantity.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/ops/algebra/cats/quantity.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/policy.scala, /home/eje/git/coulomb/core/src/main/scala/coulomb/quantity.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/lampepfl/dotty/issues/new/choose
  For non-enriched exceptions, compile with -Yno-enrich-error-messages.

     while compiling: <no file>
        during phase: parser
                mode: Mode()
     library version: version 2.13.12
    compiler version: version 3.4.0-RC2
            settings: -Ykind-projector underscores -bootclasspath /home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.4.0-RC2/scala3-library_3-3.4.0-RC2.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.12/scala-library-2.13.12.jar -classpath /home/eje/git/coulomb/core/.jvm/target/scala-3.4.0-RC2/classes:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/scalac-compat-annotation_3/0.1.4/scalac-compat-annotation_3-0.1.4.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/algebra_3/2.10.0/algebra_3-2.10.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire_3/0.18.0/spire_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/cats-kernel_3/2.10.0/cats-kernel_3-2.10.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-macros_3/0.18.0/spire-macros_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-platform_3/0.18.0/spire-platform_3-0.18.0.jar:/home/eje/.cache/coursier/v1/https/repo1.maven.org/maven2/org/typelevel/spire-util_3/0.18.0/spire-util_3-0.18.0.jar -d /home/eje/git/coulomb/core/.jvm/target/scala-3.4.0-RC2/classes -deprecation true -feature true

[error] ## Exception when compiling 16 sources to /home/eje/git/coulomb/core/.jvm/target/scala-3.4.0-RC2/classes
[error] java.util.NoSuchElementException: key not found: method apply$mcDI$sp
[error] scala.collection.immutable.Map$Map1.apply(Map.scala:263)
[error] dotty.tools.dotc.transform.Erasure$Typer.addRetainedInlineBodies$$anonfun$1(Erasure.scala:1019)
[error] scala.collection.immutable.List.mapConserve(List.scala:472)
[error] dotty.tools.dotc.transform.Erasure$Typer.addRetainedInlineBodies(Erasure.scala:1030)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1054)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2789)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1047)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3102)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3106)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3301)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3347)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1058)
[error] dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2789)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1047)
[error] dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3102)
[error] dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3106)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3301)
[error] dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3347)
[error] dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1058)
[error] dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2922)
[error] dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3148)
[error] dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3198)
[error] dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3391)
[error] dotty.tools.dotc.transform.Erasure.run(Erasure.scala:143)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.immutable.List.foreach(List.scala:333)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
[error] dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:348)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:357)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:357)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:267)
[error] dotty.tools.dotc.Driver.finish(Driver.scala:58)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:141)
[error] dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:193)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:248)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:183)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:211)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:180)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:178)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:464)
[error] sbt.internal.inc.IncrementalCommon$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$8(Incremental.scala:419)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:506)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:406)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:172)
[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:2371)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2321)
[error] sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:31)
[error] sbt.internal.io.Retry$.apply(Retry.scala:47)
[error] sbt.internal.io.Retry$.apply(Retry.scala:29)
[error] sbt.internal.io.Retry$.apply(Retry.scala:24)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2319)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:63)
[error] sbt.std.Transform$$anon$4.work(Transform.scala:69)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:283)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:24)
[error] sbt.Execute.work(Execute.scala:292)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:283)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:65)
[error] java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] java.base/java.util.concurrent.Executors$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$Worker.run(ThreadPoolExecutor.java:635)
[error] java.base/java.lang.Thread.run(Thread.java:840)
[error]            
[error] java.util.NoSuchElementException: key not found: method apply$mcDI$sp
[error] 	at scala.collection.immutable.Map$Map1.apply(Map.scala:263)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.addRetainedInlineBodies$$anonfun$1(Erasure.scala:1019)
[error] 	at scala.collection.immutable.List.mapConserve(List.scala:472)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.addRetainedInlineBodies(Erasure.scala:1030)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1054)
[error] 	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2789)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1047)
[error] 	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3102)
[error] 	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3106)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
[error] 	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3301)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3347)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1058)
[error] 	at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2789)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.typedClassDef(Erasure.scala:1047)
[error] 	at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:3102)
[error] 	at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:3106)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3197)
[error] 	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] 	at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:3301)
[error] 	at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3347)
[error] 	at dotty.tools.dotc.transform.Erasure$Typer.typedStats(Erasure.scala:1058)
[error] 	at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2922)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:3148)
[error] 	at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:3198)
[error] 	at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:174)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3275)
[error] 	at dotty.tools.dotc.typer.Typer.typed(Typer.scala:3279)
[error] 	at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3391)
[error] 	at dotty.tools.dotc.transform.Erasure.run(Erasure.scala:143)
[error] 	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:354)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at scala.collection.immutable.List.foreach(List.scala:333)
[error] 	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:360)
[error] 	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:315)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] 	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] 	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] 	at dotty.tools.dotc.Run.runPhases$1(Run.scala:337)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:348)
[error] 	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:357)
[error] 	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:71)
[error] 	at dotty.tools.dotc.Run.compileUnits(Run.scala:357)
[error] 	at dotty.tools.dotc.Run.compileUnits(Run.scala:267)
[error] 	at dotty.tools.dotc.Driver.finish(Driver.scala:58)
[error] 	at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] 	at dotty.tools.xsbt.CompilerBridgeDriver.run(CompilerBridgeDriver.java:141)
[error] 	at dotty.tools.xsbt.CompilerBridge.run(CompilerBridge.java:22)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:91)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:193)
[error] 	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:248)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:183)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:163)
[error] 	at sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:239)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:163)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:211)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:534)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:534)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:180)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:178)
[error] 	at sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:464)
[error] 	at sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] 	at sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] 	at sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] 	at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:263)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:419)
[error] 	at sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:506)
[error] 	at sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:406)
[error] 	at sbt.internal.inc.Incremental$.apply(Incremental.scala:172)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:534)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:488)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:425)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] 	at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2371)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2321)
[error] 	at sbt.internal.server.BspCompileTask$.$anonfun$compute$1(BspCompileTask.scala:31)
[error] 	at sbt.internal.io.Retry$.apply(Retry.scala:47)
[error] 	at sbt.internal.io.Retry$.apply(Retry.scala:29)
[error] 	at sbt.internal.io.Retry$.apply(Retry.scala:24)
[error] 	at sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2319)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:49)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:63)
[error] 	at sbt.std.Transform$$anon$4.work(Transform.scala:69)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:283)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:24)
[error] 	at sbt.Execute.work(Execute.scala:292)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:283)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:265)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:65)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] 	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
[error] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
[error] 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
[error] 	at java.base/java.lang.Thread.run(Thread.java:840)
[error] (coreJVM / Compile / compileIncremental) java.util.NoSuchElementException: key not found: method apply$mcDI$sp
[error] Total time: 10 s, completed Feb 18, 2024, 10:19:00 AM
eje@localhost:~/git/coulomb$ 

[erikerlandson]

It works if class does not inherit from A => B

object repro:
    // works when Mapper does not extend A=>B
    abstract class Mapper[A, B]:
        def apply(a: A): B

    given Mapper[Int, Double] with
        inline def apply(v: Int): Double = v.toDouble

[nicolasstucki]

Minimization

class MyMapper extends (Int => Double):
    inline def apply(v: Int): Double = v.toDouble

[nicolasstucki]

It seems there is a buggy interaction between function specialization and retained inlines.

  exception while retyping 
    class MyMapper() extends Object(), (Int => Double) {
      inline def apply(v: Int): Double = this.apply$mcDI$sp(v)
      inline def apply$mcDI$sp(v: Int): Double = v.toDouble:Double
      private def apply$retainedBody(v: Int): Double = v.toDouble:Double
    }

[nicolasstucki]

We probably need to generate an apply$mcDI$sp$retainedBody method when specializing functions (SpecializeFunctions).

[nicolasstucki]

We also do not need to specialize the inline version of the method.

[mbovel]

This issue was picked for the Issue Spree of Februrary 27th, 2024. @nicolasstucki, @EugeneFlesselle, @SethTisue and @nmcb will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.

[SethTisue]

We also do not need to specialize the inline version of the method.

As far as we can see, this is as simple as adding an is(Inline) check to the SpecializeFunctions mini phase.

This change isn't actually necessary to fix the bug, as the extra specialized method ends up disappearing during erasure anyway, but I agree it's worth doing while we're messing with this.

[SethTisue]

As for the main change, this will also be in SpecializeFunctions, specifically in transformDefDef.

It's a bit complicated because of the way the $retainedBody dance works, as Nico explained to us. Early in compilation, we have inline def apply and private def apply$retainedBody. Then at erasure (?), the inline def apply goes away and the apply$retainedBody takes it place, with $retainedBody removed from the name.

We are provisionally thinking that to be consistent with the handling of non-specialized inline methods, it seems best to generate apply$mcDI$sp$retainedBody and then let erasure rename it later (and make it public), rather than generate the desired final code directly. (If we sometimes do this weird dance, we should always do it?)