NoSuchElementException when lifting a Type

[IndiscriminateCoding]

Minimized code

import scala.quoted._

object T {
  def impl[A](using t: Type[A])(using ctx: QuoteContext): Expr[Unit] = {
    Expr.summon[t.Underlying]
    '{}
  }
}

Output

[error] ## Exception when compiling 8 sources to /home/<redacted>/target/scala-3.0.0-M1/classes
[error] java.util.NoSuchElementException: None.get
[error] scala.None$.get(Option.scala:627)
[error] scala.None$.get(Option.scala:626)
[error] dotty.tools.dotc.core.StagingContext$.getQuoteTypeTags(StagingContext.scala:48)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transformSpliceType(PCPCheckAndHeal.scala:143)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:130)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform$$anonfun$2(Trees.scala:1372)
[error] scala.collection.immutable.List.mapConserve(List.scala:472)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1372)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1275)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:121)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1273)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:121)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1273)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:121)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform$$anonfun$2(Trees.scala:1372)
[error] scala.collection.immutable.List.mapConserve(List.scala:472)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1372)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transformStats(Trees.scala:1370)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1287)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:92)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:136)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:100)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.traverse$1(TreeMapWithImplicits.scala:53)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transformStats(TreeMapWithImplicits.scala:60)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:112)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1350)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:105)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform$$anonfun$2(Trees.scala:1372)
[error] scala.collection.immutable.List.mapConserve(List.scala:472)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1372)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transformStats(Trees.scala:1370)
[error] dotty.tools.dotc.ast.Trees$Instance$TreeMap.transform(Trees.scala:1357)
[error] dotty.tools.dotc.ast.TreeMapWithImplicits.transform(TreeMapWithImplicits.scala:105)
[error] dotty.tools.dotc.transform.TreeMapWithStages.mapOverTree$1(TreeMapWithStages.scala:85)
[error] dotty.tools.dotc.transform.TreeMapWithStages.transform(TreeMapWithStages.scala:148)
[error] dotty.tools.dotc.transform.PCPCheckAndHeal.transform(PCPCheckAndHeal.scala:67)
[error] dotty.tools.dotc.transform.Staging$$anon$2.transform(Staging.scala:80)
[error] dotty.tools.dotc.transform.MacroTransform.run(MacroTransform.scala:21)
[error] dotty.tools.dotc.transform.Staging.run(Staging.scala:76)
[error] dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:296)
[error] scala.collection.immutable.List.map(List.scala:246)
[error] dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:297)
[error] dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:185)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[error] dotty.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[error] scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[error] dotty.tools.dotc.Run.runPhases$5(Run.scala:195)
[error] dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:203)
[error] dotty.runtime.function.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:67)
[error] dotty.tools.dotc.Run.compileUnits(Run.scala:210)
[error] dotty.tools.dotc.Run.compileSources(Run.scala:147)
[error] dotty.tools.dotc.Run.compile(Run.scala:129)
[error] dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
[error] dotty.tools.dotc.Driver.process(Driver.scala:194)
[error] dotty.tools.dotc.Main.process(Main.scala)
[error] xsbt.CachedCompilerImpl.run(CachedCompilerImpl.java:69)
[error] xsbt.CompilerInterface.run(CompilerInterface.java:41)
[error] sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
[error] sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] java.lang.reflect.Method.invoke(Method.java:498)
[error] sbt.internal.inc.AnalyzingCompiler.invoke(AnalyzingCompiler.scala:330)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:113)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$7(MixedAnalyzingCompiler.scala:186)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:241)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:176)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4$adapted(MixedAnalyzingCompiler.scala:157)
[error] sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:232)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:157)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:204)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:571)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:571)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5(Incremental.scala:174)
[error] sbt.internal.inc.Incremental$.$anonfun$apply$5$adapted(Incremental.scala:172)
[error] sbt.internal.inc.Incremental$$anon$2.run(Incremental.scala:459)
[error] sbt.internal.inc.IncrementalCommon$CycleState.next(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:56)
[error] sbt.internal.inc.IncrementalCommon$$anon$1.next(IncrementalCommon.scala:52)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:261)
[error] sbt.internal.inc.Incremental$.$anonfun$incrementalCompile$8(Incremental.scala:414)
[error] sbt.internal.inc.Incremental$.withClassfileManager(Incremental.scala:499)
[error] sbt.internal.inc.Incremental$.incrementalCompile(Incremental.scala:401)
[error] sbt.internal.inc.Incremental$.apply(Incremental.scala:166)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:571)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:489)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:332)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:419)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:137)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:2143)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$2(Defaults.scala:2100)
[error] sbt.internal.io.Retry$.apply(Retry.scala:40)
[error] sbt.internal.io.Retry$.apply(Retry.scala:23)
[error] sbt.internal.server.BspCompileTask$.compute(BspCompileTask.scala:31)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:2096)
[error] scala.Function1.$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$2.call(CompletionService.scala:64)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] java.lang.Thread.run(Thread.java:748)
[error]            
[error] stack trace is suppressed; run last Compile / compileIncremental for the full output
[error] (Compile / compileIncremental) java.util.NoSuchElementException: None.get
[error] Total time: 1 s, completed Oct 30, 2020 9:25:53 PM

Expectation

[nicolasstucki]

Workaround and ideal code:

import scala.quoted._
object T {
  def impl[A: Type](using ctx: QuoteContext): Expr[Unit] = {
    Expr.summon[A]
    '{}
  }
}

[IndiscriminateCoding]

@nicolasstucki while ideal, it is not always possible.
My actual use case involves existential type parameter, and the only workaround that I found involves local abstract type and asInstanceOf usage

[nicolasstucki]

Could you provide an example?

[IndiscriminateCoding]

@nicolasstucki something like that

import scala.quoted._

case class T(t: Type[_])

object T {
  def impl[A](t: T)(using ctx: QuoteContext): Expr[Unit] = {
    Expr.summon[t.t.Underlying]
    '{}
  }
}

[nicolasstucki]

In those cases you can give it a name using a quote pattern

import scala.quoted._

case class T(t: Type[_ <: Any])

object T {
  def impl[A](t: T)(using Quotes): Expr[Unit] = {
    t.t match
      case '[x] =>
        Expr.summon[x]
    '{}
  }
}

[IndiscriminateCoding]

@nicolasstucki while trying to adapt my code to your example I hit a "match may not be exhaustive" warning (and it actually doesn't matched at runtime).

import scala.quoted._

enum TT:
  case T(t: Type[_])

object T {
  def impl[A](t: TT)(using Quotes): Expr[Unit] = {
    t match // match may not be exhaustive
      case TT.T('[x]) =>
        Expr.summon[x]
    '{}
  }
}

Is it supposed to work without _ <: Any constraint? My code uses _ <: AnyKind

[IndiscriminateCoding]

Is it supposed to work without _ <: Any constraint?

I checked and it seems it doesn't :(
Looks like unrelated bug so I've created a separate issue #10864