Quoted n-ary tuple referring to method params crashes during lambdaLift

[TomasMikula]

Compiler version

3.7.0

Minimized code

macros.scala

import scala.quoted.*

transparent inline def makeAnonFun: (String => Tuple1[String]) =
  ${ makeAnonFunImpl }

// Synthesizes anonymous function
//   (s: String) => s *: EmptyTuple
def makeAnonFunImpl(using Quotes): Expr[String => Tuple1[String]] = {
  import quotes.reflect.*

  val methSym = Symbol.newMethod(
    parent = Symbol.spliceOwner,
    "myMethod",
    MethodType(paramNames = List("s"))(
      mt => List(TypeRepr.of[String]),
      mt => TypeRepr.of[Tuple1[String]]
    )
  )

  val meth = DefDef(
    methSym,
    rhsFn = { case List(args) =>

      // OK: using `Tuple1(...)`
      Some('{ Tuple1(${args(0).asExprOf[String]}) }.asTerm)

      // KO: using `... *: EmptyTuple`
      Some('{ ${args(0).asExprOf[String]} *: EmptyTuple }.asTerm)
    }
  )

  Block(
    List(meth),
    Closure(Ident(methSym.termRef), tpe = None)
  ).asExprOf[String => Tuple1[String]]
}

test.scala

object Test extends App:
  val f = makeAnonFun
  println(f("hi"))

The problem clearly has to do with using the *: syntax, as using Tuple1(...) (or (..., ...) for binary+ tuples) works inside quotes.

Output (click arrow to expand)

error lambda lifting test.scala: value x$1 is not visible from <none>

% scalac macros.scala test.scala
-- [E029] Pattern Match Exhaustivity Warning: macros.scala:22:14 ---------------
22 |    rhsFn = { case List(args) =>
   |              ^
   |              match may not be exhaustive.
   |
   |              It would fail on pattern case: List(_*, _, _*), Nil
   |
   | longer explanation available when compiling with `-explain`
1 warning found
error lambda lifting test.scala: value x$1 is not visible from  <none>

  unhandled exception while running MegaPhase{lambdaLift, elimStaticThis, countOuterAccesses} on test.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Xno-enrich-error-messages.


     while compiling: test.scala
        during phase: MegaPhase{lambdaLift, elimStaticThis, countOuterAccesses}
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.16
    compiler version: version 3.7.0
            settings: 


  Exception while compiling macros.scala, test.scala

  An unhandled exception was thrown in the compiler.
  Please file a crash report here:
  https://github.com/scala/scala3/issues/new/choose
  For non-enriched exceptions, compile with -Xno-enrich-error-messages.


     while compiling: <no file>
        during phase: parser
                mode: Mode()
     library version: version 2.13.16
    compiler version: version 3.7.0
            settings: 

Exception in thread "main" dotty.tools.dotc.transform.Dependencies$NoPath
	at dotty.tools.dotc.transform.Dependencies.markFree(Dependencies.scala:137)
	at dotty.tools.dotc.transform.Dependencies.computeFreeVars$$anonfun$1$$anonfun$1$$anonfun$1$$anonfun$1(Dependencies.scala:283)
	at scala.collection.mutable.LinkedHashSet.foreach(LinkedHashSet.scala:128)
	at dotty.tools.dotc.transform.Dependencies.computeFreeVars$$anonfun$1$$anonfun$1$$anonfun$1(Dependencies.scala:281)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.Option.foreach(Option.scala:437)
	at dotty.tools.dotc.transform.Dependencies.computeFreeVars$$anonfun$1$$anonfun$1(Dependencies.scala:280)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.mutable.LinkedHashSet.foreach(LinkedHashSet.scala:128)
	at dotty.tools.dotc.transform.Dependencies.computeFreeVars$$anonfun$1(Dependencies.scala:279)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.IterableOnceOps.foreach(IterableOnce.scala:619)
	at scala.collection.IterableOnceOps.foreach$(IterableOnce.scala:617)
	at scala.collection.AbstractIterable.foreach(Iterable.scala:935)
	at dotty.tools.dotc.transform.Dependencies.computeFreeVars(Dependencies.scala:278)
	at dotty.tools.dotc.transform.Dependencies.<init>(Dependencies.scala:310)
	at dotty.tools.dotc.transform.LambdaLift$Lifter$$anon$1.<init>(LambdaLift.scala:38)
	at dotty.tools.dotc.transform.LambdaLift$Lifter.<init>(LambdaLift.scala:51)
	at dotty.tools.dotc.transform.LambdaLift.prepareForUnit(LambdaLift.scala:278)
	at dotty.tools.dotc.transform.MegaPhase.prepUnit(MegaPhase.scala:1107)
	at dotty.tools.dotc.transform.MegaPhase.transformUnit(MegaPhase.scala:480)
	at dotty.tools.dotc.transform.MegaPhase.run(MegaPhase.scala:493)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:383)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:334)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:376)
	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:367)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1324)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:360)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$2(Run.scala:407)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1$$anonfun$adapted$1(Run.scala:407)
	at scala.Function0.apply$mcV$sp(Function0.scala:42)
	at dotty.tools.dotc.Run.showProgress(Run.scala:469)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:407)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:419)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:419)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:312)
	at dotty.tools.dotc.Run.compileSuspendedUnits(Run.scala:433)
	at dotty.tools.dotc.Driver.finish(Driver.scala:63)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:38)
	at dotty.tools.dotc.Driver.process(Driver.scala:201)
	at dotty.tools.dotc.Driver.process(Driver.scala:169)
	at dotty.tools.dotc.Driver.process(Driver.scala:181)
	at dotty.tools.dotc.Driver.main(Driver.scala:211)
	at dotty.tools.MainGenericCompiler$.run$1(MainGenericCompiler.scala:162)
	at dotty.tools.MainGenericCompiler$.main(MainGenericCompiler.scala:186)
	at dotty.tools.MainGenericCompiler.main(MainGenericCompiler.scala)