Parser crash with an illegal use of `into` modifier

[KacperFKorban]

Compiler version

3.6.1-RC1-bin-20241014-69ac5fb-NIGHTLY

Minimized code

//> using scala 3.nightly
  
into class X

With the language import (import scala.language.experimental.into) also crashes.

Output (click arrow to expand)

  exception occurred while parser /home/kpi/bugs/weirdmods.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: /home/kpi/bugs/weirdmods.scala
        during phase: parser
                mode: Mode(ImplicitsEnabled)
     library version: version 2.13.14
    compiler version: version 3.6.1-RC1-bin-20241014-69ac5fb-NIGHTLY-git-69ac5fb
            settings: -classpath /home/kpi/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala3-library_3/3.6.1-RC1-bin-20241014-69ac5fb-NIGHTLY/scala3-library_3-3.6.1-RC1-bin-20241014-69ac5fb-NIGHTLY.jar:/home/kpi/.cache/coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.14/scala-library-2.13.14.jar -d /home/kpi/bugs/.scala-build/bugs_cef53d4a2d-b5801f736d/classes/main -sourceroot /home/kpi/bugs

Exception in thread "main" scala.MatchError: into (of class dotty.tools.dotc.core.Names$SimpleName)
	at dotty.tools.dotc.parsing.Parsers$Parser.modOfToken(Parsers.scala:3266)
	at dotty.tools.dotc.parsing.Parsers$Parser.addModifier(Parsers.scala:3284)
	at dotty.tools.dotc.parsing.Parsers$Parser.loop$1(Parsers.scala:3345)
	at dotty.tools.dotc.parsing.Parsers$Parser.modifiers(Parsers.scala:3353)
	at dotty.tools.dotc.parsing.Parsers$Parser.defAnnotsMods(Parsers.scala:3388)
	at dotty.tools.dotc.parsing.Parsers$Parser.topStatSeq(Parsers.scala:4554)
	at dotty.tools.dotc.parsing.Parsers$Parser.topstats$1(Parsers.scala:4742)
	at dotty.tools.dotc.parsing.Parsers$Parser.compilationUnit$$anonfun$1(Parsers.scala:4747)
	at dotty.tools.dotc.parsing.Parsers$Parser.checkNoEscapingPlaceholders(Parsers.scala:532)
	at dotty.tools.dotc.parsing.Parsers$Parser.compilationUnit(Parsers.scala:4752)
	at dotty.tools.dotc.parsing.Parsers$Parser.parse(Parsers.scala:205)
	at dotty.tools.dotc.parsing.Parser.parse$$anonfun$1(ParserPhase.scala:32)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at dotty.tools.dotc.core.Phases$Phase.monitor(Phases.scala:507)
	at dotty.tools.dotc.parsing.Parser.parse(ParserPhase.scala:40)
	at dotty.tools.dotc.parsing.Parser.$anonfun$2(ParserPhase.scala:52)
	at scala.collection.Iterator$$anon$6.hasNext(Iterator.scala:479)
	at scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:583)
	at scala.collection.immutable.List.prependedAll(List.scala:152)
	at scala.collection.immutable.List$.from(List.scala:685)
	at scala.collection.immutable.List$.from(List.scala:682)
	at scala.collection.IterableOps$WithFilter.map(Iterable.scala:900)
	at dotty.tools.dotc.parsing.Parser.runOn(ParserPhase.scala:51)
	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:343)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:336)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:384)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:396)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:69)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:396)
	at dotty.tools.dotc.Run.compileSources(Run.scala:282)
	at dotty.tools.dotc.Run.compile(Run.scala:267)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:37)
	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.dotc.Main.main(Main.scala)
Compilation failed

[KacperFKorban]

might be a duplicate/related to #21635

[mbovel]

This issue was picked for the Scala Issue Spree of Monday, November 11th. @KacperFKorban, @hamzaremmal and @kasiaMarek will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.