latest 2.13.x compiler crash with "val `_` = 42"

[xuwei-k]

build.sbt

resolvers += "scala-pr" at "https://scala-ci.typesafe.com/artifactory/scala-integration/"

scalaVersion := "2.13.0-pre-9e26448"

A.scala

package example

class A {
  val `_` = 42
}

[info] Compiling 1 Scala source to /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes ...
exception when typing <_: error>.==(x1)/class scala.reflect.internal.Trees$Apply
not found: value _ in file /Users/kenji/xuwei-k/scala-latest/A.scala
scala.reflect.internal.Types$TypeError: not found: value _
[error] 
[error]   unrecoverable error
[error]      while compiling: /Users/kenji/xuwei-k/scala-latest/A.scala
[error]         during phase: globalPhase=erasure, enteringPhase=posterasure
[error]      library version: version 2.13.0-pre-9e26448
[error]     compiler version: version 2.13.0-pre-9e26448
[error]   reconstructed args: -bootclasspath /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/classes:/Users/kenji/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.13.0-pre-9e26448.jar -classpath /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes
[error] 
[error]   last tree to typer: Ident(x)
[error]        tree position: line 4 of /Users/kenji/xuwei-k/scala-latest/A.scala
[error]               symbol: value x
[error]    symbol definition: x: scala.runtime.BoxedUnit (a TermSymbol)
[error]       symbol package: <none>
[error]        symbol owners: value x
[error]            call site: class A in package example in package example
[error] 
[error] == Source file context for tree position ==
[error] 
[error]      1 package example
[error]      2 
[error]      3 class A {
[error]      4   val `_` = 42
[error]      5 }
[error]      6 
exception when typing if (<_: error>.==(x1))
  matchEnd4(())
else
  case6()
exception when typing case5(){
  if (<_: error>.==(x1))
    matchEnd4(())
  else
    case6()
}
exception when typing {
  case <synthetic> val x1: Int = (42: Int(42));
  case5(){
    if (<_: error>.==(x1))
      matchEnd4(())
    else
      case6()
  };
  case6(){
    matchEnd4(throw new MatchError(x1))
  };
  matchEnd4(x){
    x
  }
}
exception when typing <synthetic> <artifact> private[this] val x$1: scala.runtime.BoxedUnit = {
  case <synthetic> val x1: Int = (42: Int(42));
  case5(){
    if (<_: error>.==(x1))
      matchEnd4(())
    else
      case6()
  };
  case6(){
    matchEnd4(throw new MatchError(x1))
  };
  matchEnd4(x){
    x
  }
}
exception when typing class A extends Object {
  def <init>(): example.A = {
    A.super.<init>();
    ()
  };
  <synthetic> <artifact> private[this] val x$1: scala.runtime.BoxedUnit = {
    case <synthetic> val x1: Int = (42: Int(42));
    case5(){
      if (<_: error>.==(x1))
        matchEnd4(())
      else
        case6()
    };
    case6(){
      matchEnd4(throw new MatchError(x1))
    };
    matchEnd4(x){
      x
    }
  }
}
exception when typing package example {
  class A extends Object {
    def <init>(): example.A = {
      A.super.<init>();
      ()
    };
    <synthetic> <artifact> private[this] val x$1: scala.runtime.BoxedUnit = {
      case <synthetic> val x1: Int = (42: Int(42));
      case5(){
        if (<_: error>.==(x1))
          matchEnd4(())
        else
          case6()
      };
      case6(){
        matchEnd4(throw new MatchError(x1))
      };
      matchEnd4(x){
        x
      }
    }
  }
}
[error] ## Exception when compiling 1 sources to /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes
[error] 
[error]   unrecoverable error
[error]      while compiling: /Users/kenji/xuwei-k/scala-latest/A.scala
[error]         during phase: globalPhase=erasure, enteringPhase=posterasure
[error]      library version: version 2.13.0-pre-9e26448
[error]     compiler version: version 2.13.0-pre-9e26448
[error]   reconstructed args: -bootclasspath /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/classes:/Users/kenji/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.13.0-pre-9e26448.jar -classpath /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes
[error] 
[error]   last tree to typer: Ident(x)
[error]        tree position: line 4 of /Users/kenji/xuwei-k/scala-latest/A.scala
[error]               symbol: value x
[error]    symbol definition: x: scala.runtime.BoxedUnit (a TermSymbol)
[error]       symbol package: <none>
[error]        symbol owners: value x
[error]            call site: class A in package example in package example
[error] 
[error] == Source file context for tree position ==
[error] 
[error]      1 package example
[error]      2 
[error]      3 class A {
[error]      4   val `_` = 42
[error]      5 }
[error]      6 
[error] scala.reflect.internal.Reporting.abort(Reporting.scala:68)
[error] scala.reflect.internal.Reporting.abort$(Reporting.scala:64)
[error] scala.reflect.internal.SymbolTable.abort(SymbolTable.scala:26)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:804)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedIf$1(Typers.scala:5804)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5670)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedLabelDef(Typers.scala:5815)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5685)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:2444)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5669)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedValDefImpl(Typers.scala:5995)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedValDef(Typers.scala:2007)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5648)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1960)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedClassDef(Typers.scala:1799)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5650)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] scala.tools.nsc.typechecker.Typers$Typer.typedPackageDef$1(Typers.scala:5350)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5653)
[error] scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] scala.tools.nsc.transform.Erasure$ErasureTransformer.$anonfun$transform$2(Erasure.scala:1371)
[error] scala.tools.nsc.transform.Erasure$ErasureTransformer.transform(Erasure.scala:1371)
[error] scala.tools.nsc.ast.Trees$Transformer.transformUnit(Trees.scala:162)
[error] scala.tools.nsc.transform.Transform$Phase.apply(Transform.scala:37)
[error] scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:447)
[error] scala.tools.nsc.Global$GlobalPhase.run(Global.scala:398)
[error] scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1480)
[error] scala.tools.nsc.Global$Run.compileUnits(Global.scala:1464)
[error] scala.tools.nsc.Global$Run.compileSources(Global.scala:1456)
[error] scala.tools.nsc.Global$Run.compile(Global.scala:1580)
[error] xsbt.CachedCompiler0.run(CompilerInterface.scala:130)
[error] xsbt.CachedCompiler0.run(CompilerInterface.scala:105)
[error] xsbt.CompilerInterface.run(CompilerInterface.scala:31)
[error] sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] java.lang.reflect.Method.invoke(Method.java:498)
[error] sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:237)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:111)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:90)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:133)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:73)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:116)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:307)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:307)
[error] sbt.internal.inc.Incremental$.doCompile(Incremental.scala:106)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:87)
[error] sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:116)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:63)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:89)
[error] sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:134)
[error] sbt.internal.inc.Incremental$.compile(Incremental.scala:80)
[error] sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:67)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:311)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:269)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:159)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:238)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:69)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1549)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1523)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:40)
[error] sbt.std.Transform$$anon$4.work(System.scala:67)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:269)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] sbt.Execute.work(Execute.scala:278)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:269)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.Executors$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] scala.reflect.internal.FatalError: 
[error]   unrecoverable error
[error]      while compiling: /Users/kenji/xuwei-k/scala-latest/A.scala
[error]         during phase: globalPhase=erasure, enteringPhase=posterasure
[error]      library version: version 2.13.0-pre-9e26448
[error]     compiler version: version 2.13.0-pre-9e26448
[error]   reconstructed args: -bootclasspath /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/classes:/Users/kenji/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.13.0-pre-9e26448.jar -classpath /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes
[error] 
[error]   last tree to typer: Ident(x)
[error]        tree position: line 4 of /Users/kenji/xuwei-k/scala-latest/A.scala
[error]               symbol: value x
[error]    symbol definition: x: scala.runtime.BoxedUnit (a TermSymbol)
[error]       symbol package: <none>
[error]        symbol owners: value x
[error]            call site: class A in package example in package example
[error] 
[error] == Source file context for tree position ==
[error] 
[error]      1 package example
[error]      2 
[error]      3 class A {
[error]      4   val `_` = 42
[error]      5 }
[error]      6 
[error] 	at scala.reflect.internal.Reporting.abort(Reporting.scala:68)
[error] 	at scala.reflect.internal.Reporting.abort$(Reporting.scala:64)
[error] 	at scala.reflect.internal.SymbolTable.abort(SymbolTable.scala:26)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:804)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedIf$1(Typers.scala:5804)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5670)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedLabelDef(Typers.scala:5815)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5685)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedBlock(Typers.scala:2444)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedOutsidePatternMode$1(Typers.scala:5669)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5704)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedValDefImpl(Typers.scala:5995)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedValDef(Typers.scala:2007)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5648)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1960)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedClassDef(Typers.scala:1799)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5650)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStat$1(Typers.scala:5804)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.$anonfun$typedStats$10(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3300)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typedPackageDef$1(Typers.scala:5350)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5653)
[error] 	at scala.tools.nsc.transform.Erasure$Eraser.typed1(Erasure.scala:797)
[error] 	at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5740)
[error] 	at scala.tools.nsc.transform.Erasure$ErasureTransformer.$anonfun$transform$2(Erasure.scala:1371)
[error] 	at scala.tools.nsc.transform.Erasure$ErasureTransformer.transform(Erasure.scala:1371)
[error] 	at scala.tools.nsc.ast.Trees$Transformer.transformUnit(Trees.scala:162)
[error] 	at scala.tools.nsc.transform.Transform$Phase.apply(Transform.scala:37)
[error] 	at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:447)
[error] 	at scala.tools.nsc.Global$GlobalPhase.run(Global.scala:398)
[error] 	at scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1480)
[error] 	at scala.tools.nsc.Global$Run.compileUnits(Global.scala:1464)
[error] 	at scala.tools.nsc.Global$Run.compileSources(Global.scala:1456)
[error] 	at scala.tools.nsc.Global$Run.compile(Global.scala:1580)
[error] 	at xsbt.CachedCompiler0.run(CompilerInterface.scala:130)
[error] 	at xsbt.CachedCompiler0.run(CompilerInterface.scala:105)
[error] 	at xsbt.CompilerInterface.run(CompilerInterface.scala:31)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] 	at sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:237)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:111)
[error] 	at sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:90)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
[error] 	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:133)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:73)
[error] 	at sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:116)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:307)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:307)
[error] 	at sbt.internal.inc.Incremental$.doCompile(Incremental.scala:106)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:87)
[error] 	at sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:116)
[error] 	at sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:63)
[error] 	at sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:89)
[error] 	at sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:134)
[error] 	at sbt.internal.inc.Incremental$.compile(Incremental.scala:80)
[error] 	at sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:67)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:311)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:269)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:159)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:238)
[error] 	at sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:69)
[error] 	at sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1549)
[error] 	at sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1523)
[error] 	at scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] 	at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:40)
[error] 	at sbt.std.Transform$$anon$4.work(System.scala:67)
[error] 	at sbt.Execute.$anonfun$submit$2(Execute.scala:269)
[error] 	at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] 	at sbt.Execute.work(Execute.scala:278)
[error] 	at sbt.Execute.$anonfun$submit$1(Execute.scala:269)
[error] 	at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:178)
[error] 	at sbt.CompletionService$$anon$2.call(CompletionService.scala:37)
[error] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] 	at java.lang.Thread.run(Thread.java:748)
[error] (Compile / compileIncremental) scala.reflect.internal.FatalError: 
[error]   unrecoverable error
[error]      while compiling: /Users/kenji/xuwei-k/scala-latest/A.scala
[error]         during phase: globalPhase=erasure, enteringPhase=posterasure
[error]      library version: version 2.13.0-pre-9e26448
[error]     compiler version: version 2.13.0-pre-9e26448
[error]   reconstructed args: -bootclasspath /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/sunrsasign.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home/jre/classes:/Users/kenji/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.13.0-pre-9e26448.jar -classpath /Users/kenji/xuwei-k/scala-latest/target/scala-2.13.0-pre-9e26448/classes
[error] 
[error]   last tree to typer: Ident(x)
[error]        tree position: line 4 of /Users/kenji/xuwei-k/scala-latest/A.scala
[error]               symbol: value x
[error]    symbol definition: x: scala.runtime.BoxedUnit (a TermSymbol)
[error]       symbol package: <none>
[error]        symbol owners: value x
[error]            call site: class A in package example in package example
[error] 
[error] == Source file context for tree position ==
[error] 
[error]      1 package example
[error]      2 
[error]      3 class A {
[error]      4   val `_` = 42
[error]      5 }
[error]      6 
[error] Total time: 0 s, completed Jan 21, 2019 3:24:06 PM

[szeiger]

Related issues: #10384 #7691

[som-snytt]

I broke this for 7691, fix attached, but the following is already broken on 2.12 with the same failure:

val Some(`_`) = Option(42)

Edit: fixed the second symptom on the ticket, though it's probably throwaway code no one will exercise except Jenkins and @xuwei-k

(10384 is surely the correct fix, perhaps allowing backticked reference to Java members.)