Some methods with lambda in the name will crash the compiler

[snoble]

reproduction steps

repo with sbt build: https://github.com/snoble/scala-crash

scastie link: https://scastie.scala-lang.org/MywoibUzRSm0Sfb7jGjK8w

using Scala (2.13.1) (reproduced in 2.13.2 and 2.12.11),

Welcome to Scala 2.13.1 (OpenJDK 64-Bit Server VM, Java 1.8.0_252).
Type in expressions for evaluation. Or try :help.

scala> object Crash {
     |   def lambdaList(lst: List[Int]): List[Int] = lst.collect { case n if n > 0 => n }
     | }
error: Error while emitting <console>
assertion failed:
  $read$Crash$$anonfun$lambdaList$1
     while compiling: <console>
        during phase: jvm
     library version: version 2.13.1
    compiler version: version 2.13.1
  reconstructed args: -deprecation -feature

  last tree to typer: Ident(default)
       tree position: line 2 of <console>
            tree tpe: Function1
              symbol: value default
   symbol definition: default: Function1 (a TermSymbol)
      symbol package: $line3
       symbol owners: value default -> method applyOrElse -> <$anon: Function1>
           call site: constructor $read$Crash$$anonfun$lambdaList$1 in package $line3

== Source file context for tree position ==

     1 object Crash {
     2   def lambdaList(lst: List[Int]): List[Int] = lst.collect { case n if n > 0 => n }
     3 }
     4
error: Error while emitting Crash$
assertion failed: $read$Crash$$anonfun$lambdaList$1

problem

it shouldn't error when emitting. Somehow the combination of calling collect and a def that starts with lambda is necessary.

[som-snytt]

It's funnier if you call the method lambdaLift.

➜ ✗ scala -Vdebug
scala> def lambdaList(lst: List[Int]): List[Int] = lst.collect { case n if n > 0 => n }
java.lang.AssertionError: assertion failed: $read$$iw$$anonfun$lambdaList$1
at scala.reflect.internal.SymbolTable.throwAssertionError(SymbolTable.scala:170)
at scala.tools.nsc.backend.jvm.BCodeHelpers.isAnonymousOrLocalClass(BCodeHelpers.scala:86)

where the code comment is

// if some outer name contains $lambda, a non-lambda class is considered lambda.

[som-snytt]

Duplicates #10857 and #2806