crash with compilable code: "java.lang.IllegalArgumentException: requirement failed"

[helloqirun]

scalac can compile but dotc crashes.

$ cat abc.scala

class foo(annotation: Any) extends annotation.StaticAnnotation
@foo(new AnyRef {}) trait A

$ dotc abc.scala

-- [E008] Member Not Found Error: abc.scala ------------------------------------
1 |class foo(annotation: Any) extends annotation.StaticAnnotation
  |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |                type `StaticAnnotation` is not a member of Any(annotation)

exception occurred while typechecking abc.scala

exception occurred while compiling abc.scala
Exception in thread "main" java.lang.IllegalArgumentException: requirement failed
	at scala.Predef$.require(Predef.scala:207)
	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.enterNoReplace(SymDenotations.scala:1538)
	at dotty.tools.dotc.core.SymDenotations$ClassDenotation.enter(SymDenotations.scala:1528)
	at dotty.tools.dotc.typer.NamerContextOps$class.enter(Namer.scala:36)
	at dotty.tools.dotc.core.Contexts$Context.enter(Contexts.scala:57)
	at dotty.tools.dotc.typer.Namer.enterSymbol(Namer.scala:339)
	at dotty.tools.dotc.typer.Namer.dotty$tools$dotc$typer$Namer$$recur$1(Namer.scala:437)
<snipped>

[odersky]

This also does the trick:

class foo(annotation: Any)
@foo(new AnyRef {}) trait A

The problem is a double definition of the class $anon that's defined in the new AnyRef {} argument. It seems to come up if foo is not an annotation.

[smarter]

Already fixed, regression test in #5800.