I can call $asInstanceOf$

[som-snytt]

Minimized code

Starting dotty REPL...
Dotty compiler version 0.25.0-bin-SNAPSHOT-git-66f335c -- Copyright 2002-2020, LAMP/EPFL
scala> "".$asInstanceOf$[Int]                                                                                          
Caught: dotty.tools.dotc.core.CyclicReference:  while parsing annotations in /modules/java.base/java/lang/annotation/ElementType.class
java.lang.ClassCastException: class java.lang.String cannot be cast to class java.lang.Integer (java.lang.String and java.lang.Integer are in module java.base of loader 'bootstrap')
	at scala.runtime.BoxesRunTime.unboxToInt(BoxesRunTime.java:99)
	at rs$line$1$.<init>(rs$line$1:1)
	at rs$line$1$.<clinit>(rs$line$1)
	at rs$line$1.res0(rs$line$1)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at dotty.tools.repl.Rendering.$anonfun$3(Rendering.scala:72)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.Rendering.valueOf(Rendering.scala:72)
	at dotty.tools.repl.Rendering.renderVal(Rendering.scala:95)
	at dotty.tools.repl.ReplDriver.displayMembers$3$$anonfun$3(ReplDriver.scala:291)
	at scala.collection.immutable.List.map(List.scala:246)
	at scala.collection.immutable.List.map(List.scala:79)
	at dotty.tools.repl.ReplDriver.displayMembers$6(ReplDriver.scala:291)
	at dotty.tools.repl.ReplDriver.displayDefinitions$$anonfun$2(ReplDriver.scala:317)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.ReplDriver.displayDefinitions(ReplDriver.scala:317)
	at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:245)
	at scala.util.Either.fold(Either.scala:189)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:247)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:193)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:127)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:130)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:148)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:130)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)

Output

Exception in thread "main" java.lang.ClassCastException: class java.lang.String cannot be cast to class java.lang.Integer (java.lang.String and java.lang.Integer are in module java.base of loader 'bootstrap')
	at scala.runtime.BoxesRunTime.unboxToInt(BoxesRunTime.java:99)
	at asinstanceof$package$.badinstanceof(asinstanceof.scala:2)
	at badinstanceof.main(asinstanceof.scala:2)

Expectation

Forward port of scala/bug#11843

[odersky]

Names with $ in them are reserved for the compiler's use, and the effects of calling them anyway are undefined. So, don't call them.

[nicolasstucki]

Maybe we should emit a warning when a name with a is parsed $.