Extension method on Java class fails in runtime

[prolativ]

Compiler version

3.0.0

Minimized code

String.nn

Output (click arrow to expand)

Exception in thread "main" java.lang.NoClassDefFoundError: java/lang/String$
	at java.lang.Class.getDeclaredMethods0(Native Method)
	at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
	at java.lang.Class.getDeclaredMethods(Class.java:1975)
	at dotty.tools.repl.Rendering.valueOf(Rendering.scala:102)
	at dotty.tools.repl.Rendering.renderVal(Rendering.scala:141)
	at dotty.tools.repl.ReplDriver.$anonfun$13(ReplDriver.scala:323)
	at scala.collection.immutable.List.flatMap(List.scala:293)
	at scala.collection.immutable.List.flatMap(List.scala:79)
	at dotty.tools.repl.ReplDriver.extractAndFormatMembers$1(ReplDriver.scala:323)
	at dotty.tools.repl.ReplDriver.renderDefinitions$$anonfun$2(ReplDriver.scala:346)
	at scala.Option.map(Option.scala:242)
	at dotty.tools.repl.ReplDriver.renderDefinitions(ReplDriver.scala:349)
	at dotty.tools.repl.ReplDriver.compile$$anonfun$2(ReplDriver.scala:268)
	at scala.util.Either.fold(Either.scala:189)
	at dotty.tools.repl.ReplDriver.compile(ReplDriver.scala:285)
	at dotty.tools.repl.ReplDriver.interpret(ReplDriver.scala:212)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:145)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:148)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:167)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:148)
	at dotty.tools.repl.ReplDriver.tryRunning(ReplDriver.scala:114)
	at dotty.tools.repl.Main$.main(Main.scala:6)
	at dotty.tools.repl.Main.main(Main.scala)
Caused by: java.lang.ClassNotFoundException: java.lang.String$
	at dotty.tools.repl.AbstractFileClassLoader.findClass$$anonfun$1(AbstractFileClassLoader.scala:44)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.repl.AbstractFileClassLoader.findClass(AbstractFileClassLoader.scala:46)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
	at dotty.tools.repl.AbstractFileClassLoader.loadClass(AbstractFileClassLoader.scala:55)
	... 23 more

Expectation

This should not throw an exception.

[OlivierBlanvillain]

Minimized (without inline):

extension [T](x: T) def ext: T = x
def foo = String.ext

FWIW -Ycheck:all catches the anomaly after erasure:

*** error while checking /home/olivier/workspace/dotty/tests/run/12537.scala after phase erasure ***                         
exception occurred while compiling /home/olivier/workspace/dotty/tests/run/12537.scala                                       
Exception in thread "main" java.lang.AssertionError: assertion failed: Java class can't be used as value: Ident(String)

[griggt]

Same stack trace as #12346

[bishabosha]

seems like an implicit conversion/extension should never be applied to a module if it is java defined