Unit JS default param makes compiler crash with "Cannot hash a transient IR node"

[armanbilge]

Compiler version

3.2.0-RC1-bin-20220609-2836fbc-NIGHTLY

Minimized code

//> using scala "3.2.0-RC1-bin-20220609-2836fbc-NIGHTLY"
//> using platform "js"

package foo

import scala.scalajs.js

@js.native
trait Bar extends js.Object:
  protected[foo] def baz(
    dummy: Unit = js.native,
  ): Unit = js.native

def bar: Bar = ???

@main def main = bar.baz()

Output

Error: Unexpected error when compiling project_2c44eec9c4_2c44eec9c4-45290ff20c: 'Cannot hash a transient IR node (its value is of class class dotty.tools.backend.sjs.JSCodeGen$UndefinedParam$)'

Expectation

The same code compiles in Scala 2. Woops, I guess not. But the Scala 2 error says:

[error] ./bug.scala:15:1: Found a dangling UndefinedParam at Position(file:/workspace/sandbox/bug.scala,18,17). This is likely due to a bad interaction between a macro or a compiler plugin and the Scala.js compiler plugin. If you hit this, please let us know.

• Unit JS default param makes compiler crash with "Found a dangling UndefinedParam" scala-js/scala-js#4684