Make Spec classes open

[wasowski]

Starting Scala 3.1 (AFAIK) the compiler produces a warning (and under some settings an error) whenever extending a class that is not declared as open. Having studied https://docs.scala-lang.org/scala3/reference/other-new-features/open-classes.html, it seems to me that spec super classes are clear use case for open classes. Is there any reason why they are not declared open?

The warning message for the record, and for Google:

[warn] -- Feature Warning: [...] .scala:8:25
[warn] 8 |  org.scalatest.freespec.AnyFreeSpec,
[warn]   |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[warn]   |Unless class AnyFreeSpec is declared 'open', its extension in a separate file should be enabled
[warn]   |by adding the import clause 'import scala.language.adhocExtensions'
[warn]   |or by setting the compiler option -language:adhocExtensions.
[warn]   |See the Scala docs for value scala.language.adhocExtensions for a discussion
[warn]   |why the feature should be explicitly enabled.
[warn] one warning found

[cheeseng]

@wasowski I agree, they are good candidates for Scala 3 open class. I have submitted the following PR here:

#2146

[wasowski]

This appears to be merged (and I no longer get this error on 3.2.14).