Fix open-classes.md (#18630)

bishabosha · web-flow · commit 3332943fec34 · 2023-10-02T09:33:56.000+02:00
`-source future` is still required as of 3.3 LTS.
diff --git a/docs/_docs/reference/other-new-features/open-classes.md b/docs/_docs/reference/other-new-features/open-classes.md
@@ -77,4 +77,4 @@ A class that is neither `abstract` nor `open` is similar to a `sealed` class: it
 
 ## Migration
 
-`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source future`. It will be produced by default from Scala 3.1 on.
+`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source future`. It will be produced by default [from Scala 3.4 on](https://github.com/lampepfl/dotty/issues/16334).

Original file line number	Diff line number	Diff line change
@@ -77,4 +77,4 @@ A class that is neither `abstract` nor `open` is similar to a `sealed` class: it
`77`	`77`
`78`	`78`	`## Migration`
`79`	`79`
`80`		-`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source future`. It will be produced by default from Scala 3.1 on.
	`80`	+`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source future`. It will be produced by default [from Scala 3.4 on](https://github.com/lampepfl/dotty/issues/16334).