Please give a try to the new release candidate and let us know if anything regressed before the final release.
The stable release for 3.8.4 is planned no earlier then April 30. We recommend to try out the new RC version during this period and report any found problems in this thread or in dedicated issue on Scala 3 issues tracker. Bugs reported early during the RC period have a higher chance to be fixed and backported to the stable release!
Second RC is now available for tests!
Traces in macrsexperimental.safe mode3.8.4-RC3 is now available for testing!
This release beside upgrades of scala-cli, contains multiple fixes to issues found during recent security audit of the compiler and standard library.
Stable release planned for the next week
Scala 3.8.4 is now out!
@WojciechMazur
When I start the REPL I get this warning:
$ scala
Jun 08, 2026 5:39:21 PM org.jline.utils.Log logr
WARNING: The Parser of class dotty.tools.repl.JLineTerminal$$anon$2 does not support the CompletingParsedLine interface. Completion with escaped or quoted words won't work correctly.
Welcome to Scala 3.8.4 (21.0.5, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala>
I guess it is a known problem?
And also I wonder how to get help in REPL on options as promissed? (Or maybe I missed something, but the release blog doesn’t say how)
scala> :help -Wconf
The REPL has several commands available:
:help print this summary
:load <path> interpret lines in a file
:quit exit the interpreter
:type <expression> evaluate the type of the given expression
:doc <expression> print the documentation for the given expression
:imports show import history
:reset [options] reset the repl to its initial state, forgetting all session entries
:settings <options> update compiler options, if possible
:silent disable/enable automatic printing of results
:dep <group>::<artifact>:<version> Resolve a dependency and make it available in the REPL
Right, we must have missed the backport. It should be fixed in the 3.9.0-RC1 already
In REPL it should be usable under :settings, eg
scala> :settings -Wconf:help
-Wconf Configure compiler warnings.
scala> :settings -Wunused:help
-Wunused Enable or disable specific `unused` warnings
Choices:
- nowarn,
- all,
- imports :
Warn if an import selector is not referenced.,
- privates :
Warn if a private member is unused,
- locals :
Warn if a local definition is unused,
- explicits :
Warn if an explicit parameter is unused,
- implicits :
Warn if an implicit parameter is unused,
- params :
Enable -Wunused:explicits,implicits,
- patvars :
Warn if a variable bound in a pattern is unused,
- linted :
Enable -Wunused:imports,privates,locals,implicits
I can actually spot some additional regression, because under 3.8.3 -Wconf alone printed longer help message and -X:help now crashes… Opened an issue for these Regressions for help messages under `:help` · Issue #26276 · scala/scala3 · GitHub
Anyway, my own typical use was usage from runner, eg.:
❯ scala test.scala -Wunused:help
Compiling project (Scala 3.8.4, JVM (17))
-Wunused Enable or disable specific `unused` warnings
Choices:
- nowarn,
- all,
....
Perhaps update the blog post with an example of how to use help for options? As it reads now it looks like you should start with :help … Also the text printed when typing “:help” could give some hints on how to use settings-help perhaps, to make it more discoverable?