-Wconf:msg doesn't work as in scala2

[Daenyth]

Compiler version

3.3.1

Minimized code

Could be anything, but I was testing with the example code from scalatest:

https://scastie.scala-lang.org/MlixqluOSei8PhRAqT69aw

Output

It fails to compile with unused value of type org.scalatest.Assertion

Expectation

The same exact code+sbt configuration works in scala 2.13, compiling without error

https://scastie.scala-lang.org/Bdz9lvvrT6y84XverBCfCA

The output of -Wconf:help on scala 3.3.1 suggests that this should work:

<filter>

• Message content: msg=regex
  The regex need only match some part of the message, not all of it.

<action>

• silent / s

[som-snytt]

Probably related to #18829

A simple example works, so probably a combination of macro expansion and premature erroring. It should emit configured messaging at the end of the run.

"Simple example":

➜  ~/projects/dotty/bin/scalac '-Wconf:msg=unused value of type C:s' -Wunused:all -Wnonunit-statement -d /tmp/sandbox simple-unused.scala
➜  cat simple-unused.scala

case class C(c: Int)

object X:
  C(79)

[caoilte]

The problem appears to be the "-Xfatal-warnings" flag rather than any problem with the -W:conf settings.

I was able to make the scastie work by removing fatal warnings. Conversely I wasn't able to find any -W:conf setting that worked (including -Wconf:any:s) with fatal warnings turned on.

[som-snytt]

@caoilte the PR I linked above now links to the fix for #18634 on 3.4.1

[Daenyth]

Can this be backported to 3.3.x?