fix: Closes #18367 -Wconf options are processed incorrectly

[Cherry-picked 16dd58f][modified]

Author: prolativ

compiler/src/dotty/tools/dotc/reporting/WConf.scala

@@ -119,7 +119,7 @@ object WConf:
   def fromSettings(settings: List[String]): Either[List[String], WConf] =
     if (settings.isEmpty) Right(WConf(Nil))
     else
-      val parsedConfs: List[Either[List[String], (List[MessageFilter], Action)]] = settings.map(conf =>
+      val parsedConfs: List[Either[List[String], (List[MessageFilter], Action)]] = settings.reverse.map(conf =>
         val filtersAndAction = conf.split(':')
         if filtersAndAction.length != 2 then Left(List("exactly one `:` expected (<filter>&...&<filter>:<action>)"))
         else

compiler/test/dotty/tools/dotc/config/ScalaSettingsTests.scala

@@ -89,6 +89,7 @@ class ScalaSettingsTests:
     val nowr = new Diagnostic.Warning("This is a problem.".toMessage, util.NoSourcePosition)
     assertEquals(Action.Silent, sut.action(nowr))
 
+<<<<<<< lts-3.3-backport-18503
   @Ignore("LTS backport rejected: https://github.com/scala/scala3/pull/18503")
   @Test def `i18367 rightmost WConf flags take precedence over flags to the left`: Unit =
     import reporting.{Action, Diagnostic}
@@ -199,5 +200,20 @@ class ScalaSettingsTests:
       )
     )
     assertEquals(result, Right(reporting.Action.Error))
+=======
+  @Test def `i18367 rightmost WConf flags take precedence over flags to the left`: Unit =
+    import reporting.{Action, Diagnostic}
+    val sets = new ScalaSettings
+    val args = List("-Wconf:cat=deprecation:e", "-Wconf:cat=deprecation:s")
+    val sumy = ArgsSummary(sets.defaultState, args, errors = Nil, warnings = Nil)
+    val proc = sets.processArguments(sumy, processAll = true, skipped = Nil)
+    val conf = sets.Wconf.valueIn(proc.sstate)
+    val msg  = "Don't use that!".toMessage
+    val depr = new Diagnostic.DeprecationWarning(msg, util.NoSourcePosition)
+    val sut  = reporting.WConf.fromSettings(conf).getOrElse(???)
+    assertEquals(Action.Silent, sut.action(depr))
+
+
+>>>>>>> 16dd58f fix: Closes #18367 `-Wconf` options are processed incorrectly
 
 end ScalaSettingsTests