Reporter applies lint actions

Instead of testing whether to emit actions by probing suppressions,
just let the reporter apply LintWarning actions when the warning
is actually reported.

Author: som-snytt

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

@@ -40,10 +40,12 @@ object Diagnostic:
    */
   trait OriginWarning(val origin: String):
     self: Warning =>
+  object OriginWarning:
+    val NoOrigin = "..."
 
   /** Lints are likely to be filtered. Provide extra axes for filtering by `-Wconf`.
    */
-  class LintWarning(msg: Message, pos: SourcePosition, origin: String)
+  class LintWarning(msg: Message, pos: SourcePosition, origin: String = OriginWarning.NoOrigin)
   extends Warning(msg, pos), OriginWarning(origin)
 
   class Warning(

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

@@ -9,6 +9,7 @@ import dotty.tools.dotc.core.Mode
 import dotty.tools.dotc.core.Symbols.{NoSymbol, Symbol}
 import dotty.tools.dotc.reporting.Diagnostic.*
 import dotty.tools.dotc.reporting.Message.*
+import dotty.tools.dotc.rewrites.Rewrites
 import dotty.tools.dotc.util.NoSourcePosition
 
 import java.io.{BufferedReader, PrintWriter}
@@ -170,6 +171,8 @@ abstract class Reporter extends interfaces.ReporterResult {
           handleRecursive("error reporting", dia.message, ex)
         dia match {
           case w: Warning =>
+            if w.isInstanceOf[LintWarning] then
+              w.msg.actions.foreach(Rewrites.applyAction)
             warnings = w :: warnings
             _warningCount += 1
           case e: Error   =>

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

@@ -34,7 +34,8 @@ enum MessageFilter:
       pattern.findFirstIn(path).nonEmpty
     case Origin(pattern) =>
       message match
-      case message: OriginWarning => pattern.findFirstIn(message.origin).nonEmpty
+      case message: OriginWarning if message.origin != OriginWarning.NoOrigin =>
+        pattern.findFirstIn(message.origin).nonEmpty
       case _ => false
     case None => false
 

compiler/src/dotty/tools/dotc/transform/CheckUnused.scala

@@ -15,8 +15,8 @@ import dotty.tools.dotc.core.StdNames.nme
 import dotty.tools.dotc.core.Symbols.{ClassSymbol, NoSymbol, Symbol, defn, isDeprecated, requiredClass, requiredModule}
 import dotty.tools.dotc.core.Types.*
 import dotty.tools.dotc.report
-import dotty.tools.dotc.reporting.{Action, CodeAction, Diagnostic, UnusedSymbol, WConf}
-import dotty.tools.dotc.rewrites.Rewrites
+import dotty.tools.dotc.reporting.{CodeAction, Diagnostic, UnusedSymbol}
+import dotty.tools.dotc.rewrites.Rewrites.ActionPatch
 import dotty.tools.dotc.transform.MegaPhase.MiniPhase
 import dotty.tools.dotc.typer.{ImportInfo, Typer}
 import dotty.tools.dotc.typer.Deriving.OriginalTypeClass
@@ -557,29 +557,15 @@ object CheckUnused:
 
   def reportUnused()(using Context): Unit =
     for (msg, pos, origin) <- warnings do
-      if origin.isEmpty then report.warning(msg, pos)
-      else report.warning(msg, pos, origin)
-      // avoid rewrite if warning will be suppressed (would be nice if reporter knew how to apply actions)
-      msg.actions.headOption match
-      case Some(action) if ctx.run != null =>
-        val dia =
-          if origin.isEmpty then Diagnostic.Warning(msg, pos.sourcePos)
-          else Diagnostic.LintWarning(msg, pos.sourcePos, origin)
-        ctx.run.nn.suppressions.nowarnAction(dia) match
-        case Action.Warning =>
-          WConf.parsed.action(dia) match
-          case Action.Error | Action.Warning =>
-            Rewrites.applyAction(action)
-          case _ =>
-        case _ =>
-      case _ =>
+      report.warning(msg, pos, origin)
 
   type MessageInfo = (UnusedSymbol, SrcPos, String) // string is origin or empty
 
   def warnings(using Context): Array[MessageInfo] =
     val actionable = ctx.settings.rewrite.value.nonEmpty
     val warnings = ArrayBuilder.make[MessageInfo]
-    def warnAt(pos: SrcPos)(msg: UnusedSymbol, origin: String = ""): Unit = warnings.addOne((msg, pos, origin))
+    def warnAt(pos: SrcPos)(msg: UnusedSymbol, origin: String = Diagnostic.OriginWarning.NoOrigin): Unit =
+      warnings.addOne((msg, pos, origin))
     val infos = refInfos
 
     // non-local sym was target of assignment or has a sibling setter that was referenced
@@ -742,7 +728,6 @@ object CheckUnused:
 
     def checkImports() =
       import scala.jdk.CollectionConverters.given
-      import Rewrites.ActionPatch
       type ImpSel = (Import, ImportSelector)
       def isUsed(sel: ImportSelector): Boolean = infos.sels.containsKey(sel)
       def warnImport(warnable: ImpSel, actions: List[CodeAction] = Nil): Unit =