Warn instead of fail for invalid -Xlint args

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -35,7 +35,7 @@ class Compiler {
   protected def frontendPhases: List[List[Phase]] =
     List(new Parser) ::             // Compiler frontend: scanner, parser
     List(new TyperPhase) ::         // Compiler frontend: namer, typer
-    List(new CheckShadowing, new CheckUnused.PostTyper) ::  // Check for unused elements // Check for shadowing elements
+    List(new CheckUnused.PostTyper, new CheckShadowing) :: // Check for unused elements and shadowing elements
     List(new YCheckPositions) ::    // YCheck positions
     List(new sbt.ExtractDependencies) :: // Sends information on classes' dependencies to sbt via callbacks
     List(new semanticdb.ExtractSemanticDB) :: // Extract info into .semanticdb files

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -307,7 +307,7 @@ private sealed trait XSettings:
 
   val XmacroSettings: Setting[List[String]] = MultiStringSetting("-Xmacro-settings", "setting1,setting2,..settingN", "List of settings which exposed to the macros")
 
-  val Xlint: Setting[List[ChoiceWithHelp[String]]] = MultiChoiceHelpSetting(
+  val Xlint: Setting[List[ChoiceWithHelp[String]]] = UncompleteMultiChoiceHelpSetting(
     name = "-Xlint",
     helpArg = "advanced warning",
     descr = "Enable or disable specific `lint` warnings",

compiler/src/dotty/tools/dotc/config/Settings.scala

@@ -62,6 +62,7 @@ object Settings:
     prefix: String = "",
     aliases: List[String] = Nil,
     depends: List[(Setting[?], Any)] = Nil,
+    ignoreInvalidArgs: Boolean = false,
     propertyClass: Option[Class[?]] = None)(private[Settings] val idx: Int) {
 
     private var changed: Boolean = false
@@ -104,8 +105,16 @@ object Settings:
       def fail(msg: String, args: List[String]) =
         ArgsSummary(sstate, args, errors :+ msg, warnings)
 
+      def warn(msg: String, args: List[String]) =
+        ArgsSummary(sstate, args, errors, warnings :+ msg)
+
       def missingArg =
-        fail(s"missing argument for option $name", args)
+        val msg = s"missing argument for option $name"
+        if ignoreInvalidArgs then warn(msg + ", the tag was ignored", args)  else fail(msg, args)
+
+      def invalidChoices(invalid: List[String]) =
+        val msg = s"invalid choice(s) for $name: ${invalid.mkString(",")}"
+        if ignoreInvalidArgs then warn(msg + ", the tag was ignored", args) else fail(msg, args)
 
       def setBoolean(argValue: String, args: List[String]) =
         if argValue.equalsIgnoreCase("true") || argValue.isEmpty then update(true, args)
@@ -144,7 +153,7 @@ object Settings:
             choices match
               case Some(valid) => strings.filterNot(valid.contains) match
                 case Nil => update(strings, args)
-                case invalid => fail(s"invalid choice(s) for $name: ${invalid.mkString(",")}", args)
+                case invalid => invalidChoices(invalid)
               case _ => update(strings, args)
         case (StringTag, _) if argRest.nonEmpty || choices.exists(_.contains("")) =>
           setString(argRest, args)
@@ -287,6 +296,9 @@ object Settings:
     def MultiChoiceHelpSetting(name: String, helpArg: String, descr: String, choices: List[ChoiceWithHelp[String]], default: List[ChoiceWithHelp[String]], aliases: List[String] = Nil): Setting[List[ChoiceWithHelp[String]]] =
       publish(Setting(name, descr, default, helpArg, Some(choices), aliases = aliases))
 
+    def UncompleteMultiChoiceHelpSetting(name: String, helpArg: String, descr: String, choices: List[ChoiceWithHelp[String]], default: List[ChoiceWithHelp[String]], aliases: List[String] = Nil): Setting[List[ChoiceWithHelp[String]]] =
+      publish(Setting(name, descr, default, helpArg, Some(choices), aliases = aliases, ignoreInvalidArgs = true))
+
     def IntSetting(name: String, descr: String, default: Int, aliases: List[String] = Nil): Setting[Int] =
       publish(Setting(name, descr, default, aliases = aliases))
 

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

@@ -83,7 +83,7 @@ class CheckShadowing extends MiniPhase:
     ctx
 
   override def prepareForOther(tree: tpd.Tree)(using Context): Context =
-    importTraverser(tree.symbol).traverse(tree)
+    importTraverser.traverse(tree)
     ctx
 
   override def prepareForValDef(tree: tpd.ValDef)(using Context): Context =
@@ -152,7 +152,7 @@ class CheckShadowing extends MiniPhase:
   end nestedTypeTraverser
 
   // To reach the imports during a miniphase traversal
-  private def importTraverser(parent: Symbol) = new TreeTraverser:
+  private def importTraverser = new TreeTraverser:
     import tpd._
 
     override def traverse(tree: tpd.Tree)(using Context): Unit =

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

@@ -291,9 +291,9 @@ class CheckUnused private (phaseMode: CheckUnused.PhaseMode, suffix: String, _ke
         case UnusedSymbol(t, _, WarnTypes.PatVars) =>
           report.warning(s"unused pattern variable", t)
         case UnusedSymbol(t, _, WarnTypes.UnsetLocals) =>
-          report.warning(s"unset local variable", t)
+          report.warning(s"unset local variable, consider using an immutable val instead", t)
         case UnusedSymbol(t, _, WarnTypes.UnsetPrivates) =>
-          report.warning(s"unset private variable", t)
+          report.warning(s"unset private variable, consider using an immutable val instead", t)
     }
 
 end CheckUnused