Warn dubious settings

Author: som-snytt

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

@@ -4,6 +4,7 @@ package config
 import Settings.*
 import core.Contexts.*
 import printing.Highlighting
+import reporting.NoExplanation
 
 import dotty.tools.dotc.util.chaining.*
 import scala.PartialFunction.cond
@@ -125,7 +126,8 @@ trait CliCommand:
    */
   def checkUsage(summary: ArgsSummary, sourcesRequired: Boolean)(using settings: ConcreteSettings)(using SettingsState, Context): Option[List[String]] =
     // Print all warnings encountered during arguments parsing
-    summary.warnings.foreach(report.warning(_))
+    for warning <- summary.warnings; message = NoExplanation(warning) do
+      report.configurationWarning(message)
 
     if summary.errors.nonEmpty then
       summary.errors foreach (report.error(_))

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

@@ -20,6 +20,9 @@ object report:
   private def issueWarning(warning: Warning)(using Context): Unit =
     ctx.reporter.report(warning)
 
+  def configurationWarning(msg: Message, pos: SrcPos = NoSourcePosition)(using Context): Unit =
+    issueWarning(ConfigurationWarning(msg, pos.sourcePos))
+
   def deprecationWarning(msg: Message, pos: SrcPos, origin: String = "")(using Context): Unit =
     issueWarning(DeprecationWarning(msg, addInlineds(pos), origin))
 

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

@@ -87,6 +87,10 @@ object Diagnostic:
   extends ConditionalWarning(msg, pos), OriginWarning(origin):
     def enablingOption(using Context): Setting[Boolean] = ctx.settings.deprecation
 
+  class ConfigurationWarning(msg: Message, pos: SourcePosition) extends ConditionalWarning(msg, pos):
+    def enablingOption(using Context): Setting[Boolean] = Setting.internal("-configuration", value = true)
+    override def isSummarizedConditional(using Context): Boolean = false
+
   class MigrationWarning(
     msg: Message,
     pos: SourcePosition

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

@@ -13,7 +13,7 @@ import dotty.tools.dotc.util.NoSourcePosition
 
 import java.io.{BufferedReader, PrintWriter}
 import scala.annotation.internal.sharable
-import scala.collection.mutable
+import scala.collection.mutable.ListBuffer
 import core.Decorators.{em, toMessage}
 import core.handleRecursive
 
@@ -228,14 +228,13 @@ abstract class Reporter extends interfaces.ReporterResult {
       report(new Error("No warnings can be incurred under -Werror (or -Xfatal-warnings)", NoSourcePosition))
 
   /** Summary of warnings and errors */
-  def summary: String = {
-    val b = new mutable.ListBuffer[String]
+  def summary: String =
+    val b = ListBuffer.empty[String]
     if (warningCount > 0)
       b += countString(warningCount, "warning") + " found"
     if (errorCount > 0)
       b += countString(errorCount, "error") + " found"
     b.mkString("\n")
-  }
 
   def summarizeUnreportedWarnings()(using Context): Unit =
     for (settingName, count) <- unreportedWarnings do
@@ -246,7 +245,7 @@ abstract class Reporter extends interfaces.ReporterResult {
   /** Print the summary of warnings and errors */
   def printSummary()(using Context): Unit =
     val s = summary
-    if (s != "") doReport(Warning(s.toMessage, NoSourcePosition))
+    if !s.isEmpty then doReport(Warning(s.toMessage, NoSourcePosition))
 
   /** Returns a string meaning "n elements". */
   protected def countString(n: Int, elements: String): String = n match {

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

@@ -19,12 +19,13 @@ enum MessageFilter:
     import Diagnostic.*
     this match
     case Any => true
+    case Configuration => message.isInstanceOf[ConfigurationWarning]
     case Deprecated => message.isInstanceOf[DeprecationWarning]
     case Feature => message.isInstanceOf[FeatureWarning]
     case Unchecked => message.isInstanceOf[UncheckedWarning]
     case MessageID(errorId) => message.msg.errorId == errorId
     case MessagePattern(pattern) =>
-      val noHighlight = message.msg.message.replaceAll("\\e\\[[\\d;]*[^\\d;]","")
+      val noHighlight = message.msg.message.replaceAll("\\e\\[[\\d;]*[^\\d;]", "")
       pattern.findFirstIn(noHighlight).nonEmpty
     case SourcePattern(pattern) =>
       val source = message.position.orElse(NoSourcePosition).source()
@@ -38,7 +39,7 @@ enum MessageFilter:
       case _ => false
     case None => false
 
-  case Any, Deprecated, Feature, Unchecked, None
+  case Any, Configuration, Deprecated, Feature, Unchecked, None
   case MessagePattern(pattern: Regex)
   case MessageID(errorId: ErrorMessageID)
   case SourcePattern(pattern: Regex)
@@ -97,6 +98,7 @@ object WConf:
         catch case _: IllegalArgumentException => Left(s"unknown error message name: $conf")
 
       case "cat" => conf match
+        case "configuration" => Right(Configuration)
         case "deprecation" => Right(Deprecated)
         case "feature"     => Right(Feature)
         case "unchecked"   => Right(Unchecked)