Support -Wconf and @nowarn

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

@@ -16,7 +16,9 @@ import io.{AbstractFile, PlainFile, VirtualFile}
 import Phases.unfusedPhases
 
 import util._
-import reporting.Reporter
+import reporting.{Reporter, Suppression, Action}
+import reporting.Diagnostic
+import reporting.Diagnostic.Warning
 import rewrites.Rewrites
 
 import profile.Profiler
@@ -96,6 +98,60 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
   private var myUnitsCached: List[CompilationUnit] = _
   private var myFiles: Set[AbstractFile] = _
 
+  // `@nowarn` annotations by source file, populated during typer
+  private val mySuppressions: mutable.LinkedHashMap[SourceFile, mutable.ListBuffer[Suppression]] = mutable.LinkedHashMap.empty
+  // source files whose `@nowarn` annotations are processed
+  private val mySuppressionsComplete: mutable.Set[SourceFile] = mutable.Set.empty
+  // warnings issued before a source file's `@nowarn` annotations are processed, suspended so that `@nowarn` can filter them
+  private val mySuspendedMessages: mutable.LinkedHashMap[SourceFile, mutable.LinkedHashSet[Warning]] = mutable.LinkedHashMap.empty
+
+  object suppressions:
+    // When the REPL creates a new run (ReplDriver.compile), parsing is already done in the old context, with the
+    // previous Run. Parser warnings were suspended in the old run and need to be copied over so they are not lost.
+    // Same as scala/scala/commit/79ca1408c7.
+    def initSuspendedMessages(oldRun: Run) = if oldRun != null then
+      mySuspendedMessages.clear()
+      mySuspendedMessages ++= oldRun.mySuspendedMessages
+
+    def suppressionsComplete(source: SourceFile) = source == NoSource || mySuppressionsComplete(source)
+
+    def addSuspendedMessage(warning: Warning) =
+      mySuspendedMessages.getOrElseUpdate(warning.pos.source, mutable.LinkedHashSet.empty) += warning
+
+    def nowarnAction(dia: Diagnostic): Action.Warning.type | Action.Verbose.type | Action.Silent.type =
+      mySuppressions.getOrElse(dia.pos.source, Nil).find(_.matches(dia)) match {
+        case Some(s) =>
+          s.markUsed()
+          if (s.verbose) Action.Verbose
+          else Action.Silent
+        case _ =>
+          Action.Warning
+      }
+
+    def addSuppression(sup: Suppression): Unit =
+      val source = sup.annotPos.source
+      mySuppressions.getOrElseUpdate(source, mutable.ListBuffer.empty) += sup
+
+    def reportSuspendedMessages(source: SourceFile)(using Context): Unit = {
+      // sort suppressions. they are not added in any particular order because of lazy type completion
+      for (sups <- mySuppressions.get(source))
+        mySuppressions(source) = sups.sortBy(sup => 0 - sup.start)
+      mySuppressionsComplete += source
+      mySuspendedMessages.remove(source).foreach(_.foreach(ctx.reporter.issueIfNotSuppressed))
+    }
+
+    def runFinished(hasErrors: Boolean): Unit =
+      // report suspended messages (in case the run finished before typer)
+      mySuspendedMessages.keysIterator.toList.foreach(reportSuspendedMessages)
+      // report unused nowarns only if all all phases are done
+      if !hasErrors && ctx.settings.WunusedHas.nowarn then
+        for {
+          source <- mySuppressions.keysIterator.toList
+          sups   <- mySuppressions.remove(source)
+          sup    <- sups.reverse
+        } if (!sup.used)
+          report.warning("@nowarn annotation does not suppress any warnings", sup.annotPos)
+
   /** The compilation units currently being compiled, this may return different
    *  results over time.
    */
@@ -222,7 +278,9 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
     runCtx.setProfiler(Profiler())
     unfusedPhases.foreach(_.initContext(runCtx))
     runPhases(using runCtx)
-    if (!ctx.reporter.hasErrors) Rewrites.writeBack()
+    if (!ctx.reporter.hasErrors)
+      Rewrites.writeBack()
+    suppressions.runFinished(hasErrors = ctx.reporter.hasErrors)
     while (finalizeActions.nonEmpty) {
       val action = finalizeActions.remove(0)
       action()

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

@@ -13,14 +13,17 @@ abstract class CompilerCommand extends CliCommand:
   type ConcreteSettings = ScalaSettings
 
   final def helpMsg(using settings: ScalaSettings)(using SettingsState, Context): String =
-    if (settings.help.value) usageMessage
-    else if (settings.Vhelp.value) vusageMessage
-    else if (settings.Whelp.value) wusageMessage
-    else if (settings.Xhelp.value) xusageMessage
-    else if (settings.Yhelp.value) yusageMessage
-    else if (settings.showPlugins.value) ctx.base.pluginDescriptions
-    else if (settings.XshowPhases.value) phasesMessage
-    else ""
+    settings.allSettings.find(isHelping) match
+      case Some(s) => s.description
+      case _ =>
+        if (settings.help.value) usageMessage
+        else if (settings.Vhelp.value) vusageMessage
+        else if (settings.Whelp.value) wusageMessage
+        else if (settings.Xhelp.value) xusageMessage
+        else if (settings.Yhelp.value) yusageMessage
+        else if (settings.showPlugins.value) ctx.base.pluginDescriptions
+        else if (settings.XshowPhases.value) phasesMessage
+        else ""
 
   final def isHelpFlag(using settings: ScalaSettings)(using SettingsState): Boolean =
     import settings._

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

@@ -1,11 +1,13 @@
 package dotty.tools.dotc
 package config
 
+import dotty.tools.dotc.config.PathResolver.Defaults
+import dotty.tools.dotc.config.Settings.{Setting, SettingGroup}
 import dotty.tools.dotc.core.Contexts._
-import dotty.tools.io.{ Directory, PlainDirectory, AbstractFile, JDK9Reflectors }
-import PathResolver.Defaults
-import rewrites.Rewrites
-import Settings.{ Setting, SettingGroup }
+import dotty.tools.dotc.rewrites.Rewrites
+import dotty.tools.io.{AbstractFile, Directory, JDK9Reflectors, PlainDirectory}
+
+import scala.util.chaining._
 
 class ScalaSettings extends SettingGroup with AllScalaSettings
 
@@ -51,7 +53,7 @@ trait AllScalaSettings extends CommonScalaSettings, VerboseSettings, WarningSett
   val explain: Setting[Boolean] = BooleanSetting("-explain", "Explain errors in more detail.", aliases = List("--explain"))
   val feature: Setting[Boolean] = BooleanSetting("-feature", "Emit warning and location for usages of features that should be imported explicitly.", aliases = List("--feature"))
   val source: Setting[String] = ChoiceSetting("-source", "source version", "source version", List("3.0", "future", "3.0-migration", "future-migration"), "3.0", aliases = List("--source"))
-  val unchecked: Setting[Boolean] = BooleanSetting("-unchecked", "Enable additional warnings where generated code depends on assumptions.", aliases = List("--unchecked"))
+  val unchecked: Setting[Boolean] = BooleanSetting("-unchecked", "Enable additional warnings where generated code depends on assumptions.", initialValue = true, aliases = List("--unchecked"))
   val uniqid: Setting[Boolean] = BooleanSetting("-uniqid", "Uniquely tag all identifiers in debugging output.", aliases = List("--unique-id"))
   val language: Setting[List[String]] = MultiStringSetting("-language", "feature", "Enable one or more language features.", aliases = List("--language"))
   val rewrite: Setting[Option[Rewrites]] = OptionSetting[Rewrites]("-rewrite", "When used in conjunction with a `...-migration` source version, rewrites sources to migrate to new version.", aliases = List("--rewrite"))
@@ -133,6 +135,64 @@ private sealed trait WarningSettings:
   val Whelp: Setting[Boolean] = BooleanSetting("-W", "Print a synopsis of warning options.")
   val XfatalWarnings: Setting[Boolean] = BooleanSetting("-Werror", "Fail the compilation if there are any warnings.", aliases = List("-Xfatal-warnings"))
 
+  val Wunused: Setting[List[String]] = MultiChoiceSetting(
+    name = "-Wunused",
+    helpArg = "warning",
+    descr = "Enable or disable specific `unused` warnings",
+    choices = List("nowarn", "all"),
+    default = Nil
+  )
+  object WunusedHas:
+    def allOr(s: String)(using Context) = Wunused.value.pipe(us => us.contains("all") || us.contains(s))
+    def nowarn(using Context) = allOr("nowarn")
+
+  val Wconf: Setting[List[String]] = MultiStringSetting(
+    "-Wconf",
+    "patterns",
+    default = List(),
+    descr =
+      s"""Configure compiler warnings.
+         |Syntax: -Wconf:<filters>:<action>,<filters>:<action>,...
+         |multiple <filters> are combined with &, i.e., <filter>&...&<filter>
+         |
+         |<filter>
+         |  - Any message: any
+         |
+         |  - Message categories: cat=deprecation, cat=feature, cat=unchecked
+         |
+         |  - Message content: msg=regex
+         |    The regex need only match some part of the message, not all of it.
+         |
+         |  - Message id: id=E129
+         |    The message id is printed with the warning.
+         |
+         |  - Message name: name=PureExpressionInStatementPosition
+         |    The message name is printed with the warning in verbose warning mode.
+         |
+         |In verbose warning mode the compiler prints matching filters for warnings.
+         |Verbose mode can be enabled globally using `-Wconf:any:verbose`, or locally
+         |using the @nowarn annotation (example: `@nowarn("v") def test = try 1`).
+         |
+         |<action>
+         |  - error / e
+         |  - warning / w
+         |  - verbose / v (emit warning, show additional help for writing `-Wconf` filters)
+         |  - info / i    (infos are not counted as warnings and not affected by `-Werror`)
+         |  - silent / s
+         |
+         |The default configuration is empty.
+         |
+         |User-defined configurations are added to the left. The leftmost rule matching
+         |a warning message defines the action.
+         |
+         |Examples:
+         |  - change every warning into an error: -Wconf:any:error
+         |  - silence deprecations: -Wconf:cat=deprecation:s
+         |
+         |Note: on the command-line you might need to quote configurations containing `*` or `&`
+         |to prevent the shell from expanding patterns.""".stripMargin,
+  )
+
 /** -X "Extended" or "Advanced" settings */
 private sealed trait XSettings:
   self: SettingGroup =>

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

@@ -56,7 +56,7 @@ object Settings:
     description: String,
     default: T,
     helpArg: String = "",
-    choices: Option[Seq[T]] = None,
+    choices: Option[Seq[?]] = None,
     prefix: String = "",
     aliases: List[String] = Nil,
     depends: List[(Setting[?], Any)] = Nil,
@@ -115,7 +115,13 @@ object Settings:
           update(Some(propertyClass.get.getConstructor().newInstance()), args)
         case (ListTag, _) =>
           if (argRest.isEmpty) missingArg
-          else update((argRest split ",").toList, args)
+          else
+            val strings = argRest.split(",").toList
+            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 _ => update(strings, args)
         case (StringTag, _) if argRest.nonEmpty || choices.exists(_.contains("")) =>
           setString(argRest, args)
         case (StringTag, arg2 :: args2) =>
@@ -251,14 +257,17 @@ object Settings:
     def ChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String], default: String, aliases: List[String] = Nil): Setting[String] =
       publish(Setting(name, descr, default, helpArg, Some(choices), aliases = aliases))
 
+    def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String], default: List[String], aliases: List[String] = Nil): Setting[List[String]] =
+      publish(Setting(name, descr, default, helpArg, Some(choices), aliases = aliases))
+
     def IntSetting(name: String, descr: String, default: Int, aliases: List[String] = Nil): Setting[Int] =
       publish(Setting(name, descr, default, aliases = aliases))
 
     def IntChoiceSetting(name: String, descr: String, choices: Seq[Int], default: Int): Setting[Int] =
       publish(Setting(name, descr, default, choices = Some(choices)))
 
-    def MultiStringSetting(name: String, helpArg: String, descr: String, aliases: List[String] = Nil): Setting[List[String]] =
-      publish(Setting(name, descr, Nil, helpArg, aliases = aliases))
+    def MultiStringSetting(name: String, helpArg: String, descr: String, default: List[String] = Nil, aliases: List[String] = Nil): Setting[List[String]] =
+      publish(Setting(name, descr, default, helpArg, aliases = aliases))
 
     def OutputSetting(name: String, helpArg: String, descr: String, default: AbstractFile): Setting[AbstractFile] =
       publish(Setting(name, descr, default, helpArg))

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -959,6 +959,8 @@ object Contexts {
 
     private[core] val reusableDataReader = ReusableInstance(new ReusableDataReader())
 
+    private[dotc] var wConfCache: (List[String], WConf) = _
+
     def sharedCharArray(len: Int): Array[Char] =
       while len > charArray.length do
         charArray = new Array[Char](charArray.length * 2)

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -903,6 +903,7 @@ class Definitions {
   @tu lazy val InvariantBetweenAnnot: ClassSymbol = requiredClass("scala.annotation.internal.InvariantBetween")
   @tu lazy val MainAnnot: ClassSymbol = requiredClass("scala.main")
   @tu lazy val MigrationAnnot: ClassSymbol = requiredClass("scala.annotation.migration")
+  @tu lazy val NowarnAnnot: ClassSymbol = requiredClass("scala.annotation.nowarn")
   @tu lazy val TransparentTraitAnnot: ClassSymbol = requiredClass("scala.annotation.transparentTrait")
   @tu lazy val NativeAnnot: ClassSymbol = requiredClass("scala.native")
   @tu lazy val RepeatedAnnot: ClassSymbol = requiredClass("scala.annotation.internal.Repeated")

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1158,10 +1158,11 @@ object Parsers {
           }
           else
             if !in.featureEnabled(Feature.symbolLiterals) then
+              val name = in.name // capture name (not `in`) in the warning message closure
               report.errorOrMigrationWarning(
-                em"""symbol literal '${in.name} is no longer supported,
-                    |use a string literal "${in.name}" or an application Symbol("${in.name}") instead,
-                    |or enclose in braces '{${in.name}} if you want a quoted expression.
+                em"""symbol literal '$name is no longer supported,
+                    |use a string literal "$name" or an application Symbol("$name") instead,
+                    |or enclose in braces '{$name} if you want a quoted expression.
                     |For now, you can also `import language.deprecated.symbolLiterals` to accept
                     |the idiom, but this possibility might no longer be available in the future.""",
                 in.sourcePos())

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

@@ -21,15 +21,7 @@ object report:
     ctx.reporter.report(new Info(msg, pos.sourcePos))
 
   private def issueWarning(warning: Warning)(using Context): Unit =
-    if (!ctx.settings.silentWarnings.value)
-      if (ctx.settings.XfatalWarnings.value)
-        warning match {
-          case warning: ConditionalWarning if !warning.enablingOption.value =>
-            ctx.reporter.report(warning) // conditional warnings that are not enabled are not fatal
-          case _ =>
-            ctx.reporter.report(warning.toError)
-        }
-      else ctx.reporter.report(warning)
+    ctx.reporter.report(warning)
 
   def deprecationWarning(msg: Message, pos: SrcPos = NoSourcePosition)(using Context): Unit =
     issueWarning(new DeprecationWarning(msg, pos.sourcePos))

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

@@ -21,21 +21,16 @@ class ConsoleReporter(
 
   /** Prints the message with the given position indication. */
   def doReport(dia: Diagnostic)(using Context): Unit = {
-    val didPrint = dia match {
+    dia match
       case dia: Error =>
-        printMessage(messageAndPos(dia.msg, dia.pos, diagnosticLevel(dia)))
+        printMessage(messageAndPos(dia))
         if (ctx.settings.Xprompt.value) Reporter.displayPrompt(reader, writer)
-        true
-      case dia: ConditionalWarning if !dia.enablingOption.value =>
-        false
       case dia =>
-        printMessage(messageAndPos(dia.msg, dia.pos, diagnosticLevel(dia)))
-        true
-    }
+        printMessage(messageAndPos(dia))
 
-    if (didPrint && shouldExplain(dia))
+    if shouldExplain(dia) then
       printMessage(explanation(dia.msg))
-    else if (didPrint && dia.msg.canExplain)
+    else if dia.msg.canExplain then
       printMessage("\nlonger explanation available when compiling with `-explain`")
   }
 

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

@@ -2,12 +2,13 @@ package dotty.tools
 package dotc
 package reporting
 
-import util.SourcePosition
-import core.Contexts._
-import config.Settings.Setting
-import interfaces.Diagnostic.{ERROR, INFO, WARNING}
+import dotty.tools.dotc.config.Settings.Setting
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.interfaces.Diagnostic.{ERROR, INFO, WARNING}
+import dotty.tools.dotc.util.SourcePosition
 
 import java.util.Optional
+import scala.util.chaining._
 
 object Diagnostic:
 
@@ -35,7 +36,9 @@ object Diagnostic:
     msg: Message,
     pos: SourcePosition
   ) extends Diagnostic(msg, pos, WARNING) {
-    def toError: Error = new Error(msg, pos)
+    def toError: Error = new Error(msg, pos).tap(e => if isVerbose then e.setVerbose())
+    def toInfo: Info = new Info(msg, pos).tap(e => if isVerbose then e.setVerbose())
+    def isSummarizedConditional(using Context): Boolean = false
   }
 
   class Info(
@@ -48,6 +51,7 @@ object Diagnostic:
     pos: SourcePosition
   ) extends Warning(msg, pos) {
     def enablingOption(using Context): Setting[Boolean]
+    override def isSummarizedConditional(using Context): Boolean = !enablingOption.value
   }
 
   class FeatureWarning(
@@ -81,6 +85,12 @@ class Diagnostic(
   val pos: SourcePosition,
   val level: Int
 ) extends Exception with interfaces.Diagnostic:
+  private var verbose: Boolean = false
+  def isVerbose: Boolean = verbose
+  def setVerbose(): this.type =
+    verbose = true
+    this
+
   override def position: Optional[interfaces.SourcePosition] =
     if (pos.exists && pos.source.exists) Optional.of(pos) else Optional.empty()
   override def message: String =

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

@@ -1,7 +1,7 @@
 package dotty.tools.dotc.reporting
 
 /** Unique IDs identifying the messages */
-enum ErrorMessageID extends java.lang.Enum[ErrorMessageID] {
+enum ErrorMessageID extends java.lang.Enum[ErrorMessageID]:
 
   // IMPORTANT: Add new IDs only at the end and never remove IDs
   case
@@ -177,4 +177,6 @@ enum ErrorMessageID extends java.lang.Enum[ErrorMessageID] {
     CannotExtendFunctionID
 
   def errorNumber = ordinal - 2
-}
+
+object ErrorMessageID:
+  def fromErrorNumber(n: Int) = fromOrdinal(n + 2)