Add the -Wall option that enables all warnings

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

@@ -158,43 +158,54 @@ private sealed trait WarningSettings:
 
   val Whelp: Setting[Boolean] = BooleanSetting(WarningSetting, "W", "Print a synopsis of warning options.")
   val XfatalWarnings: Setting[Boolean] = BooleanSetting(WarningSetting, "Werror", "Fail the compilation if there are any warnings.", aliases = List("-Xfatal-warnings"))
-  val WvalueDiscard: Setting[Boolean] = BooleanSetting(WarningSetting, "Wvalue-discard", "Warn when non-Unit expression results are unused.")
-  val WNonUnitStatement = BooleanSetting(WarningSetting, "Wnonunit-statement", "Warn when block statements are non-Unit expressions.")
-  val WenumCommentDiscard = BooleanSetting(WarningSetting, "Wenum-comment-discard", "Warn when a comment ambiguously assigned to multiple enum cases is discarded.")
-  val WimplausiblePatterns = BooleanSetting(WarningSetting, "Wimplausible-patterns", "Warn if comparison with a pattern value looks like it might always fail.")
-  val WunstableInlineAccessors = BooleanSetting(WarningSetting, "WunstableInlineAccessors", "Warn an inline methods has references to non-stable binary APIs.")
+  val Wall: Setting[Boolean] = BooleanSetting(WarningSetting, "Wall", "Enable all warnings.")
+  private val overrideWithWall: (Setting[Boolean], (Boolean, Any) => Boolean) =
+    (Wall, (a, b) => a || b.asInstanceOf[Boolean])
+  val WvalueDiscard: Setting[Boolean] = BooleanSetting(WarningSetting, "Wvalue-discard", "Warn when non-Unit expression results are unused.", overriddenBy = overrideWithWall)
+  val WNonUnitStatement = BooleanSetting(WarningSetting, "Wnonunit-statement", "Warn when block statements are non-Unit expressions.", overriddenBy = overrideWithWall)
+  val WenumCommentDiscard = BooleanSetting(WarningSetting, "Wenum-comment-discard", "Warn when a comment ambiguously assigned to multiple enum cases is discarded.", overriddenBy = overrideWithWall)
+  val WimplausiblePatterns = BooleanSetting(WarningSetting, "Wimplausible-patterns", "Warn if comparison with a pattern value looks like it might always fail.", overriddenBy = overrideWithWall)
+  val WunstableInlineAccessors = BooleanSetting(WarningSetting, "WunstableInlineAccessors", "Warn an inline methods has references to non-stable binary APIs.", overriddenBy = overrideWithWall)
+  val WunusedAll = ChoiceWithHelp("all", "")
+  private val overrideWunusedWithWall: (Setting[Boolean], (List[ChoiceWithHelp[String]], Any) => List[ChoiceWithHelp[String]]) =
+    def updateValue(fromUser: List[ChoiceWithHelp[String]], fromWall: Any): List[ChoiceWithHelp[String]] =
+      if fromUser.isEmpty && fromWall.asInstanceOf[Boolean] then
+        List(WunusedAll)
+      else fromUser
+    (Wall, updateValue)
   val Wunused: Setting[List[ChoiceWithHelp[String]]] = MultiChoiceHelpSetting(
     WarningSetting,
     name = "Wunused",
     helpArg = "warning",
     descr = "Enable or disable specific `unused` warnings",
     choices = List(
       ChoiceWithHelp("nowarn", ""),
-      ChoiceWithHelp("all",""),
+      WunusedAll,
       ChoiceWithHelp(
         name = "imports",
         description = "Warn if an import selector is not referenced.\n" +
         "NOTE : overrided by -Wunused:strict-no-implicit-warn"),
-        ChoiceWithHelp("privates","Warn if a private member is unused"),
-        ChoiceWithHelp("locals","Warn if a local definition is unused"),
-        ChoiceWithHelp("explicits","Warn if an explicit parameter is unused"),
-        ChoiceWithHelp("implicits","Warn if an implicit parameter is unused"),
-        ChoiceWithHelp("params","Enable -Wunused:explicits,implicits"),
-        ChoiceWithHelp("linted","Enable -Wunused:imports,privates,locals,implicits"),
-        ChoiceWithHelp(
-          name = "strict-no-implicit-warn",
-          description = "Same as -Wunused:import, only for imports of explicit named members.\n" +
-          "NOTE : This overrides -Wunused:imports and NOT set by -Wunused:all"
-        ),
-        // ChoiceWithHelp("patvars","Warn if a variable bound in a pattern is unused"),
-        ChoiceWithHelp(
-          name = "unsafe-warn-patvars",
-          description = "(UNSAFE) Warn if a variable bound in a pattern is unused.\n" +
-          "This warning can generate false positive, as warning cannot be\n" +
-          "suppressed yet."
-        )
+      ChoiceWithHelp("privates","Warn if a private member is unused"),
+      ChoiceWithHelp("locals","Warn if a local definition is unused"),
+      ChoiceWithHelp("explicits","Warn if an explicit parameter is unused"),
+      ChoiceWithHelp("implicits","Warn if an implicit parameter is unused"),
+      ChoiceWithHelp("params","Enable -Wunused:explicits,implicits"),
+      ChoiceWithHelp("linted","Enable -Wunused:imports,privates,locals,implicits"),
+      ChoiceWithHelp(
+        name = "strict-no-implicit-warn",
+        description = "Same as -Wunused:import, only for imports of explicit named members.\n" +
+        "NOTE : This overrides -Wunused:imports and NOT set by -Wunused:all"
+      ),
+      // ChoiceWithHelp("patvars","Warn if a variable bound in a pattern is unused"),
+      ChoiceWithHelp(
+        name = "unsafe-warn-patvars",
+        description = "(UNSAFE) Warn if a variable bound in a pattern is unused.\n" +
+        "This warning can generate false positive, as warning cannot be\n" +
+        "suppressed yet."
+      )
     ),
-    default = Nil
+    default = Nil,
+    overriddenBy = overrideWunusedWithWall,
   )
   object WunusedHas:
     def isChoiceSet(s: String)(using Context) = Wunused.value.pipe(us => us.contains(s))
@@ -296,7 +307,7 @@ private sealed trait WarningSettings:
     def typeParameterShadow(using Context) =
       allOr("type-parameter-shadow")
 
-  val WcheckInit: Setting[Boolean] = BooleanSetting(WarningSetting, "Wsafe-init", "Ensure safe initialization of objects.")
+  val WcheckInit: Setting[Boolean] = BooleanSetting(WarningSetting, "Wsafe-init", "Ensure safe initialization of objects.", overriddenBy = overrideWithWall)
 
 /** -X "Extended" or "Advanced" settings */
 private sealed trait XSettings:

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

@@ -87,7 +87,9 @@ object Settings:
     // kept only for -Xkind-projector option compatibility
     legacyArgs: Boolean = false,
     // accept legacy choices (for example, valid in Scala 2 but no longer supported)
-    legacyChoices: Option[Seq[?]] = None)(private[Settings] val idx: Int):
+    legacyChoices: Option[Seq[?]] = None,
+    // override the value of this setting based on the value of another one
+    overriddenBy: (Setting[?], (T, Any) => T) | Null = null)(private[Settings] val idx: Int):
 
     validateSettingString(prefix.getOrElse(name))
     aliases.foreach(validateSettingString)
@@ -99,7 +101,14 @@ object Settings:
 
     val allFullNames: List[String] = s"$name" :: s"-$name" :: aliases
 
-    def valueIn(state: SettingsState): T = state.value(idx).asInstanceOf[T]
+    def valueIn(state: SettingsState): T =
+      val thisVal = state.value(idx).asInstanceOf[T]
+      if overriddenBy == null then
+        thisVal
+      else
+        val (that, f) = overriddenBy.nn
+        val thatVal = that.valueIn(state)
+        f(thisVal, thatVal)
 
     def updateIn(state: SettingsState, x: Any): SettingsState = x match
       case _: T => state.update(idx, x)
@@ -378,8 +387,8 @@ object Settings:
       assert(!name.startsWith("-"), s"Setting $name cannot start with -")
       "-" + name
 
-    def BooleanSetting(category: SettingCategory, name: String, descr: String, initialValue: Boolean = false, aliases: List[String] = Nil, preferPrevious: Boolean = false, deprecation: Option[Deprecation] = None, ignoreInvalidArgs: Boolean = false): Setting[Boolean] =
-      publish(Setting(category, prependName(name), descr, initialValue, aliases = aliases, preferPrevious = preferPrevious, deprecation = deprecation, ignoreInvalidArgs = ignoreInvalidArgs))
+    def BooleanSetting(category: SettingCategory, name: String, descr: String, initialValue: Boolean = false, aliases: List[String] = Nil, preferPrevious: Boolean = false, deprecation: Option[Deprecation] = None, ignoreInvalidArgs: Boolean = false, overriddenBy: (Setting[?], (Boolean, Any) => Boolean) | Null = null): Setting[Boolean] =
+      publish(Setting(category, prependName(name), descr, initialValue, aliases = aliases, preferPrevious = preferPrevious, deprecation = deprecation, ignoreInvalidArgs = ignoreInvalidArgs, overriddenBy = overriddenBy))
 
     def StringSetting(category: SettingCategory, name: String, helpArg: String, descr: String, default: String, aliases: List[String] = Nil, deprecation: Option[Deprecation] = None): Setting[String] =
       publish(Setting(category, prependName(name), descr, default, helpArg, aliases = aliases, deprecation = deprecation))
@@ -390,8 +399,8 @@ object Settings:
     def MultiChoiceSetting(category: SettingCategory, name: String, helpArg: String, descr: String, choices: List[String], default: List[String] = Nil, legacyChoices: List[String] = Nil, aliases: List[String] = Nil, deprecation: Option[Deprecation] = None): Setting[List[String]] =
       publish(Setting(category, prependName(name), descr, default, helpArg, Some(choices), legacyChoices = Some(legacyChoices), aliases = aliases, deprecation = deprecation))
 
-    def MultiChoiceHelpSetting(category: SettingCategory, name: String, helpArg: String, descr: String, choices: List[ChoiceWithHelp[String]], default: List[ChoiceWithHelp[String]], legacyChoices: List[String] = Nil, aliases: List[String] = Nil, deprecation: Option[Deprecation] = None): Setting[List[ChoiceWithHelp[String]]] =
-      publish(Setting(category, prependName(name), descr, default, helpArg, Some(choices), legacyChoices = Some(legacyChoices), aliases = aliases, deprecation = deprecation))
+    def MultiChoiceHelpSetting(category: SettingCategory, name: String, helpArg: String, descr: String, choices: List[ChoiceWithHelp[String]], default: List[ChoiceWithHelp[String]], legacyChoices: List[String] = Nil, aliases: List[String] = Nil, deprecation: Option[Deprecation] = None, overriddenBy: (Setting[?], (List[ChoiceWithHelp[String]], Any) => List[ChoiceWithHelp[String]]) | Null = null): Setting[List[ChoiceWithHelp[String]]] =
+      publish(Setting(category, prependName(name), descr, default, helpArg, Some(choices), legacyChoices = Some(legacyChoices), aliases = aliases, deprecation = deprecation, overriddenBy = overriddenBy))
 
     def IntSetting(category: SettingCategory, name: String, descr: String, default: Int, aliases: List[String] = Nil, deprecation: Option[Deprecation] = None): Setting[Int] =
       publish(Setting(category, prependName(name), descr, default, aliases = aliases, deprecation = deprecation))

tests/warn/i18559a.check

@@ -0,0 +1,12 @@
+-- [E198] Unused Symbol Warning: tests/warn/i18559a.scala:4:28 ---------------------------------------------------------
+4 |  import collection.mutable.Set // warn
+  |                            ^^^
+  |                            unused import
+-- [E198] Unused Symbol Warning: tests/warn/i18559a.scala:8:8 ----------------------------------------------------------
+8 |    val x = 1  // warn
+  |        ^
+  |        unused local definition
+-- [E198] Unused Symbol Warning: tests/warn/i18559a.scala:11:26 --------------------------------------------------------
+11 |  import SomeGivenImports.given // warn
+   |                          ^^^^^
+   |                          unused import

tests/warn/i18559a.scala

@@ -0,0 +1,15 @@
+//> using options -Wall
+// This test checks that -Wall turns on -Wunused:all if -Wunused is not set
+object FooImportUnused:
+  import collection.mutable.Set // warn
+
+object FooUnusedLocal:
+  def test(): Unit =
+    val x = 1  // warn
+
+object FooGivenUnused:
+  import SomeGivenImports.given // warn
+
+object SomeGivenImports:
+  given Int = 0
+  given String = "foo"

tests/warn/i18559b.check

@@ -0,0 +1,12 @@
+-- Warning: tests/warn/i18559b.scala:8:6 -------------------------------------------------------------------------------
+8 |  val localFile: String = s"${url.##}.tmp"  // warn
+  |      ^
+  |      Access non-initialized value localFile. Calling trace:
+  |      ├── class RemoteFile(url: String) extends AbstractFile:	[ i18559b.scala:7 ]
+  |      │   ^
+  |      ├── abstract class AbstractFile:	[ i18559b.scala:3 ]
+  |      │   ^
+  |      ├── val extension: String = name.substring(4)	[ i18559b.scala:5 ]
+  |      │                           ^^^^
+  |      └── def name: String = localFile	[ i18559b.scala:9 ]
+  |                             ^^^^^^^^^

tests/warn/i18559b.scala

@@ -0,0 +1,9 @@
+//> using options -Wall
+// This test checks that -Wall turns on -Wsafe-init
+abstract class AbstractFile:
+  def name: String
+  val extension: String = name.substring(4)
+
+class RemoteFile(url: String) extends AbstractFile:
+  val localFile: String = s"${url.##}.tmp"  // warn
+  def name: String = localFile

tests/warn/i18559c.check

@@ -0,0 +1,4 @@
+-- [E198] Unused Symbol Warning: tests/warn/i18559c.scala:8:8 ----------------------------------------------------------
+8 |    val x = 1  // warn
+  |        ^
+  |        unused local definition

tests/warn/i18559c.scala

@@ -0,0 +1,15 @@
+//> using options -Wall -Wunused:locals
+// This test checks that -Wall leaves -Wunused:... untouched if it is already set
+object FooImportUnused:
+  import collection.mutable.Set // not warn
+
+object FooUnusedLocal:
+  def test(): Unit =
+    val x = 1  // warn
+
+object FooGivenUnused:
+  import SomeGivenImports.given // not warn
+
+object SomeGivenImports:
+  given Int = 0
+  given String = "foo"