Put longlit deprecation behind -Xlint

Also add deprecation to -Xlint, where it just
enables the deprecation setting.

Author: som-snytt

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

@@ -9,7 +9,7 @@ import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.rewrites.Rewrites
 import dotty.tools.io.{AbstractFile, Directory, JDK9Reflectors, PlainDirectory}
 
-import scala.util.chaining._
+import scala.util.chaining.given
 
 class ScalaSettings extends SettingGroup with AllScalaSettings
 
@@ -143,9 +143,13 @@ private sealed trait VerboseSettings:
 /** -W "Warnings" settings
  */
 private sealed trait WarningSettings:
-  self: SettingGroup =>
+  self: SettingGroup & CommonScalaSettings =>
   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"))
+  private def syncDeprecation(ss: Settings.SettingsState) =
+    if Xlint.valueIn(ss).contains("deprecation") then self.deprecation.updateIn(ss, true) else ss
+  val Xlint: Setting[List[String]] = EnumSetting("-Wlint", "warning", "Enable recommended warnings.", LintWarning.values, default = Nil, aliases = List("-Xlint"), onUpdate = syncDeprecation)
+  def isLintEnabled(w: LintWarning)(using Context): Boolean = Xlint.value.contains(w.toString)
 
   val Wunused: Setting[List[String]] = MultiChoiceSetting(
     name = "-Wunused",
@@ -327,3 +331,8 @@ private sealed trait YSettings:
 
   val YforceInlineWhileTyping: Setting[Boolean] = BooleanSetting("-Yforce-inline-while-typing", "Make non-transparent inline methods inline when typing. Emulates the old inlining behavior of 3.0.0-M3.")
 end YSettings
+
+/** Warnings that may be queried with `ctx.settings.isLintEnabled`. */
+enum LintWarning:
+  case deprecation, longLit
+end LintWarning

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

@@ -9,7 +9,7 @@ import dotty.tools.io.{AbstractFile, Directory, JarArchive, PlainDirectory}
 
 import annotation.tailrec
 import collection.mutable.ArrayBuffer
-import reflect.ClassTag
+import reflect.{ClassTag, Enum}
 import scala.util.{Success, Failure}
 
 object Settings:
@@ -61,14 +61,16 @@ object Settings:
     prefix: String = "",
     aliases: List[String] = Nil,
     depends: List[(Setting[?], Any)] = Nil,
-    propertyClass: Option[Class[?]] = None)(private[Settings] val idx: Int) {
+    propertyClass: Option[Class[?]] = None,
+    onUpdate: SettingsState => SettingsState = s => s,
+  )(private[Settings] val idx: Int) {
 
     private var changed: Boolean = false
 
     def valueIn(state: SettingsState): T = state.value(idx).asInstanceOf[T]
 
     def updateIn(state: SettingsState, x: Any): SettingsState = x match
-      case _: T => state.update(idx, x)
+      case _: T => onUpdate(state.update(idx, x))
       case _ => throw IllegalArgumentException(s"found: $x of type ${x.getClass.getName}, required: ${implicitly[ClassTag[T]]}")
 
     def isDefaultIn(state: SettingsState): Boolean = valueIn(state) == default
@@ -265,6 +267,9 @@ object Settings:
     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 EnumSetting[E <: Enum](name: String, helpArg: String, descr: String, choices: Array[E], default: List[String], aliases: List[String] = Nil, onUpdate: SettingsState => SettingsState): Setting[List[String]] =
+      publish(Setting(name, descr, default, helpArg, Some(choices.toList.map(_.toString)), aliases = aliases, onUpdate = onUpdate))
+
     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/parsing/Scanners.scala

@@ -11,6 +11,7 @@ import util.Chars._
 import util.{SourcePosition, CharBuffer}
 import util.Spans.Span
 import config.Config
+import config.LintWarning
 import Tokens._
 import scala.annotation.{switch, tailrec}
 import scala.collection.mutable
@@ -1450,7 +1451,7 @@ object Scanners {
         getFraction()
       // 1l is an acknowledged bad practice
       def lintel(): Unit =
-        if ch == 'l' then
+        if ch == 'l' && ctx.settings.isLintEnabled(LintWarning.longLit) then
           val msg = "Lowercase el for long is not recommended because it is easy to confuse with numeral 1; use uppercase L instead"
           report.deprecationWarning(msg, sourcePos(offset + litBuf.length))
       // after int: 5e7f, 42L, 42.toDouble but not 42b.

tests/neg-with-compiler/longlit.scala

@@ -0,0 +1,11 @@
+// scalac: -Werror -Xlint:longLit,deprecation
+
+trait DejectedLiterals:
+
+  def bad = 1l        // error
+
+  def worse = 123l    // error
+
+  def worstest = 32l  // error
+
+// Lowercase el for long is not recommended because it is easy to confuse with numeral 1; use uppercase L instead