SI-8610 -Xlint is multichoice option

Make -Xlint a "multichoice" option for purposes of option parsing.

This allows turning on "lint with these warnings" instead of only
"turn off these warnings but enable other lint warnings".

```
$ scalac -Xlint:warn-adapted-args linty.scala  # lint plus a warning
$ scalac -Xlint warn-adapted-args linty.scala  # same
$ scalac -Xlint linty.scala                    # same as now
$ scalac -Xlint -- linty.scala                 # ok, not necessary
$ scalac -Xlint _ -- linty.scala               # another funky underscore
```

This would also enable Xlint options that are not standalone options,
although that is not implemented in this commit.  For example,
`-Xlint:no-missing-interpolator` could be used to disable that
warning. (There is no `-Xoption:flavor=off` syntax.) (`no-` switches
would not be enabled by `_`.)

12 files changed, 116 insertions, 20 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
index 38a7525862..ef9695a594 100644
--- a/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
@@ -29,7 +29,7 @@ trait AbsScalaSettings {
   def ChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String], default: String): ChoiceSetting
   def IntSetting(name: String, descr: String, default: Int, range: Option[(Int, Int)], parser: String => Option[Int]): IntSetting
   def MultiStringSetting(name: String, helpArg: String, descr: String): MultiStringSetting
-  def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String]): MultiChoiceSetting
+  def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String], default: () => Unit): MultiChoiceSetting
   def OutputSetting(outputDirs: OutputDirs, default: String): OutputSetting
   def PathSetting(name: String, descr: String, default: String): PathSetting
   def PhasesSetting(name: String, descr: String, default: String): PhasesSetting
diff --git a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
index 54e444decf..5b5c80c514 100644
--- a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
@@ -211,10 +211,10 @@ class MutableSettings(val errorFn: String => Unit)
     add(new ChoiceSetting(name, helpArg, descr, choices, default))
   def IntSetting(name: String, descr: String, default: Int, range: Option[(Int, Int)], parser: String => Option[Int]) = add(new IntSetting(name, descr, default, range, parser))
   def MultiStringSetting(name: String, arg: String, descr: String) = add(new MultiStringSetting(name, arg, descr))
-  def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String]): MultiChoiceSetting = {
+  def MultiChoiceSetting(name: String, helpArg: String, descr: String, choices: List[String], default: () => Unit = () => ()): MultiChoiceSetting = {
     val fullChoix = choices.mkString(": ", ",", ".")
     val fullDescr = s"$descr$fullChoix"
-    add(new MultiChoiceSetting(name, helpArg, fullDescr, choices))
+    add(new MultiChoiceSetting(name, helpArg, fullDescr, choices, default))
   }
   def OutputSetting(outputDirs: OutputDirs, default: String) = add(new OutputSetting(outputDirs, default))
   def PhasesSetting(name: String, descr: String, default: String = "") = add(new PhasesSetting(name, descr, default))
@@ -553,12 +553,18 @@ class MutableSettings(val errorFn: String => Unit)
       }
   }
 
+  /** A setting that receives any combination of enumerated values,
+   *  including "_" to mean all values.
+   *  In non-colonated mode, stops consuming args at the first
+   *  non-value, instead of at the next option, as for a multi-string.
+   */
   class MultiChoiceSetting private[nsc](
     name: String,
     arg: String,
     descr: String,
-    override val choices: List[String])
-  extends MultiStringSetting(name, arg, descr)
+    override val choices: List[String],
+    override val default: () => Unit
+  ) extends MultiStringSetting(name, arg, descr)
 
   /** A setting that accumulates all strings supplied to it,
    *  until it encounters one starting with a '-'.
@@ -570,24 +576,34 @@ class MutableSettings(val errorFn: String => Unit)
   extends Setting(name, descr) with Clearable {
     type T = List[String]
     protected var v: T = Nil
+    val default: () => Unit = () => ()            // no natural default
     def appendToValue(str: String) { value ++= List(str) }
     def badChoice(s: String, n: String) = errorFn(s"'$s' is not a valid choice for '$name'")
 
-    def tryToSet(args: List[String]) = {
-      val (strings, rest) = args span (x => !x.startsWith("-"))
-      strings foreach {
-        case "_" if choices.nonEmpty => choices foreach appendToValue
+    private def tts(args: List[String], verify: Boolean) = {
+      def tryArg(arg: String) = arg match {
+        case "_" if choices.nonEmpty                      => choices foreach appendToValue
         case s if choices.isEmpty || (choices contains s) => appendToValue(s)
-        case s => badChoice(s, name)
+        case s                                            => badChoice(s, name)
       }
+      def loop(args: List[String]): List[String] = args match {
+        case Nil         => Nil
+        case arg :: _
+          if (arg startsWith "-") || (!verify && choices.nonEmpty && !(choices contains arg))
+                         => args
+        case arg :: rest => tryArg(arg) ; loop(rest)
+      }
+      val rest = loop(args)
+      if (rest.size == args.size) default()       // if no arg consumed, trigger default action
       Some(rest)
     }
-    override def tryToSetColon(args: List[String]) = tryToSet(args)
+    def tryToSet(args: List[String])                  = tts(args, verify = false)
+    override def tryToSetColon(args: List[String])    = tts(args, verify = true)
     override def tryToSetFromPropertyValue(s: String) = tryToSet(s.trim.split(',').toList) // used from ide
-    def clear(): Unit = (v = Nil)
-    def unparse: List[String] = value map (name + ":" + _)
 
-    def contains(s: String) = value contains s
+    def clear(): Unit         = (v = Nil)
+    def unparse: List[String] = value map (name + ":" + _)
+    def contains(s: String)   = value contains s
 
     withHelpSyntax(name + ":<" + arg + ">")
   }
@@ -606,10 +622,8 @@ class MutableSettings(val errorFn: String => Unit)
     protected var v: T = default
     def indexOfChoice: Int = choices indexOf value
 
-    private def usageErrorMessage = {
-      "Usage: %s:<%s>\n  where <%s> choices are %s (default: %s)\n".format(
-        name, helpArg, helpArg, choices mkString ", ", default)
-    }
+    private def usageErrorMessage = f"Usage: $name:<$helpArg>%n where <$helpArg> choices are ${choices mkString ", "} (default: $default)%n"
+
     def tryToSet(args: List[String]) = errorAndValue(usageErrorMessage, None)
 
     override def tryToSetColon(args: List[String]) = args match {
diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index 1509ad13b8..ae2696accf 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -50,8 +50,26 @@ trait Warnings {
   val warnUnused           = BooleanSetting   ("-Ywarn-unused", "Warn when local and private vals, vars, defs, and types are are unused")
   val warnUnusedImport     = BooleanSetting   ("-Ywarn-unused-import", "Warn when imports are unused")
 
-   // Warning groups.
-  val lint = BooleanSetting("-Xlint", "Enable recommended additional warnings.") enablingIfNotSetByUser lintWarnings
+  // Warning groups.
+  val lint                 = {
+    // Boolean setting for testing if lint is on; not "added" to option processing
+    val xlint = new BooleanSetting("-Xlint", "Enable recommended additional warnings.")
+    val lintables = (lintWarnings map (_.name drop 2)).sorted
+    def propagate(ss: List[String]): Unit = ss match {
+      case w :: rest => lintWarnings find (_.name == s"-Y$w") foreach (_.value = true) ; propagate(rest)
+      case Nil         => ()
+    }
+    def enableAll(): Unit = {   // enable lint and the group
+      xlint.value = true
+      for (s <- lintWarnings if !s.isSetByUser) s.value = true
+    }
+    // The command option
+    MultiChoiceSetting("-Xlint", "warning", "Enable recommended additional warnings", lintables, enableAll) withPostSetHook { x =>
+      propagate(x.value)      // enabling the selections (on each append to value)
+      xlint.value = true      // only enables lint, not the group
+    }
+    xlint
+  }
 
   // Backward compatibility.
   @deprecated("Use fatalWarnings", "2.11.0") def Xwarnfatal            = fatalWarnings      // used by sbt
diff --git a/test/files/neg/t8610-arg.check b/test/files/neg/t8610-arg.check
new file mode 100644
index 0000000000..f2879b0d45
--- /dev/null
+++ b/test/files/neg/t8610-arg.check
@@ -0,0 +1,9 @@
+t8610-arg.scala:3: warning: `$name` looks like an interpolated identifier! Did you forget the interpolator?
+  def x = "Hi, $name"   // missing interp
+          ^
+t8610-arg.scala:6: warning: side-effecting nullary methods are discouraged: suggest defining as `def u()` instead
+  def u: Unit = ()      // unitarian universalist
+      ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found
diff --git a/test/files/neg/t8610-arg.flags b/test/files/neg/t8610-arg.flags
new file mode 100644
index 0000000000..f8867a7b4e
--- /dev/null
+++ b/test/files/neg/t8610-arg.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Xlint warn-nullary-unit
diff --git a/test/files/neg/t8610-arg.scala b/test/files/neg/t8610-arg.scala
new file mode 100644
index 0000000000..494a3354da
--- /dev/null
+++ b/test/files/neg/t8610-arg.scala
@@ -0,0 +1,7 @@
+
+case class X(name: String) {
+  def x = "Hi, $name"   // missing interp
+  def f(p: (Int, Int)): Int = p._1 * p._2
+  def g = f(3, 4)       // adapted
+  def u: Unit = ()      // unitarian universalist
+}
diff --git a/test/files/neg/t8610.check b/test/files/neg/t8610.check
new file mode 100644
index 0000000000..7a18e55127
--- /dev/null
+++ b/test/files/neg/t8610.check
@@ -0,0 +1,15 @@
+t8610.scala:3: warning: `$name` looks like an interpolated identifier! Did you forget the interpolator?
+  def x = "Hi, $name"   // missing interp
+          ^
+t8610.scala:5: warning: Adapting argument list by creating a 2-tuple: this may not be what you want.
+        signature: X.f(p: (Int, Int)): Int
+  given arguments: 3, 4
+ after adaptation: X.f((3, 4): (Int, Int))
+  def g = f(3, 4)       // adapted
+           ^
+t8610.scala:6: warning: side-effecting nullary methods are discouraged: suggest defining as `def u()` instead
+  def u: Unit = ()      // unitarian universalist
+      ^
+error: No warnings can be incurred under -Xfatal-warnings.
+three warnings found
+one error found
diff --git a/test/files/neg/t8610.flags b/test/files/neg/t8610.flags
new file mode 100644
index 0000000000..954eaba352
--- /dev/null
+++ b/test/files/neg/t8610.flags
@@ -0,0 +1 @@
+-Xfatal-warnings -Xlint
diff --git a/test/files/neg/t8610.scala b/test/files/neg/t8610.scala
new file mode 100644
index 0000000000..494a3354da
--- /dev/null
+++ b/test/files/neg/t8610.scala
@@ -0,0 +1,7 @@
+
+case class X(name: String) {
+  def x = "Hi, $name"   // missing interp
+  def f(p: (Int, Int)): Int = p._1 * p._2
+  def g = f(3, 4)       // adapted
+  def u: Unit = ()      // unitarian universalist
+}
diff --git a/test/files/run/t8610.check b/test/files/run/t8610.check
new file mode 100644
index 0000000000..077382fb1c
--- /dev/null
+++ b/test/files/run/t8610.check
@@ -0,0 +1,10 @@
+t8610.scala:4: warning: `$name` looks like an interpolated identifier! Did you forget the interpolator?
+  def x = "Hi, $name"   // missing interp
+          ^
+t8610.scala:6: warning: Adapting argument list by creating a 2-tuple: this may not be what you want.
+        signature: X.f(p: (Int, Int)): Int
+  given arguments: 3, 4
+ after adaptation: X.f((3, 4): (Int, Int))
+  def g = f(3, 4)       // adapted
+           ^
+Hi, $name
diff --git a/test/files/run/t8610.flags b/test/files/run/t8610.flags
new file mode 100644
index 0000000000..edcb5f4d0c
--- /dev/null
+++ b/test/files/run/t8610.flags
@@ -0,0 +1 @@
+-Xlint:warn-adapted-args
diff --git a/test/files/run/t8610.scala b/test/files/run/t8610.scala
new file mode 100644
index 0000000000..dd9e8e861e
--- /dev/null
+++ b/test/files/run/t8610.scala
@@ -0,0 +1,13 @@
+
+// flags don't warn on u
+case class X(name: String) {
+  def x = "Hi, $name"   // missing interp
+  def f(p: (Int, Int)): Int = p._1 * p._2
+  def g = f(3, 4)       // adapted
+  def u: Unit = ()      // unitarian universalist
+}
+
+object Test extends App {
+  // poignant demonstration
+  Console println X("Bob").x
+}