Fix default value for ScalaVersionSetting

The default value was NoScalaVersion before, because tryToSet (where
the default was supposed to be set) is not called at all if the option
is not specified.

The initial value of Xmigration is set to NoScalaVersion (which it was
before, the AnyScalaVersion argument was ignored). AnyScalaVersion
would be wrong, it would give a warning in `Map(1 -> "eis").values`
if the option was not specified. See tests.

2 files changed, 21 insertions, 12 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
index 23611bb629..b4987e1240 100644
--- a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
@@ -229,7 +229,8 @@ class MutableSettings(val errorFn: String => Unit)
   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))
   def StringSetting(name: String, arg: String, descr: String, default: String) = add(new StringSetting(name, arg, descr, default))
-  def ScalaVersionSetting(name: String, arg: String, descr: String, default: ScalaVersion) = add(new ScalaVersionSetting(name, arg, descr, default))
+  def ScalaVersionSetting(name: String, arg: String, descr: String, initial: ScalaVersion, default: Option[ScalaVersion] = None) =
+    add(new ScalaVersionSetting(name, arg, descr, initial, default))
   def PathSetting(name: String, descr: String, default: String): PathSetting = {
     val prepend = StringSetting(name + "/p", "", "", "").internalOnly()
     val append = StringSetting(name + "/a", "", "", "").internalOnly()
@@ -506,28 +507,35 @@ class MutableSettings(val errorFn: String => Unit)
     withHelpSyntax(name + " <" + arg + ">")
   }
 
-  /** A setting represented by a Scala version, (`default` unless set) */
+  /** A setting represented by a Scala version.
+    * The `initial` value is used if the setting is not specified.
+    * The `default` value is used if the option is specified without argument (e.g., `-Xmigration`).
+    */
   class ScalaVersionSetting private[nsc](
     name: String,
     val arg: String,
     descr: String,
-    default: ScalaVersion)
+    initial: ScalaVersion,
+    default: Option[ScalaVersion])
   extends Setting(name, descr) {
     type T = ScalaVersion
-    protected var v: T = NoScalaVersion
+    protected var v: T = initial
 
+    // This method is invoked if there are no colonated args. In this case the default value is
+    // used. No arguments are consumed.
     override def tryToSet(args: List[String]) = {
-      value = default
+      default match {
+        case Some(d) => value = d
+        case None => errorFn(s"$name requires an argument, the syntax is $helpSyntax")
+      }
       Some(args)
     }
 
     override def tryToSetColon(args: List[String]) = args match {
-      case Nil      => value = default; Some(Nil)
-      case x :: xs  => value = ScalaVersion(x, errorFn) ; Some(xs)
+      case x :: xs  => value = ScalaVersion(x, errorFn); Some(xs)
+      case nil      => Some(nil)
     }
 
-    override def tryToSetFromPropertyValue(s: String) = tryToSet(List(s))
-
     def unparse: List[String] = if (value == NoScalaVersion) Nil else List(s"${name}:${value.unparse}")
 
     withHelpSyntax(s"${name}:<${arg}>")
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 850534f2cc..c59d56d8f8 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -92,7 +92,8 @@ trait ScalaSettings extends AbsScalaSettings
    * The previous "-source" option is intended to be used mainly
    * though this helper.
    */
-  lazy val isScala211: Boolean = (source.value >= ScalaVersion("2.11.0"))
+  def isScala211: Boolean = source.value >= ScalaVersion("2.11.0")
+  def isScala212: Boolean = source.value >= ScalaVersion("2.12.0")
 
   /**
    * -X "Advanced" settings
@@ -111,7 +112,7 @@ trait ScalaSettings extends AbsScalaSettings
   val logFreeTerms       = BooleanSetting      ("-Xlog-free-terms", "Print a message when reification creates a free term.")
   val logFreeTypes       = BooleanSetting      ("-Xlog-free-types", "Print a message when reification resorts to generating a free type.")
   val maxClassfileName   = IntSetting          ("-Xmax-classfile-name", "Maximum filename length for generated classes", 255, Some((72, 255)), _ => None)
-  val Xmigration         = ScalaVersionSetting ("-Xmigration", "version", "Warn about constructs whose behavior may have changed since version.", AnyScalaVersion)
+  val Xmigration         = ScalaVersionSetting ("-Xmigration", "version", "Warn about constructs whose behavior may have changed since version.", initial = NoScalaVersion, default = Some(AnyScalaVersion))
   val nouescape          = BooleanSetting      ("-Xno-uescape", "Disable handling of \\u unicode escapes.")
   val Xnojline           = BooleanSetting      ("-Xnojline", "Do not use JLine for editing.")
   val Xverify            = BooleanSetting      ("-Xverify", "Verify generic signatures in generated bytecode (asm backend only.)")
@@ -133,7 +134,7 @@ trait ScalaSettings extends AbsScalaSettings
   val showPhases         = BooleanSetting      ("-Xshow-phases", "Print a synopsis of compiler phases.")
   val sourceReader       = StringSetting       ("-Xsource-reader", "classname", "Specify a custom method for reading source files.", "")
   val strictInference    = BooleanSetting      ("-Xstrict-inference", "Don't infer known-unsound types")
-  val source             = ScalaVersionSetting ("-Xsource", "version", "Treat compiler input as Scala source for the specified version, see SI-8126.", ScalaVersion("2.11")) withPostSetHook ( _ => isScala211)
+  val source             = ScalaVersionSetting ("-Xsource", "version", "Treat compiler input as Scala source for the specified version, see SI-8126.", initial = ScalaVersion("2.11"))
 
   val XnoPatmatAnalysis = BooleanSetting ("-Xno-patmat-analysis", "Don't perform exhaustivity/unreachability analysis. Also, ignore @switch annotation.")
   val XfullLubs         = BooleanSetting ("-Xfull-lubs", "Retains pre 2.10 behavior of less aggressive truncation of least upper bounds.")