SI-5905 Sanity check -language options

The option names are hardcoded, but checked by a test.

There are no hooks to verify options after the compiler
is constructed.

Introduced a `MultiChoiceSetting` required for the
setting creation framework.

7 files changed, 74 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
index 8b897b83b2..38a7525862 100644
--- a/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/AbsScalaSettings.scala
@@ -16,6 +16,7 @@ trait AbsScalaSettings {
   type ChoiceSetting      <: Setting { type T = String }
   type IntSetting         <: Setting { type T = Int }
   type MultiStringSetting <: Setting { type T = List[String] }
+  type MultiChoiceSetting <: Setting { type T = List[String] }
   type PathSetting        <: Setting { type T = String }
   type PhasesSetting      <: Setting { type T = List[String] }
   type StringSetting      <: Setting { type T = String }
@@ -28,6 +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 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 3590254128..c22dc564b2 100644
--- a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
@@ -211,6 +211,11 @@ 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 = {
+    val fullChoix = choices.mkString(": ", ",", ".")
+    val fullDescr = s"$descr$fullChoix"
+    add(new MultiChoiceSetting(name, helpArg, fullDescr, choices))
+  }
   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))
@@ -548,8 +553,16 @@ class MutableSettings(val errorFn: String => Unit)
       }
   }
 
+  class MultiChoiceSetting private[nsc](
+    name: String,
+    arg: String,
+    descr: String,
+    override val choices: List[String])
+  extends MultiStringSetting(name, arg, descr)
+
   /** A setting that accumulates all strings supplied to it,
-   *  until it encounters one starting with a '-'. */
+   *  until it encounters one starting with a '-'.
+   */
   class MultiStringSetting private[nsc](
     name: String,
     val arg: String,
@@ -558,11 +571,14 @@ class MutableSettings(val errorFn: String => Unit)
     type T = List[String]
     protected var v: T = Nil
     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 appendToValue
-
+      strings foreach {
+        case s if choices.isEmpty || (choices contains s) => appendToValue(s)
+        case s => badChoice(s, name)
+      }
       Some(rest)
     }
     override def tryToSetColon(args: List[String]) = tryToSet(args)
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index a643a08614..20ccc30ff6 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -62,8 +62,14 @@ trait ScalaSettings extends AbsScalaSettings
   /*val argfiles = */ BooleanSetting    ("@<file>", "A text file containing compiler arguments (options and source files)")
   val classpath     = PathSetting       ("-classpath", "Specify where to find user class files.", defaultClasspath) withAbbreviation "-cp"
   val d             = OutputSetting     (outputDirs, ".")
-  val nospecialization = BooleanSetting    ("-no-specialization", "Ignore @specialize annotations.")
-  val language      = MultiStringSetting("-language", "feature", "Enable one or more language features.")
+  val nospecialization = BooleanSetting ("-no-specialization", "Ignore @specialize annotations.")
+
+  // Would be nice to build this dynamically from scala.languageFeature.
+  // The two requirements: delay error checking until you have symbols, and let compiler command build option-specific help.
+  val language      = {
+    val features = List("dynamics", "postfixOps", "reflectiveCalls", "implicitConversions", "higherKinds", "existentials", "experimental.macros")
+    MultiChoiceSetting("-language", "feature", "Enable one or more language features", features)
+  }
 
   /*
    * The previous "-source" option is intended to be used mainly
diff --git a/test/files/run/t5905-features.flags b/test/files/run/t5905-features.flags
new file mode 100644
index 0000000000..ad51758c39
--- /dev/null
+++ b/test/files/run/t5905-features.flags
@@ -0,0 +1 @@
+-nowarn
diff --git a/test/files/run/t5905-features.scala b/test/files/run/t5905-features.scala
new file mode 100644
index 0000000000..fbffddf114
--- /dev/null
+++ b/test/files/run/t5905-features.scala
@@ -0,0 +1,28 @@
+
+import tools.partest.DirectTest
+
+// verify that all languageFeature names are accepted by -language
+object Test extends DirectTest {
+  override def code = "class Code { def f = (1 to 10) size }" // exercise a feature
+
+  override def extraSettings = s"-usejavacp -d ${testOutput.path}"
+
+  override def show() = {
+    val global = newCompiler("-language:postfixOps", "-Ystop-after:typer")
+    compileString(global)(code)
+    import global._
+    exitingTyper {
+      def isFeature(s: Symbol) = s.annotations.exists((a: AnnotationInfo) => a.tpe <:< typeOf[scala.annotation.meta.languageFeature])
+      val langf  = definitions.languageFeatureModule.typeSignature
+      val feats  = langf.declarations filter (s => isFeature(s)) map (_.name.decoded)
+      val xmen   = langf.member(TermName("experimental")).typeSignature.declarations filter (s => isFeature(s)) map (s => s"experimental.${s.name.decoded}")
+      val all    = (feats ++ xmen) mkString ","
+
+      assert(feats.nonEmpty, "Test must find feature flags.")
+
+      //dynamics,postfixOps,reflectiveCalls,implicitConversions,higherKinds,existentials,experimental.macros
+      compile(s"-language:$all")
+    }
+  }
+}
+
diff --git a/test/files/run/t5905b-features.check b/test/files/run/t5905b-features.check
new file mode 100644
index 0000000000..08c76d74aa
--- /dev/null
+++ b/test/files/run/t5905b-features.check
@@ -0,0 +1 @@
+'noob' is not a valid choice for '-language'
diff --git a/test/files/run/t5905b-features.scala b/test/files/run/t5905b-features.scala
new file mode 100644
index 0000000000..627df8334b
--- /dev/null
+++ b/test/files/run/t5905b-features.scala
@@ -0,0 +1,15 @@
+
+import tools.partest.DirectTest
+
+// verify that only languageFeature names are accepted by -language
+object Test extends DirectTest {
+  override def code = "class Code"
+
+  override def extraSettings = s"-usejavacp -d ${testOutput.path}"
+
+  override def show() = {
+    //compile("-language", "--")  // no error
+    compile(s"-language:noob")
+  }
+}
+