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.

4 files changed, 45 insertions, 0 deletions

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")
+  }
+}
+