Merge pull request scala#3777 from som-snytt/issue/5905-test

SI-5905 Clarify test case

Author: retronym

test/files/run/t5905-features.scala

@@ -3,13 +3,13 @@ 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 code = "class Code { def f = (1 to 10) size }" // exercise a feature to sanity-check coverage of -language options
 
   override def extraSettings = s"-usejavacp -d ${testOutput.path}"
 
   override def show() = {
-    val global = newCompiler("-language:postfixOps", "-Ystop-after:typer")
-    compileString(global)(code)
+    val global = newCompiler("-Ystop-after:typer")
+    compileString(global)("")   // warm me up, scotty
     import global._
     exitingTyper {
       //def isFeature(s: Symbol) = s.annotations.exists((a: AnnotationInfo) => a.tpe <:< typeOf[scala.annotation.meta.languageFeature])
@@ -21,6 +21,8 @@ object Test extends DirectTest {
 
       assert(feats.nonEmpty, "Test must find feature flags.")
 
+      //compile("junk")   // tragically, does not fail the test, i.e., arg must not be totally borked
+
       //dynamics,postfixOps,reflectiveCalls,implicitConversions,higherKinds,existentials,experimental.macros
       compile(s"-language:$all")
     }