Add test for SI-9010

This is extremely ugly (not only does it use reflection, is uses Java
reflection with hard-coded mangled symbol name because of a bug in Scala
reflection), but I don't know of a better solution.  :-(

Author: liskin

src/test/scala/scala/util/parsing/combinator/t9010.scala

@@ -0,0 +1,51 @@
+import scala.util.parsing.combinator._
+import scala.util.DynamicVariable
+
+import org.junit.Test
+
+class t9010 {
+  @Test
+  def test: Unit = {
+    val p = new grammar
+    val lastNoSuccessVar = getLastNoSuccessVar(p)
+    import p._
+
+    val res1 = parse(x, "x")
+    assert(res1.successful)
+    assert(lastNoSuccessVar.value == None)
+
+    val res2 = parse(x, "y")
+    assert(!res2.successful)
+    assert(lastNoSuccessVar.value == None)
+
+    val res3 = parseAll(x, "x")
+    assert(res3.successful)
+    assert(lastNoSuccessVar.value == None)
+
+    val res4 = parseAll(x, "y")
+    assert(!res4.successful)
+    assert(lastNoSuccessVar.value == None)
+  }
+
+  private def getLastNoSuccessVar(p: Parsers): DynamicVariable[Option[_]] = {
+    // use java reflection instead of scala (see below) because of
+    // https://issues.scala-lang.org/browse/SI-9306
+    val fn = "scala$util$parsing$combinator$Parsers$$lastNoSuccessVar"
+    val f = p.getClass.getDeclaredMethod(fn)
+    f.setAccessible(true)
+    f.invoke(p).asInstanceOf[DynamicVariable[Option[_]]]
+
+    /*
+    val ru = scala.reflect.runtime.universe
+    val mirror = ru.runtimeMirror(getClass.getClassLoader)
+    val lastNoSuccessVarField =
+      ru.typeOf[Parsers].decl(ru.TermName("lastNoSuccessVar")).asTerm.accessed.asTerm
+    mirror.reflect(p).reflectField(lastNoSuccessVarField).get.
+      asInstanceOf[DynamicVariable[Option[_]]]
+    */
+  }
+
+  private final class grammar extends RegexParsers {
+    val x: Parser[String] = "x"
+  }
+}