Fix unbox

Author: timsueberkrueb

effekt/jvm/src/test/scala/effekt/core/NewNormalizerTests.scala

@@ -124,16 +124,15 @@ class NewNormalizerTests extends CoreTests {
   // This example shows a box that contains an extern reference.
   // The normalizer is able to unbox this indirection away.
   test("extern in box") {
-    val input =
-    """
+    val input = """
         |extern def foo: Int = vm"42"
         |
         |def run(): Int = {
         |    val f = box {
-        |      foo
+        |      box foo
         |    } at { io }
         |
-        |    val x = unbox f()()
+        |    val x = /* unbox */ f()()
         |    return x
         |}
         |

effekt/shared/src/main/scala/effekt/core/Parser.scala

@@ -91,6 +91,7 @@ class EffektLexers extends Parsers {
   lazy val `at` = keyword("at")
   lazy val `in` = keyword("in")
   lazy val `box` = keyword("box")
+  lazy val `unbox` = keyword("unbox")
   lazy val `return` = keyword("return")
   lazy val `region` = keyword("region")
   lazy val `resource` = keyword("resource")
@@ -381,6 +382,7 @@ class CoreParsers(names: Names) extends EffektLexers {
   // ------
   lazy val block: P[Block] =
     ( blockVar
+    | `unbox` ~> expr ^^ Block.Unbox.apply
     | `new` ~> implementation ^^ Block.New.apply
     | blockLit
     // TODO check left associative nesting (also for select)