Failing test

Author: odersky

tests/neg-custom-args/captures/box-unsoundness.scala

@@ -0,0 +1,13 @@
+//@annotation.capability
+class CanIO { def use(): Unit = () }
+def use[X](x: X): (op: X -> Unit) -> Unit = op => op(x)
+def test(io: CanIO^): Unit =
+  val f: (CanIO^ => Unit) -> Unit = use[CanIO^](io)  //
+  val _: (CanIO^ => Unit) -> Unit = f  // error
+
+  val g1 = () => f(x => x.use())  // error
+
+  val a1 = f(x => x.use())
+  val a2 = () => f(x => x.use())
+  val g2: () -> Unit = a2        // error
+  // was UNSOUND: g uses the capability io but has an empty capture set