Add IO test

tests/neg-custom-args/captures/io.scala

@@ -0,0 +1,21 @@
+sealed trait IO:
+ def puts(msg: Any): Unit = println(msg)
+
+def test1 =
+ val IO : IO retains * = new IO {}
+ def foo = IO.puts("hello")
+ val x : () => Unit = () => foo // error: Found: (() => Unit) retains IO; Required: () => Unit
+
+def test2 =
+ val IO : IO retains * = new IO {}
+ def puts(msg: Any, io: IO retains *) = println(msg)
+ def foo() = puts("hello", IO)
+ val x : () => Unit = () => foo() // error: Found: (() => Unit) retains IO; Required: () => Unit
+
+type Capability[T] = T retains *
+
+def test3 =
+ val IO : Capability[IO] = new IO {}
+ def puts(msg: Any, io: Capability[IO]) = println(msg)
+ def foo() = puts("hello", IO)
+ val x : () => Unit = () => foo() // error: Found: (() => Unit) retains IO; Required: () => Unit