Fix tests

Author: noti0na1

Diff for: tests/neg/cc-poly-2.check

@@ -1,10 +1,3 @@
--- [E007] Type Mismatch Error: tests/neg/cc-poly-2.scala:13:15 ---------------------------------------------------------
-13 |    f[Nothing](d) // error
-   |               ^
-   |               Found:    (d : Test.D^)
-   |               Required: Test.D
-   |
-   | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg/cc-poly-2.scala:14:19 ---------------------------------------------------------
 14 |    f[CapSet^{c1}](d) // error
    |                   ^

Diff for: tests/neg/cc-poly-2.scala

@@ -10,7 +10,7 @@ object Test:
 
   def test(c1: C, c2: C) =
     val d: D^ = D()
-    f[Nothing](d) // error
+    // f[Nothing](d) // already rule out at typer
     f[CapSet^{c1}](d) // error
     val x = f(d)
     val _: D^{c1} = x // error

Diff for: tests/pos/cc-poly-source-capability.scala

@@ -20,13 +20,14 @@ import caps.unbox
 
   def test1(async1: Async, @unbox others: List[Async]) =
     val src = Source[CapSet^{async1, others*}]
+    val _: Set[Listener^{async1, others*}] = src.allListeners
     val lst1 = listener(async1)
     val lsts = others.map(listener)
     val _: List[Listener^{others*}] = lsts
     src.register{lst1}
     src.register(listener(async1))
-    lsts.foreach(src.register)
-    others.map(listener).foreach(src.register)
+    lsts.foreach(src.register(_)) // TODO: why we need to use _ explicitly here?
+    others.map(listener).foreach(src.register(_))
     val ls = src.allListeners
     val _: Set[Listener^{async1, others*}] = ls