Fixes and polishings

Author: bracevac

tests/neg-custom-args/captures/capset-members4.scala

@@ -0,0 +1,27 @@
+import language.experimental.captureChecking
+import language.experimental.modularity
+import caps.*
+
+def test =
+  val x: Any^ = ???
+  val y: Any^ = ???
+  val z: Any^ = ???
+  def onlyWithZ[cap C](using c: Contains[C, z.type]) = ???
+
+  trait IncludesZ[cap C]:
+    val c: Contains[C, z.type]
+
+  trait Foo:
+    cap type C >: {x} <: {x,y,z} : IncludesZ
+
+  val foo: Foo = ???
+/*   new Foo {
+    override given IncludesZ[C]: // FIXME: doesn't work yet
+      val c: Contains[C, z.type] = summon
+    cap type C = {x,z}
+  } */
+  onlyWithZ(using foo.C.c)
+  onlyWithZ[{z}]
+  onlyWithZ[{x,z}]
+  onlyWithZ[{x,y,z}]
+  onlyWithZ[{x,y}] // error