Add missing case in maxSubsumes

Author: odersky

compiler/src/dotty/tools/dotc/cc/Capability.scala

@@ -698,6 +698,8 @@ object Capabilities:
             case _ =>
               y.derivesFromSharable
               || canAddHidden && vs != VarState.HardSeparate && CCState.capIsRoot
+        case Restricted(x1, cls) =>
+          y.isKnownClassifiedAs(cls) && x1.maxSubsumes(y, canAddHidden)
         case _ =>
           y match
             case ReadOnly(y1) => this.stripReadOnly.maxSubsumes(y1, canAddHidden)

tests/pos-custom-args/captures/restrict-subsumes.scala

@@ -0,0 +1,11 @@
+import caps.{cap, Classifier, Capability}
+
+trait Read extends Capability, Classifier
+
+trait A extends Read
+
+def weird(f: () ->{cap.only[Read]} Unit) = ???
+
+def test(x: A^) =
+  val g = () => println(x)
+  weird(g)