Add a test for dummy symbols

Author: noti0na1

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

@@ -652,22 +652,6 @@ trait FollowAliasesMap(using Context) extends TypeMap:
       else t
     else mapOver(t)
 
-/** An extractor for `caps.reachCapability(ref)`, which is used to express a reach
- *  capability as a tree in a @retains annotation.
- */
-// object ReachCapabilityApply:
-//   def unapply(tree: Apply)(using Context): Option[Tree] = tree match
-//     case Apply(reach, arg :: Nil) if reach.symbol == defn.Caps_reachCapability => Some(arg)
-//     case _ => None
-
-/** An extractor for `caps.readOnlyCapability(ref)`, which is used to express a read-only
- *  capability as a tree in a @retains annotation.
- */
-// object ReadOnlyCapabilityApply:
-//   def unapply(tree: Apply)(using Context): Option[Tree] = tree match
-//     case Apply(ro, arg :: Nil) if ro.symbol == defn.Caps_readOnlyCapability => Some(arg)
-//     case _ => None
-
 abstract class AnnotatedCapability(annotCls: Context ?=> ClassSymbol):
   def apply(tp: Type)(using Context): AnnotatedType =
     assert(tp.isTrackableRef, i"not a trackable ref: $tp")

compiler/src/dotty/tools/dotc/core/Flags.scala

@@ -451,7 +451,7 @@ object Flags {
 
   /** Flags representing source modifiers */
   private val CommonSourceModifierFlags: FlagSet =
-    commonFlags(Private, Protected, Final, Case, Implicit, Given, Override, JavaStatic, Transparent, Erased, CaptureParam)
+    commonFlags(Private, Protected, Final, Case, Implicit, Given, Override, JavaStatic, Transparent, Erased)
 
   val TypeSourceModifierFlags: FlagSet =
     CommonSourceModifierFlags.toTypeFlags | Abstract | Sealed | Opaque | Open

tests/neg-custom-args/captures/check-dummy-symbol.scala

@@ -0,0 +1,7 @@
+import language.experimental.captureChecking
+
+class A:
+  type C^
+
+def f(a: A): a.C = a.C // error
+def g[C^]: C = C // error