Add comment for path-dependent limitation

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

@@ -494,10 +494,7 @@ class CheckCaptures extends Recheck, SymTransformer:
 
       val selType = recheckSelection(tree, qualType, name, disambiguate)
       val selWiden = selType.widen
-      def isStableSel = selType match
-        case selType: NamedType => selType.symbol.isStableMember
-        case _ => false
-
+
       if pt == LhsProto
           || qualType.isBoxedCapturing
           || selType.isTrackableRef

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

@@ -518,6 +518,11 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
           info match
             case mt: MethodOrPoly =>
               val psyms = psymss.head
+              // TODO: the substitution does not work for param-dependent method types.
+              // For example, `(x: T, y: x.f.type) => Unit`. In this case, when we
+              // substitute `x.f.type`, `x` becomes a `TermParamRef`. But the new method
+              // type is still under initialization and `paramInfos` is still `null`,
+              // so the new `NamedType` will not have a denoation.
               mt.companion(mt.paramNames)(
                 mt1 =>
                   if !paramSignatureChanges && !mt.isParamDependent && prevLambdas.isEmpty then

tests/neg-custom-args/captures/path-connection.scala

@@ -19,6 +19,8 @@ class ReaderProxy(tracked val r: Reader^) extends Reader:
 class SenderProxy(tracked val s: Sender^) extends Sender:
   def send(msg: String) = s.send("(Proxy) " + msg)
 
+// TODO: We have to put `c` in the different argument list to make it work.
+// See the comments in `integrateRT`.
 def testConnection(c: Connection^)(
     handle1: Reader^{c.readOnly} => String,
     handle2: Sender^{c} => Unit,