Polish and comment Setup class

Author: odersky

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

@@ -592,6 +592,7 @@ extension (sym: Symbol)
     && !defn.isPolymorphicAfterErasure(sym)
     && !defn.isTypeTestOrCast(sym)
 
+  /** It's a parameter accessor that is not annotated @constructorOnly or @uncheckedCaptures */
   def isRefiningParamAccessor(using Context): Boolean =
     sym.is(ParamAccessor)
     && {

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

@@ -337,6 +337,7 @@ object Existential:
     if needsWrap then wrapped else tp
   end mapCap
 
+  /** Map `cap` in function results to fresh existentials */
   def mapCapInResults(fail: Message => Unit)(using Context): TypeMap = new:
 
     def mapFunOrMethod(tp: Type, args: List[Type], res: Type): Type =