Fix levelOwner docs and logic

Also: Drop RefiningVar

Author: odersky

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

@@ -423,9 +423,7 @@ extension (sym: Symbol)
     || sym.is(Method, butNot = Accessor)
 
   /** The owner of the current level. Qualifying owners are
-   *   - methods other than constructors and anonymous functions
-   *   - anonymous functions, provided they either define a local
-   *     root of type caps.Capability, or they are the rhs of a val definition.
+   *   - methods, other than accessors
    *   - classes, if they are not staticOwners
    *   - _root_
    */

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

@@ -520,9 +520,7 @@ object CaptureSet:
       if elem.isRootCapability then !noUniversal
       else elem match
         case elem: TermRef if levelLimit.exists =>
-          var sym = elem.symbol
-          if sym.isLevelOwner then sym = sym.owner
-          levelLimit.isContainedIn(sym.levelOwner)
+          levelLimit.isContainedIn(elem.symbol.levelOwner)
         case elem: ThisType if levelLimit.exists =>
           levelLimit.isContainedIn(elem.cls.levelOwner)
         case ReachCapability(elem1) =>
@@ -622,13 +620,6 @@ object CaptureSet:
     override def toString = s"Var$id$elems"
   end Var
 
-  /** Variables that represent refinements of class parameters can have the universal
-   *  capture set, since they represent only what is the result of the constructor.
-   *  Test case: Without that tweak, logger.scala would not compile.
-   */
-  class RefiningVar(directOwner: Symbol)(using Context) extends Var(directOwner):
-    override def disallowRootCapability(handler: () => Context ?=> Unit)(using Context) = this
-
   /** A variable that is derived from some other variable via a map or filter. */
   abstract class DerivedVar(owner: Symbol, initialElems: Refs)(using @constructorOnly ctx: Context)
   extends Var(owner, initialElems):

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

@@ -189,7 +189,10 @@ class Setup extends PreRecheck, SymTransformer, SetupAPI:
                   val getterType =
                     mapInferred(refine = false)(tp.memberInfo(getter)).strippedDealias
                   RefinedType(core, getter.name,
-                      CapturingType(getterType, CaptureSet.RefiningVar(ctx.owner)))
+                      CapturingType(getterType,
+                      new CaptureSet.Var(ctx.owner):
+                        override def disallowRootCapability(handler: () => Context ?=> Unit)(using Context) = this
+                      ))
                     .showing(i"add capture refinement $tp --> $result", capt)
                 else
                   core