Revert to previous subsumes scheme

Add the path cases without changing the whole logic

Author: odersky

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

@@ -93,100 +93,42 @@ trait CaptureRef extends TypeProxy, ValueType:
   final def invalidateCaches() =
     myCaptureSetRunId = NoRunId
 
+  /** x subsumes x
+   *   this subsumes this.f
+   *   x subsumes y  ==>  x* subsumes y, x subsumes y?
+   *   x subsumes y  ==>  x* subsumes y*, x? subsumes y?
+   *   x: x1.type /\ x1 subsumes y  ==>  x subsumes y
+   *   TODO: Document path cases
+   */
   final def subsumes(y: CaptureRef)(using Context): Boolean =
-    val was = subsumesOld(y)
-    val now = subsumesNew(y)
-    if was != now then
-      println(i"diff for  $this subsumes $y, now: $now, ${this.getClass}, ${y.getClass}")
-    was
-
-  final def subsumesOld(y: CaptureRef)(using Context): Boolean =
     (this eq y)
     || this.isRootCapability
     || y.match
         case y: TermRef =>
             y.prefix.match
               case ypre: CaptureRef =>
-                this.subsumesOld(ypre)
+                this.subsumes(ypre)
                 || this.match
                     case x @ TermRef(xpre: CaptureRef, _) =>
                       x.symbol == y.symbol && xpre =:= ypre
                     case _ =>
                       false
               case _ => false
           || y.info.match
-              case y1: SingletonCaptureRef => this.subsumesOld(y1)
+              case y1: SingletonCaptureRef => this.subsumes(y1)
               case _ => false
-        case MaybeCapability(y1) => this.stripMaybe.subsumesOld(y1)
+        case MaybeCapability(y1) => this.stripMaybe.subsumes(y1)
         case _ => false
     || this.match
-        case ReachCapability(x1) => x1.subsumesOld(y.stripReach)
+        case ReachCapability(x1) => x1.subsumes(y.stripReach)
         case x: TermRef =>
           x.info match
-            case x1: SingletonCaptureRef => x1.subsumesOld(y)
+            case x1: SingletonCaptureRef => x1.subsumes(y)
             case _ => false
         case x: TermParamRef => subsumesExistentially(x, y)
         case x: TypeRef => assumedContainsOf(x).contains(y)
         case _ => false
 
-  /** x subsumes x
-   *   this subsumes this.f
-   *   x subsumes y  ==>  x* subsumes y, x subsumes y?
-   *   x subsumes y  ==>  x* subsumes y*, x? subsumes y?
-   *   x: x1.type /\ x1 subsumes y  ==>  x subsumes y
-   */
-  final def subsumesNew(y: CaptureRef)(using Context): Boolean =
-    def compareCaptureRefs(x: Type, y: Type): Boolean =
-      (x eq y)
-      || y.match
-          case y: CaptureRef => x.match
-            case x: CaptureRef => x.subsumesNew(y)
-            case _ => false
-          case _ => false
-
-    def compareUndelying(x: Type): Boolean = x match
-      case x: SingletonCaptureRef => x.subsumesNew(y)
-      case x: AndType => compareUndelying(x.tp1) || compareUndelying(x.tp2)
-      case x: OrType => compareUndelying(x.tp1) && compareUndelying(x.tp2)
-      case _ => false
-
-    if (this eq y) || this.isRootCapability then return true
-
-    // similar to compareNamed in TypeComparer
-    y match
-      case y: TermRef =>
-        this match
-          case x: TermRef =>
-            val xSym = x.symbol
-            val ySym = y.symbol
-
-            // check x.f and y.f
-            if (xSym ne NoSymbol)
-                && (xSym eq ySym)
-                && compareCaptureRefs(x.prefix, y.prefix)
-              || (x.name eq y.name)
-                && x.isPrefixDependentMemberRef
-                && compareCaptureRefs(x.prefix, y.prefix)
-                && x.signature == y.signature
-                && !(xSym.isClass && ySym.isClass)
-            then return true
-          case _ =>
-
-        // shorten
-        if compareCaptureRefs(this, y.prefix) then return true
-        // underlying
-        if compareCaptureRefs(this, y.info) then return true
-      case MaybeCapability(y1) => return this.stripMaybe.subsumesNew(y1)
-      case _ =>
-
-    return this.match
-      case ReachCapability(x1) => x1.subsumesNew(y.stripReach)
-      case x: TermRef => compareUndelying(x.info)
-      case CapturingType(x1, _) => compareUndelying(x1)
-      case x: TermParamRef => subsumesExistentially(x, y)
-      case x: TypeRef => assumedContainsOf(x).contains(y)
-      case _ => false
-
   def assumedContainsOf(x: TypeRef)(using Context): SimpleIdentitySet[CaptureRef] =
     CaptureSet.assumedContains.getOrElse(x, SimpleIdentitySet.empty)