Fix adjustDelta logic in adjustDeps

Author: odersky

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

@@ -331,39 +331,40 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
      *  and/or prefix of `bound`, just add the new parts of `bound`.
      *  @param  isLower `bound` and `prevBound` are lower bounds
      */
-    def adjustDelta(bound: Type, prevBound: Type, isLower: Boolean): Boolean =
-      if bound eq prevBound then true
+    def adjustDelta(bound: Type, prevBound: Type, isLower: Boolean, baseCase: => Boolean): Boolean =
+      if bound eq prevBound then
+        baseCase
       else bound match
         case bound: AndOrType =>
-          adjustDelta(bound.tp1, prevBound, isLower) && {
+          adjustDelta(bound.tp1, prevBound, isLower, baseCase) && {
             adjustReferenced(bound.tp2, isLower, add = true)
             true
           }
         case _ => false
 
-    /** Adjust dependencies to account for the delta of previous bound `prevBound`
-     *  and new bound `bound`.
-     *  @param  isLower `bound` and `prevBound` are lower bounds
+    /** Adjust dependencies to account for the delta of previous bounds `prevBounds`
+     *  and new bounds `bounds`.
+     *  @param add     true if the bounds are added, false if they are removed
      */
-    def adjustBounds(bound: Type, prevBound: Type, isLower: Boolean) =
-      if !adjustDelta(bound, prevBound, isLower) then
-        adjustReferenced(prevBound, isLower, add = false)
-        adjustReferenced(bound, isLower, add = true)
+    def adjustBounds(bounds: TypeBounds, add: Boolean) =
+      adjustReferenced(bounds.lo, isLower = true, add)
+      adjustReferenced(bounds.hi, isLower = false, add)
 
     entry match
-      case TypeBounds(lo, hi) =>
+      case entry @ TypeBounds(lo, hi) =>
         prevEntry match
-          case TypeBounds(plo, phi) =>
-            adjustBounds(lo, plo, isLower = true)
-            adjustBounds(hi, phi, isLower = false)
+          case prevEntry @ TypeBounds(plo, phi) =>
+            if !adjustDelta(lo, plo, isLower = true,
+                  adjustDelta(hi, phi, isLower = false, true))
+            then
+              adjustBounds(prevEntry, add = false)
+              adjustBounds(entry, add = true)
           case _ =>
-            adjustReferenced(lo, isLower = true, add = true)
-            adjustReferenced(hi, isLower = false, add = true)
+            adjustBounds(entry, add = true)
       case _ =>
         prevEntry match
-          case TypeBounds(plo, phi) =>
-            adjustReferenced(plo, isLower = true, add = false)
-            adjustReferenced(phi, isLower = false, add = false)
+          case prevEntry: TypeBounds =>
+            adjustBounds(prevEntry, add = false)
           case _ =>
         dropDeps(srcParam)
     this
@@ -608,7 +609,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
     boundsLens.update(this, current, param, newEntry).adjustDeps(newEntry, oldEntry, param)
 
   private def updateEntry(current: This, param: TypeParamRef, newEntry: Type)(using Context): This = {
-    //println(i"update $param to $tp in $current")
+    //println(i"update $param to $newEntry in $current")
     if Config.checkNoWildcardsInConstraint then assert(!newEntry.containsWildcardTypes)
     var current1 = updateEntryNoOrdering(current, param, newEntry, current.entry(param))
     newEntry match {