Drop references to replaced TypeVar in replace (2)

Author: odersky

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

@@ -11,6 +11,7 @@ import config.Config
 import config.Printers.constr
 import reflect.ClassTag
 import Constraint.ReverseDeps
+import Substituters.SubstParamMap
 import annotation.tailrec
 import annotation.internal.sharable
 import cc.{CapturingType, derivedCapturingType}
@@ -590,6 +591,15 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
     val replacement = tp.dealiasKeepAnnots.stripTypeVar
     if param == replacement then this.checkWellFormed()
     else
+      val droppedTypeVar = typeVarOfParam(param)
+      //println(i"replace $param, $droppedTypeVar with $replacement in $this")
+      val substParamAndDropTypeVar = new SubstParamMap(param, replacement):
+        override def apply(t: Type): Type =
+          if t eq droppedTypeVar then
+            //println(i"DROP $t")
+            replacement
+          else super.apply(t)
+
       assert(replacement.isValueTypeOrLambda)
       var current =
         if isRemovable(param.binder) then remove(param.binder)
@@ -609,11 +619,10 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
         current = lowerLens.map(this, current, hi, removeParam)
 
       current.foreachParam { (p, i) =>
-        current = boundsLens.map(this, current, p, i,
-          entry =>
-            val newEntry = replaceParam(entry, p, i)
-            adjustDeps(newEntry, entry, p.paramRefs(i))
-            newEntry)
+        val other = p.paramRefs(i)
+        val oldEntry = current.entry(other)
+        val newEntry = current.ensureNonCyclic(other, substParamAndDropTypeVar(oldEntry))
+        current = updateEntryNoOrdering(current, other, newEntry, oldEntry)
       }
       current.dropDeps(param)
       current.checkWellFormed()