In replace, update param after updating dependent params

Author: odersky

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

@@ -594,6 +594,8 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
     val replacement = tp.dealiasKeepAnnots.stripTypeVar
     if param == replacement then this.checkWellFormed()
     else
+      assert(replacement.isValueTypeOrLambda)
+
       val droppedTypeVar = typeVarOfParam(param)
       //println(i"replace $param, $droppedTypeVar with $replacement in $this")
       val substParamAndDropTypeVar = new SubstParamMap(param, replacement):
@@ -603,13 +605,9 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
             replacement
           else super.apply(t)
 
-      assert(replacement.isValueTypeOrLambda)
-      var current =
-        if isRemovable(param.binder) then remove(param.binder)
-        else updateEntry(this, param, replacement)
+      var current = this
 
       def removeParam(ps: List[TypeParamRef]) = ps.filterConserve(param ne _)
-
       for lo <- lower(param) do
         current = upperLens.map(this, current, lo, removeParam)
       for hi <- upper(param) do
@@ -621,6 +619,10 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
         val newEntry = current.ensureNonCyclic(other, substParamAndDropTypeVar(oldEntry))
         current = updateEntryNoOrdering(current, other, newEntry, oldEntry)
       }
+
+      current =
+        if isRemovable(param.binder) then current.remove(param.binder)
+        else updateEntry(current, param, replacement)
       current.dropDeps(param)
       current.checkWellFormed()
   end replace