Merge pull request #14761 from dotty-staging/fix-14760

Keep correct kind when preparing constraint in stripParams

Author: odersky

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

@@ -248,7 +248,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
       NoType
     case tp: TypeBounds =>
       val lo1 = stripParams(tp.lo, todos, !isUpper).orElse(defn.NothingType)
-      val hi1 = stripParams(tp.hi, todos, isUpper).orElse(defn.AnyKindType)
+      val hi1 = stripParams(tp.hi, todos, isUpper).orElse(tp.topType)
       tp.derivedTypeBounds(lo1, hi1)
     case tp: AndType if isUpper =>
       val tp1 = stripParams(tp.tp1, todos, isUpper)

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

@@ -229,7 +229,11 @@ class TypeApplications(val self: Type) extends AnyVal {
       (alias ne self) && alias.hasSimpleKind
     }
 
-  /** The top type with the same kind as `self`. */
+  /** The top type with the same kind as `self`. This is largest type capturing
+   *  the parameter shape of a type without looking at precise bounds.
+   *    - The top-type of simple-kinded types is Any
+   *    - A kind like (* -> *) -> * is represented by the top type [X1 <: [X2] =>> Any] =>> Any
+   */
   def topType(using Context): Type =
     if self.hasSimpleKind then
       defn.AnyType

tests/pos/i14760.scala

@@ -0,0 +1,5 @@
+enum SUB[-A, +B]:
+  case Refl[X]() extends SUB[X, X]
+
+def foo[C, A >: C <: C, B](e: SUB[B, A]) = e match
+  case SUB.Refl() =>