Make isExactlyNothing and isExactlyAny work for And/OrTypes

Might fix #24013.

Author: odersky

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

@@ -244,13 +244,21 @@ object Types extends TypeUtils {
     def isExactlyNothing(using Context): Boolean = this match {
       case tp: TypeRef =>
         tp.name == tpnme.Nothing && (tp.symbol eq defn.NothingClass)
+      case AndType(tp1, tp2) =>
+        tp1.isExactlyNothing || tp2.isExactlyNothing
+      case OrType(tp1, tp2) =>
+        tp1.isExactlyNothing && tp2.isExactlyNothing
       case _ => false
     }
 
     /** Is this type exactly Any (no vars, aliases, refinements etc allowed)? */
     def isExactlyAny(using Context): Boolean = this match {
       case tp: TypeRef =>
         tp.name == tpnme.Any && (tp.symbol eq defn.AnyClass)
+      case AndType(tp1, tp2) =>
+        tp1.isExactlyAny && tp2.isExactlyAny
+      case OrType(tp1, tp2) =>
+        tp1.isExactlyAny || tp2.isExactlyAny
       case _ => false
     }