More efficient default value evaluator

Author: plokhotnyuk

core/src/main/scala/magnolia1/impl.scala

@@ -111,10 +111,18 @@ object CaseClassDerivation:
         val label = constValue[l].asInstanceOf[String]
         val tc = new SerializableFunction0[Typeclass[p]]:
           override def apply(): Typeclass[p] = summonInline[Typeclass[p]]
-
-        val d = new SerializableFunction0[Option[p]]:
-          private def unsafeCast(any: Any) = Option.when(any == null || (any: @unchecked).isInstanceOf[p])(any.asInstanceOf[p])
-          override def apply(): Option[p] = defaults.get(label).flatten.flatMap(d => unsafeCast(d.apply))
+        val evaluator: () => Any = defaults(label).orNull
+        val d =
+          if (evaluator ne null) {
+            new SerializableFunction0[Option[p]]:
+              override def apply(): Option[p] =
+                val v = evaluator()
+                if (v.isInstanceOf[p]) Some(v.asInstanceOf[p])
+                else None
+          } else {
+            new SerializableFunction0[Option[p]]:
+              override def apply(): Option[p] = None
+          }
         paramFromMaps[Typeclass, A, p](
           label,
           CallByNeed.createLazy(tc),