Tidy the code according to the feedback

Author: pdvrieze

core/api/kotlinx-serialization-core.klib.api

@@ -1173,7 +1173,7 @@ final inline fun (kotlinx.serialization.encoding/Encoder).kotlinx.serialization.
 final inline fun (kotlinx.serialization.encoding/Encoder).kotlinx.serialization.encoding/encodeStructure(kotlinx.serialization.descriptors/SerialDescriptor, crossinline kotlin/Function1<kotlinx.serialization.encoding/CompositeEncoder, kotlin/Unit>) // kotlinx.serialization.encoding/encodeStructure|encodeStructure@kotlinx.serialization.encoding.Encoder(kotlinx.serialization.descriptors.SerialDescriptor;kotlin.Function1<kotlinx.serialization.encoding.CompositeEncoder,kotlin.Unit>){}[0]
 final inline fun <#A: kotlin/Any, #B: reified #A> (kotlinx.serialization.modules/PolymorphicModuleBuilder<#A>).kotlinx.serialization.modules/subclass(kotlin.reflect/KClass<#B>) // kotlinx.serialization.modules/subclass|subclass@kotlinx.serialization.modules.PolymorphicModuleBuilder<0:0>(kotlin.reflect.KClass<0:1>){0§<kotlin.Any>;1§<0:0>}[0]
 final inline fun <#A: kotlin/Any, #B: reified #A> (kotlinx.serialization.modules/PolymorphicModuleBuilder<#A>).kotlinx.serialization.modules/subclass(kotlinx.serialization/KSerializer<#B>) // kotlinx.serialization.modules/subclass|subclass@kotlinx.serialization.modules.PolymorphicModuleBuilder<0:0>(kotlinx.serialization.KSerializer<0:1>){0§<kotlin.Any>;1§<0:0>}[0]
-final inline fun <#A: kotlin/Any, #B: reified #A> (kotlinx.serialization.modules/PolymorphicModuleBuilder<#A>).kotlinx.serialization.modules/subclassesOfSealed(kotlin.reflect/KClass<#B>) // kotlinx.serialization.modules/subclassesOfSealed|subclassesOfSealed@kotlinx.serialization.modules.PolymorphicModuleBuilder<0:0>(kotlin.reflect.KClass<0:1>){0§<kotlin.Any>;1§<0:0>}[0]
+final inline fun <#A: kotlin/Any, #B: reified #A> (kotlinx.serialization.modules/PolymorphicModuleBuilder<#A>).kotlinx.serialization.modules/subclassesOfSealed() // kotlinx.serialization.modules/subclassesOfSealed|subclassesOfSealed@kotlinx.serialization.modules.PolymorphicModuleBuilder<0:0>(){0§<kotlin.Any>;1§<0:0>}[0]
 final inline fun <#A: kotlin/Any> (kotlinx.serialization.modules/SerializersModuleBuilder).kotlinx.serialization.modules/polymorphic(kotlin.reflect/KClass<#A>, kotlinx.serialization/KSerializer<#A>? = ..., kotlin/Function1<kotlinx.serialization.modules/PolymorphicModuleBuilder<#A>, kotlin/Unit> = ...) // kotlinx.serialization.modules/polymorphic|polymorphic@kotlinx.serialization.modules.SerializersModuleBuilder(kotlin.reflect.KClass<0:0>;kotlinx.serialization.KSerializer<0:0>?;kotlin.Function1<kotlinx.serialization.modules.PolymorphicModuleBuilder<0:0>,kotlin.Unit>){0§<kotlin.Any>}[0]
 final inline fun <#A: kotlin/Any?> (kotlinx.serialization.encoding/Decoder).kotlinx.serialization.encoding/decodeStructure(kotlinx.serialization.descriptors/SerialDescriptor, crossinline kotlin/Function1<kotlinx.serialization.encoding/CompositeDecoder, #A>): #A // kotlinx.serialization.encoding/decodeStructure|decodeStructure@kotlinx.serialization.encoding.Decoder(kotlinx.serialization.descriptors.SerialDescriptor;kotlin.Function1<kotlinx.serialization.encoding.CompositeDecoder,0:0>){0§<kotlin.Any?>}[0]
 final inline fun <#A: kotlin/Any?> (kotlinx.serialization.encoding/Encoder).kotlinx.serialization.encoding/encodeCollection(kotlinx.serialization.descriptors/SerialDescriptor, kotlin.collections/Collection<#A>, crossinline kotlin/Function3<kotlinx.serialization.encoding/CompositeEncoder, kotlin/Int, #A, kotlin/Unit>) // kotlinx.serialization.encoding/encodeCollection|encodeCollection@kotlinx.serialization.encoding.Encoder(kotlinx.serialization.descriptors.SerialDescriptor;kotlin.collections.Collection<0:0>;kotlin.Function3<kotlinx.serialization.encoding.CompositeEncoder,kotlin.Int,0:0,kotlin.Unit>){0§<kotlin.Any?>}[0]

core/commonMain/src/kotlinx/serialization/modules/PolymorphicModuleBuilder.kt

@@ -26,9 +26,13 @@ public class PolymorphicModuleBuilder<in Base : Any> @PublishedApi internal cons
 
 
     /**
-     * Registers the child serializers for the sealed [subclass] [serializer] in the resulting module under
+     * Registers the child serializers for the sealed  type [T] in the resulting module under
      * the [base class][Base]. Please note that type `T` has to be sealed and have a standard serializer, if not a runtime error will
-     * be thrown at registration time. This function is a convenience function for the version that
+     * be thrown at registration time. If one of [T]'s subclasses is a sealed serializable class on
+     * its own, its subclasses are registered recursively as well. If one of [T]'s subclasses is an
+     * open polymorphic class an [IllegalArgumentException] is thrown.
+     *
+     * This function is a convenience function for the version that
      * receives a serializer.
      *
      *
@@ -37,7 +41,7 @@ public class PolymorphicModuleBuilder<in Base : Any> @PublishedApi internal cons
      * interface Base
      *
      * @Serializable
-     * sealed interface Sub
+     * sealed interface Sub: Base
      *
      * @Serializable
      * class Sub1: Sub
@@ -55,15 +59,18 @@ public class PolymorphicModuleBuilder<in Base : Any> @PublishedApi internal cons
 
 
     /**
-     * Registers the subclasses of the given class as subclasses of the outer class. This currently
-     * requires `serializer` to be sealed. If not a runtime error will be thrown at registration time.
+     * Registers the child serializers for the sealed  type [T] in the resulting module under
+     * the [base class][Base]. Please note that type `T` has to be sealed and have a standard serializer, if not a runtime error will
+     * be thrown at registration time. If one of [T]'s subclasses is a sealed serializable class on
+     * its own, its subclasses are registered recursively as well. If one of [T]'s subclasses is an
+     * open polymorphic class an [IllegalArgumentException] is thrown.
      *
      * Example:
      * ```kotlin
      * interface Base
      *
      * @Serializable
-     * sealed interface Sub
+     * sealed interface Sub: Base
      *
      * @Serializable
      * class Sub1: Sub
@@ -195,5 +202,5 @@ public inline fun <Base : Any, reified T : Base> PolymorphicModuleBuilder<Base>.
  * Registers the child serializers for the sealed class [T] in the resulting module under the [base class][Base].
  */
 @ExperimentalSerializationApi
-public inline fun <Base : Any, reified T : Base> PolymorphicModuleBuilder<Base>.subclassesOfSealed(clazz: KClass<T>): Unit =
-    subclassesOfSealed(clazz.serializer())
+public inline fun <Base : Any, reified T : Base> PolymorphicModuleBuilder<Base>.subclassesOfSealed(): Unit =
+    subclassesOfSealed(serializer<T>())

formats/json-tests/commonTest/src/kotlinx/serialization/features/PolymorphicSealedChildTest.kt

@@ -75,20 +75,10 @@ class PolymorphicSealedChildTest {
                 serializersModule = SerializersModule {
                     polymorphic(FooBase::class) {
                         subclassesOfSealed<FooOpen>()
-                        fail("This code should be unreachable as the previous operation fails")
-                        subclass(FooOpen.BazChild1::class)
-                        subclass(FooOpen.BazChild2::class)
                     }
                 }
             }
 
-            fail("Unreachable code that would represent the usage if valid (which is isn't per policy)")
-            assertStringFormAndRestored(
-                """{"someMetadata":43,"payload":[{"type":"BazOC1","baz":"aaa"}]}""",
-                FooHolder(43,listOf(FooOpen.BazChild1("aaa"))),
-                FooHolder.serializer(),
-                openJson
-            )
         }
         assertContains(assertNotNull(e.message), "FooOpen", )
         assertContains(assertNotNull(e.message), "incomplete hierarchy", )