Remove unused JvmTypeAliasExtensionVisitor and JvmValueParameterExtensionVisitor

They were added in e4702bf438 and a08cf59017 but in fact they are not
needed on JVM until there are JVM-specific extensions in the metadata.

Moreover, there was a typo in JvmValueParameterExtensionVisitor's
superclass (see https://github.com/JetBrains/kotlin/pull/4613).

libraries/kotlinx-metadata/jvm/ChangeLog.md

@@ -8,6 +8,7 @@
   - `JvmFlag.Class.HAS_METHOD_BODIES_IN_INTERFACE`
   - `JvmFlag.Class.IS_COMPILED_IN_COMPATIBILITY_MODE`
 - [`KT-48965`](https://youtrack.jetbrains.com/issue/KT-48965) Make the type of `KmValueParameter.type` non-null `KmType`
+- Remove unused `JvmTypeAliasExtensionVisitor` and `JvmValueParameterExtensionVisitor`
 
 ## 0.3.0
 

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/impl/JvmMetadataExtensions.kt

@@ -310,9 +310,9 @@ internal class JvmMetadataExtensions : MetadataExtensions {
 
     override fun createTypeExtension(): KmTypeExtension = JvmTypeExtension()
 
-    override fun createTypeAliasExtension(): KmTypeAliasExtension = JvmTypeAliasExtension()
+    override fun createTypeAliasExtension(): KmTypeAliasExtension? = null
 
-    override fun createValueParameterExtension(): KmValueParameterExtension = JvmValueParameterExtension()
+    override fun createValueParameterExtension(): KmValueParameterExtension? = null
 
     private fun JvmMemberSignature.toJvmMethodSignature(c: WriteContext): JvmProtoBuf.JvmMethodSignature =
         JvmProtoBuf.JvmMethodSignature.newBuilder().apply {

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/impl/jvmExtensionNodes.kt

@@ -188,17 +188,3 @@ internal class JvmTypeExtension : JvmTypeExtensionVisitor(), KmTypeExtension {
         visitor.visitEnd()
     }
 }
-
-internal class JvmTypeAliasExtension : JvmTypeAliasExtensionVisitor(), KmTypeAliasExtension {
-    override fun accept(visitor: KmTypeAliasExtensionVisitor) {
-        require(visitor is JvmTypeAliasExtensionVisitor)
-        visitor.visitEnd()
-    }
-}
-
-internal class JvmValueParameterExtension : JvmValueParameterExtensionVisitor(), KmValueParameterExtension {
-    override fun accept(visitor: KmValueParameterExtensionVisitor) {
-        require(visitor is JvmValueParameterExtensionVisitor)
-        visitor.visitEnd()
-    }
-}

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/jvmExtensionVisitors.kt

@@ -368,57 +368,3 @@ open class JvmTypeExtensionVisitor @JvmOverloads constructor(
         const val PLATFORM_TYPE_ID = JvmProtoBufUtil.PLATFORM_TYPE_ID
     }
 }
-
-/**
- * A visitor to visit JVM extensions for a type alias.
- */
-open class JvmTypeAliasExtensionVisitor @JvmOverloads constructor(
-    private val delegate: JvmTypeAliasExtensionVisitor? = null
-) : KmTypeAliasExtensionVisitor {
-    final override val type: KmExtensionType
-        get() = TYPE
-
-    /**
-     * Visits the end of JVM extensions for the type alias.
-     */
-    open fun visitEnd() {
-        delegate?.visitEnd()
-    }
-
-    companion object {
-        /**
-         * The type of this extension visitor.
-         *
-         * @see KmExtensionType
-         */
-        @JvmField
-        val TYPE: KmExtensionType = KmExtensionType(JvmTypeAliasExtensionVisitor::class)
-    }
-}
-
-/**
- * A visitor to visit JVM extensions for a value parameter.
- */
-open class JvmValueParameterExtensionVisitor @JvmOverloads constructor(
-    private val delegate: JvmValueParameterExtensionVisitor? = null
-) : KmTypeAliasExtensionVisitor {
-    final override val type: KmExtensionType
-        get() = TYPE
-
-    /**
-     * Visits the end of JVM extensions for the value parameter.
-     */
-    open fun visitEnd() {
-        delegate?.visitEnd()
-    }
-
-    companion object {
-        /**
-         * The type of this extension visitor.
-         *
-         * @see KmExtensionType
-         */
-        @JvmField
-        val TYPE: KmExtensionType = KmExtensionType(JvmValueParameterExtensionVisitor::class)
-    }
-}

libraries/kotlinx-metadata/src/kotlinx/metadata/impl/extensions/MetadataExtensions.kt

@@ -76,9 +76,9 @@ interface MetadataExtensions {
 
     fun createTypeExtension(): KmTypeExtension
 
-    fun createTypeAliasExtension(): KmTypeAliasExtension
+    fun createTypeAliasExtension(): KmTypeAliasExtension?
 
-    fun createValueParameterExtension(): KmValueParameterExtension
+    fun createValueParameterExtension(): KmValueParameterExtension?
 
     companion object {
         val INSTANCES: List<MetadataExtensions> by lazy {

libraries/kotlinx-metadata/src/kotlinx/metadata/nodes.kt

@@ -536,7 +536,7 @@ class KmTypeAlias(
     val versionRequirements: MutableList<KmVersionRequirement> = ArrayList(0)
 
     private val extensions: List<KmTypeAliasExtension> =
-        MetadataExtensions.INSTANCES.map(MetadataExtensions::createTypeAliasExtension)
+        MetadataExtensions.INSTANCES.mapNotNull(MetadataExtensions::createTypeAliasExtension)
 
     override fun visitTypeParameter(flags: Flags, name: String, id: Int, variance: KmVariance): KmTypeParameterVisitor =
         KmTypeParameter(flags, name, id, variance).addTo(typeParameters)
@@ -594,7 +594,7 @@ class KmValueParameter(
     var varargElementType: KmType? = null
 
     private val extensions: List<KmValueParameterExtension> =
-        MetadataExtensions.INSTANCES.map(MetadataExtensions::createValueParameterExtension)
+        MetadataExtensions.INSTANCES.mapNotNull(MetadataExtensions::createValueParameterExtension)
 
     override fun visitType(flags: Flags): KmTypeVisitor =
         KmType(flags).also { type = it }