[WasmJs] Add support for external class reflection

Fix #KT-64890

libraries/stdlib/wasm/js/src/kotlin/reflect/KExternalClassImpl.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.wasm.internal
+
+import kotlin.reflect.*
+
+@Suppress("UNUSED_PARAMETER")
+private fun getJsClassName(jsKlass: JsAny): String? =
+    js("jsKlass.name")
+
+@Suppress("UNUSED_PARAMETER")
+private fun instanceOf(ref: JsAny, jsKlass: JsAny): Boolean =
+    js("ref instanceof jsKlass")
+
+internal class KExternalClassImpl<T : Any> @WasmPrimitiveConstructor constructor(private val jsConstructor: JsAny) : KClass<T> {
+    override val simpleName: String? get() = getJsClassName(jsConstructor)
+    override val qualifiedName: String? get() = null
+
+    override fun isInstance(value: Any?): Boolean =
+        value is JsExternalBox && instanceOf(value.ref, jsConstructor)
+
+    override fun equals(other: Any?): Boolean =
+        other is KExternalClassImpl<*> && jsConstructor == other.jsConstructor
+
+    override fun hashCode(): Int = simpleName.hashCode()
+
+    override fun toString(): String = "class $simpleName"
+}

libraries/stdlib/wasm/js/src/kotlin/reflect/reflection.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package kotlin.wasm.internal
+
+import kotlin.reflect.*
+
+@Suppress("UNUSED_PARAMETER")
+private fun getConstructor(obj: JsAny): JsAny? =
+    js("obj.constructor")
+
+@Suppress("UNCHECKED_CAST")
+internal actual fun <T : Any> getKClassForObject(obj: Any): KClass<T> {
+    if (obj !is JsExternalBox) return KClassImpl(getTypeInfoTypeDataByPtr(obj.typeInfo))
+    val jsConstructor = getConstructor(obj.ref) ?: error("JavaScript constructor is not defined")
+    return KExternalClassImpl(jsConstructor)
+}