[WASM] throwableExtensions implementation

libraries/stdlib/wasm/builtins/kotlin/Throwable.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2022 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
+
+import kotlin.wasm.internal.ExternalInterfaceType
+import kotlin.wasm.internal.jsToKotlinStringAdapter
+
+/**
+ * The base class for all errors and exceptions. Only instances of this class can be thrown or caught.
+ *
+ * @param message the detail message string.
+ * @param cause the cause of this throwable.
+ */
+public open class Throwable(open val message: String?, open val cause: kotlin.Throwable?) {
+    constructor(message: String?) : this(message, null)
+
+    constructor(cause: Throwable?) : this(cause?.toString(), cause)
+
+    constructor() : this(null, null)
+
+    private val jsStack: ExternalInterfaceType = captureStackTrace()
+
+    internal val stack: String by lazy {
+        jsToKotlinStringAdapter(jsStack).removePrefix("Error\n")
+    }
+
+    internal var suppressedExceptionsList: MutableList<Throwable>? = null
+}
+
+@JsFun("() => new Error().stack")
+private external fun captureStackTrace(): ExternalInterfaceType