[K/JS] fix(KT-46643): prevent removal of setter for overridden external field.

js/js.translator/testData/box/native/externalValWithOverridenVar.kt

@@ -0,0 +1,91 @@
+// KT-46643
+// IGNORE_BACKEND: WASM
+// WITH_STDLIB
+
+import kotlin.reflect.KProperty
+
+external interface IBase {
+    val foo: String
+}
+
+external abstract class Base : IBase
+
+open class A : Base() {
+    override var foo: String = "Error: A setter was not called."
+        set(k) { result = "O$k"}
+
+    lateinit var result: String
+}
+
+open class B : Base() {
+    override val foo: String = "OK"
+
+    open val result: String get() = foo
+}
+
+class C : B() {
+    override var foo: String = "Error: C setter was not called."
+        set(k) { result = "O$k"}
+
+    override lateinit var result: String
+}
+
+open class D : B() {
+    override val foo: String = "OK"
+}
+
+open class E : D() {
+    override var foo: String = "Error: E setter was not called."
+        set(k) { result = "O$k"}
+
+    override lateinit var result: String
+}
+
+open class F: B() {
+    override var foo: String by CustomDelegator
+
+    private object CustomDelegator {
+        operator fun getValue(thisRef: Any?, property: KProperty<*>): String {
+            return "Error: F setter was not called."
+        }
+
+        operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) {
+            result = "O$value"
+        }
+
+        lateinit var result: String
+    }
+
+    override val result: String get() = CustomDelegator.result
+}
+
+class G(val b: B): IBase by b {
+    val result: String get() = b.result
+}
+
+fun box(): String {
+    val a = A()
+    if (a.result != "OK") return a.foo
+
+    val b = B()
+    if (b.result != "OK") return b.foo
+
+    val c = C()
+    if (c.result != "OK") return c.foo
+
+    val d = D()
+    if (d.result != "OK") return d.foo
+
+    val e = E()
+    if (e.result != "OK") return e.foo
+
+    try {
+        val f = F()
+        return "Failed: it should not work for now, because of delegating objects initialization order"
+    } catch (e: Throwable) {}
+
+    val g = G(e)
+    if (g.result != "OK") return g.foo
+
+    return "OK"
+}