[K/N] Added couple of reproducers for KT-57791

kotlin-native/backend.native/tests/framework/kt57791/knlibrary.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2023 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.
+ */
+
+interface Foo {
+    fun bar(): String?
+}
+
+internal class FooImplUnused : Foo {
+    override fun bar(): String? = null
+}
+
+fun foobar(foo: Foo): Boolean {
+    val s = foo.bar()
+    if (s == null)
+        return false
+    return s == "zzz"
+}

kotlin-native/backend.native/tests/framework/kt57791/test.swift

@@ -0,0 +1,21 @@
+import Foundation
+import Kt57791
+
+class FooImpl : Foo {
+    func bar() -> String? { "zzz" }
+}
+
+func testKt57791() throws {
+    try assertTrue(KnlibraryKt.foobar(foo: FooImpl()))
+}
+
+class TestTests : TestProvider {
+    var tests: [TestCase] = []
+
+    init() {
+        providers.append(self)
+        tests = [
+            TestCase(name: "Kt57791", method: withAutorelease(testKt57791)),
+        ]
+    }
+}