[Kotlin] Get rid of Kotlin generated check — “null cannot be cast to non-null type”

Use case 1:

The code below is to cast (as) a nullable variable:

data class Boss(val name: String)

data class Staff(val name: String)

fun getPerson(type: String, name: String): Any? {
    return when (type) {
        "boss" -> Boss(name)
        "staff" -> Staff(name)
        else -> null
    }
}
fun main() {
    val boss = getPerson("boss", "Peter") as Boss
    print(boss)
}

Highlighted points:

1. getPerson() might return null
2. Boss and Staff are supposed to be obfuscated and no clues in getPerson()

Let’s look at the decompiled code below:

/* This is Boss */
public static final class C0374a {
    /* renamed from: a */
    public final String f8550a;
    public C0374a(String str) {
        this.f8550a = str;
    }
...
}
/* This is Staff */
public static final class C0379c {
    /* renamed from: a */
    public final String f8556a;
    public C0379c(String str) {
        this.f8556a = str;
    }
...
}
/* This is getPerson(String, String) */
public final Object mo12141a(String str, String str2) {
    int hashCode = str.hashCode();
    if (hashCode != 3029869) {
        if (hashCode == 109757152 && str.equals("staff")) {
            return new C0379c(str2);
        }
    } else if (str.equals("boss")) {
        return new C0374a(str2);
    }
    return null;
}
/* This is main() */
public void mo12147a(boolean z) {
    Object a = mo12141a("Boss", "Peter");
    if (a != null) {
        System.out.print((C0374a) a);
        return;
    }
    throw new C3147k("null cannot be cast to non-null type Boss");
}

Highlighted points:

1. In the obfuscated code, Boss is still visible

How to prevent null checkings in generated code ?

Solution A:

fun main() {
    val temp = getPerson("boss", "Peter")
    if (temp != null) {
        val boss = temp as Boss
        print(boss)
    }
}

Solution B:

fun main() {
    val boss = getPerson("boss", "Peter") as? Boss
    print(boss?.name ?: "no boss")
}

Use case 2:

Slighly different from use case1:

open class A {
    open fun print() {

    }
}

class A1 : A() {
    override fun print() {
        print("A1")
    }
}

class A2 : A() {
    override fun print() {
        print("B1")
    }
}
/**
 * This function won't return null
 */
fun getA(isA1: Boolean): Any {
    return if (isA1) {
        A1()
    } else {
        A2()
    }
}

Look at the code below:

Non-obfuscated:
(getA(true) as A1).print()
Obfuscated:
Object c = mo12151c(true);
if (c != null) {
    ((C0374a) c).mo12159a();
}
// A1 is explored !!
throw new C3207k("null cannot be cast to non-null type A1");

Using same way to pretend:

val a1 = getA(true)
if (a1 != null) (a1 as A1).print()

Used in:

Hong Alarm - Apps on Google Play