Why doesn’t this work ```@OptIn(ExperimentalContra...

# random

[iamthevoid]

Why doesn’t this work

@OptIn(ExperimentalContracts::class)
private fun <T : Any> T?.isNotNull(): Boolean {
    contract {
        returns(true) implies (this@isNotNull != null)
    }
    return this != null
}

[Dominaezzz]

I don't think contracts are preserved with variables like that.

[Dominaezzz]

Does it work when you do != null ?

[iamthevoid]

paymentRule ?: return

works

check(paymentRule != null)

works

After all of they payment rule is not null in scope

[iamthevoid]

But i want reach something different

[iamthevoid]

i want boolean, that means, that value is null

[Dominaezzz]

The first two are easy for the compiler.

[Dominaezzz]

The compiler can't do that with the boolean you're trying to use.,

[Dominaezzz]

s/can't/doesn't/

[iamthevoid]

That is purpose of contracts, is not it?

[Dominaezzz]

I suppose so but contracts are not in their final form yet.

[Klitos Kyriacou]

Isn't this exactly the same reason foo compiles but bar doesn't? Or are contracts meant to do something a bit more magical that that?

fun foo(n: Int?) {
    if (n != null) {
        val m: Int = n
    }
}

fun bar(n: Int?) {
    val b = n != null
    if (b) {
        val m: Int = n
    }
}

[Dominaezzz]

Exactly! That's what I'm trying to say. The compiler drops the contract once the variable b is used.