Not sure where to ask this :sweat_smile: Regarding Contracts, I was wondering if it’s possible (or w...

# random

[pablisco]

Not sure where to ask this 😅
Regarding Contracts, I was wondering if it’s possible (or will ever be) to signal something about a parameter if a lambda is called.
Like this:

[pablisco]

This would mean that, if the block is run, then the subject is not null (or other condition)

[louiscad]

I think stuff?.let { } does the same thing as what you want, do you have another use case?

[pablisco]

Yeah that one does, however this case is a replacement for:

receiver.run { stuff?.let { this.doSomethingAndReturnSameTypeAsReceiver(stuff) } ?: receiver }

[pablisco]

Another use case if we could do:

calls(block) implies (subject is AppCompatActivity)

Then we could define something like:

fun Activity.ifAppCompat(block: () -> R): R {
  contract {
    calls(block) implies (this is AppCompatActivity)
  }
  if(this is AppCompatActivity) {
    block()
  }
}

That said, these could potentially be inferred by the compiler. But making it explicit will probably be more efficient
(say someone that knows close to nothing about the Kotlin compiler 😅 )

[louiscad]

That AppCompat example is less abstract, but can't you simply add an AppCompatActivity receiver for the block lambda?