hello, anyone has fail compile issue with the new ...

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[hoang]

hello, anyone has fail compile issue with the new kotlin 1.4.20 and Optional<V>

Type mismatch: inferred type is Optional<V!!> but Optional<V> was expected

the same code compile ok in kotlin 1.4.10

fun first(vPredicate: (V) -> Boolean): Optional<V> {
        val v: V? = firstOrNull(vPredicate)
        return if (v == null) {
            Optional.empty()
        } else {
            Optional.of(v)
        }
    }

the errored line is the one that return Optional.empty()

[Victor Petukhov]

Could you provide self-contained example?
Here there is no declaration of V and firstOrNull.
I couldn’t reproduce it with the following example:

import java.util.*

fun <V> first(vPredicate: (V) -> Boolean): Optional<V> {
    val v: V? = null
    return if (v == null) {
        Optional.empty()
    } else {
        Optional.of(v)
    }
}

[hoang]

This is the self-contained code:

import java.util.*
import java.util.concurrent.ConcurrentHashMap

abstract class BaseCache2<K, V> {

    private val cache = ConcurrentHashMap<K, V>()

    fun firstOrNull(vPredicate: (V) -> Boolean): V? = cache.values.firstOrNull(vPredicate)

    fun first(vPredicate: (V) -> Boolean): Optional<V> {
        val v: V? = firstOrNull(vPredicate)
        return if (v == null) {
            Optional.empty()
        } else {
            Optional.of(v)
        }
    }
}

[hoang]

well, even just return Optional.empty() in place of generics Optional<V> is enough to cause compile error:

abstract class GenericsOverV<V> {
    fun justEmpty(): Optional<V> {
        return Optional.empty()
    }
}