I get an "ERROR Overload resolution ambiguity" for `(1..10).sumOf { if (it % 2 == 0) 1 else 0 }`. Th...

# getting-started

[nkiesel]

I get an "ERROR Overload resolution ambiguity" for (1..10).sumOf { if (it % 2 == 0) 1 else 0 }. This looks like a bug to me (I tried both 1.5.21 and 1.5.30). I can avoid that using e.g. (1..10).sumOf { if (it % 2 == 0) 1L else 0L } or (1..10).sumOf { if (it % 2 == 0) 1.toInt() else 0.toInt() }, but the first one produces a Long instead of an Int and the 2nd one is just ugly.

[ephemient]

https://youtrack.jetbrains.com/issue/KT-46360

[ephemient]

in the meanwhile, if you can supply the type through context, e.g.

val sum: Int = sumOf { ... }

that will work

[nkiesel]

thanks for the YouTrack link. However, val sum: Int = (1..10).sumOf { if (it % 2 == 0) 1 else 0 } still fails with the same error.
My personal belief is that the decision to support automatic promotions from Int literals to Long is a design mistake in Kotlin. Kotlin normally (and rightfully so) requires explicit conversions in all other places. So why then should I be allowed to use val l: Long = 1 and not be forced to use val l: Long = 1L?

[ephemient]

it's not an automatic promotion, it's that integer literals are a special subtype of all built-in integer types that they would fit in. https://kotlinlang.org/spec/type-system.html#subtyping-for-integer-literal-types