What is expected behavior for loop below (what sho...

# general-advice

[PHondogo]

What is expected behavior for loop below (what should be printed)?

for (v in UByte.MIN_VALUE..UByte.MAX_VALUE) {
    println(v) // it is going after 255 and more. Why?
}

[ephemient]

val range = UByte.MIN_VALUE..UByte.MAX_VALUE
for (v in range) println(v)

seems to work, so it seems like a compiler bug with intrinsification

[ephemient]

for (v in UByte.MIN_VALUE.toUInt()..UByte.MAX_VALUE.toUInt()) {
    println(v)
}

also seems to work, despite being the same type of range

[ephemient]

for (v in UByte.MAX_VALUE..UByte.MAX_VALUE) println(v)
println(UInt.MAX_VALUE)

prints the same thing so there is some inappropriate sign extension happening

[ephemient]

file a YouTrack issue

[PHondogo]

Found 2 old issues with same problem. Added comment to them.
https://youtrack.jetbrains.com/issue/KT-32044/For-loop-over-full-UByte-range-terminates-at-UInt-bound.
https://youtrack.jetbrains.com/issue/KT-67383/Incorrect-optimisation-when-optimising-for-loop-with-UByte

[PHondogo]

May be it is some regression in K2

[ephemient]

no I think this is a backend bug. for (v in UByte.MAX_VALUE..UByte.MAX_VALUE) println(v) prints the same wrong thing since Kotlin 1.7

[Klitos Kyriacou]

And it's not just UByte. It's also a bug with UShort.

[ephemient]

that's not surprising, they both operator fun rangeTo(...): UIntRange