```val buffer = ByteBuffer.allocate(4450)``` intellij says the inferred type of this is `val buffer:...

# getting-started

[LastExceed]

val buffer = ByteBuffer.allocate(4450)

intellij says the inferred type of this is val buffer: (ByteBuffer..ByteBuffer?) what does that mean? this isn't even valid code when i try to type this out myself. the code compiles fine on my machine, but jitpack.io fails because of a type mismatch. what is going on here?

[Michael de Kaste]

ByteBuffer allocation is probably Java Interrop, which is either nullable or not. You'll probably have to handle something like:
val buffer = ByteBuffer.allocate(4450)!!
or
val buffer = ByteBuffer.allocate(4450) ?: return someFailedReturn

[Michael de Kaste]

can't the type just be ByteBuffer?

[LastExceed]

shouldnt it be ByteBuffer! then ?

[LastExceed]

i updated to kotlin 1.6.20 which just released, and now it does show ByteBuffer! as expected. however jitpack still fails with Type mismatch: inferred type is Buffer! but ByteBuffer was expected

[LastExceed]

i am so confused

[Sam]

Inferred type is Buffer? That sounds like something from a different library entirely. Is that a typo or is that the exact wording of the error message?

[LastExceed]

its copypasted from the log. i was wondering about this too

[Sam]

Are you using any other libraries like ktor or okio?

[LastExceed]

i am using ktor, but i already double checked that i'm not using the wrong type. its definitely java.nio.ByteBuffer everywhere

[ephemient]

you are probably running into a Java version difference somewhere

[ephemient]

e.g. ByteBuffer.clear() is a method of its Buffer supertype on Java 8- and so returns a Buffer, while there is a specific overload on Java 9+ that returns a ByteBuffer instead

[ephemient]

it's a pain, but unrelated to Kotlin and whatever you're seeing in your IDE

[dmitriy.novozhilov]

T! is a short form of (T..T?) type

[LastExceed]

@ephemient ah yes that seems to be it. thanks!

@dmitriy.novozhilov thats good to know, can you elaboraote or point me to a resource where i can learn more about this?

[ephemient]

it's internal notation for lower and upper bounds, it's not something you can type yourself (well, not that you can type the platform type yourself either)

[dmitriy.novozhilov]

@LastExceed
Kotlin documentation: https://kotlinlang.org/docs/java-interop.html#null-safety-and-platform-types
Kotlin specification: https://kotlinlang.org/spec/type-system.html#flexible-types

[LastExceed]

thanks

[ephemient]

https://youtrack.jetbrains.com/issue/KTOR-1398 btw. there's supposed to be a -Xjdk-release coming in Kotlin 1.7, similar to Java's --release flag, to make it a bit less painful to target older JDKs when building with a newer one'