Hi. Does anyone know how to cast generic type? I'm...

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[Yuku Kotani]

Hi. Does anyone know how to cast generic type? I'm trying to make mapOf() returns EnumMap if K is Enum.
An error occurs from this code.

@kotlin.internal.InlineOnly
public inline fun <reified K: Any, V> mapOf(): Map<K, V> =
    if (K::class.java.isEnum) EnumMap<K, V>(K::class.java)
    else emptyMap()

Type argument is not within its bounds.
Expected: Enum<K!>!
Found: K

[karelpeeters]

I think you'll have to cast it yourself

[karelpeeters]

K::class.java as Class<Enum<K>>

[Yuku Kotani]

Thanks for replying. The error occurs on here:
EnumMap<*K*, V>

[Yuku Kotani]

This code is impossible because the variable (K::class.java) must be a class of first type variable (K)
EnumMap<K, V>(K::class.java as Class<Enum<K>>)

[Yuku Kotani]

@karelpeeters Forgot to mention

[karelpeeters]

No there are notifications for everyone in a thread, I'm just thinking 🙂

[karelpeeters]

Hmm actually I can't find a way to write it out either...

[Yuku Kotani]

Oh sorry, Thank you for your help!

[karelpeeters]

It's frustrating though 😕

[karelpeeters]

Maybe ask on stackexchange?

[Yuku Kotani]

Good idea. Done.
https://stackoverflow.com/questions/49796845/casting-generic-type-on-kotlin

[karelpeeters]

You've got my upvote 🙂

[karelpeeters]

I'd say remove the inlineonly part, that's not really relevant.

[Yuku Kotani]

Thanks. Hmm, but this code works without any error:

@kotlin.internal.InlineOnly
public inline fun <reified K: Enum<*>, V> mapOf(): Map<K, V> =
    if (K::class.java.isEnum) EnumMap<K, V>(K::class.java)
    else emptyMap()

[karelpeeters]

But that doesn't do anything interesting, right?

[karelpeeters]

The bound on K for EnumMap<K, V> is now satisfied.

[Yuku Kotani]

Yes, this method receive non-enum objects as arguments.
An answerer might think i want to receive only enum objects.