Hey guys is there a way to tell the compiler to not accept g

Question

Hey guys is there a way to tell the compiler to not accept generic types as reified type argument ``` inline fun lt reified Value Any gt test1 Value = TODO inline fun lt reified Value Any gt test2 List lt Value gt = TODO val test List lt Int gt = test1 ``` In the example using `test1 ` accidentally instead of `test2 ` should raise an error because I cannot get the generic type of the `List` anyway

Ruckus · Answer

But reified types are generic

Max Russek · Answer

I believe that this would require higher kinded types which Kotlin doesn t support

raulraja · Answer

In your example your applied generic is `List lt Int gt ` not `List` in higher kind position

Marc Knaup · Answer

< raulraja> I guess that doesn t allow me to make `test1 ` behave differently for `List lt gt ` does it

Marc Knaup · Answer

< Ruckus> i e `Value = Int` `Int` isn t generic is it Or am I using the wrong term somewhere

Max Russek · Answer

In a type system without higher kinded types there is no way to specify for a generic parameter that it is a base type i e kind ` ` or a generic type i e kind ` gt ` You have to take all of them both kinds ` ` and ` gt `

Ruckus · Answer

Okay I think I now see what you mean I meant that `Value` in your example is a generic type which is required by `reified` If you re saying you don t want `Value` to resolve to a type which in turn has a generic type no it s not possible as far as I am aware If you re saying you want different behavior if there is a generic parameter you can use reflection

Marc Knaup · Answer

Okay thanks you guys +1 Will work around it for now by using clear distinct names and hope that people won t use the wrong one

raulraja · Answer

I m not sure what you are trying to achieve but it s easy to see what the result would be if you type your function ``` test1 lt List lt Int gt gt Value is `List lt Int gt ` test2 lt Int gt List lt Int gt ``` But yeah you can t use a kind in that position because of no HKTs yet <https github com Kotlin KEEP pull 87> wink

raulraja · Answer

If that makes it to the lang you d be able to use kinds in that position ``` fun lt F lt gt A B gt transform fa F lt A gt f A gt B F lt B gt given Functor lt F gt = F map fa f ``` The you can use your polymorphic function to satisfy all types for a which a Functor instance exists ``` transform listOf 1 it + 1 transform Option 1 it + 1 transform Try 1 it + 1 ```

Marc Knaup · Answer

looks complicated open mouth but thanks

damian · Answer

There is an annotation called `PureReifiable` to denote that a particular reified type parameter can be a generic type <https github com JetBrains kotlin blob master core builtins src kotlin internal InternalAnnotations kt L25> but it is `internal` confused

raulraja · Answer

< damian> do you know of any examples that use ` PureReifiable`

damian · Answer

< raulraja> Looks like it s only used for things like `arrayOf` `emptyArray` `arrayOfNulls`