kotlin get "Type argument is not within its bounds" for recursive bounds

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Get recursive "Type argument is not within its bounds" for recursive bounds when initializing an object

class RawType {
  
  inner class BoundRecursively<T : BoundRecursively<T>?>

  fun test() {
    
    val boundRecursively = BoundRecursively<BoundRecursively<Any>?>()
  }
}

the compiler gives error


Type argument is not within its bounds: should be subtype of 'RawType.BoundRecursively<TypeVariable(T)>?'
Type argument is not within its bounds: should be subtype of 'RawType.BoundRecursively<Any>?'
Type argument is not within its bounds: should be subtype of 'Any'
Type argument is not within its bounds: should be subtype of 'RawType.BoundRecursively<RawType.BoundRecursively<Any>?>?'
Type argument is not within its bounds: should be subtype of 'RawType.BoundRecursively<RawType.BoundRecursively<Any>?>?'
Type argument is not within its bounds: should be subtype of 'RawType.BoundRecursively<Any>?'

Any suggestion on how to fix the initialization

kotlin generics
1 Answers

When you intialize an object:

val boundRecursively = BoundRecursively<BoundRecursively<Any>?>()

First of all intializing an object with itself is very dangerous. You should be careful when doing this. Second of all you need a stopping condition, otherwise BoundRecusively will intialize an infinite number of BoundRecursively objects. You need to tell it when to stop intializing BoundRecursively objects.

user_131909500
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