Scala中的递归数据类型

Question

Hi I was wondering if someone could explain this signature I found in the Spark codebase. It looks like a recursive datatype, it's used to build the query plan so it kind of makes sense. Does anyone have anymore detailed knowledge of this?

abstract class TreeNode[BaseType <: TreeNode[BaseType]] extends Product 

Answer 1

It is F-Bounded Types (or self-recursive types ). Not scala specific, eg equivalent in java

public abstract class Enum<E extends Enum<E>> implements Comparable<E>

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