AstNodeLinks
class AstNodeLinks(var parent: AstNode? = null, var firstChild: AstNode? = null, var lastChild: AstNode? = null, var previous: AstNode? = null, var next: AstNode? = null)
All the pointers that can exist for a node in an AST.
Links are mutable to make it possible to instantiate a Node which can then reconfigure its children and siblings. Please do not modify the links after an ASTNode is created and the scope is finished.