Reference to the last parent in the Ordered Tree

Is used to handle the initial node parent and workaround possible inconsistent ANode::parent

Property definitions

nitc $ ASTDump :: last_parent
	# Reference to the last parent in the Ordered Tree
	# Is used to handle the initial node parent and workaround possible inconsistent `ANode::parent`
	private var last_parent: nullable ANode = null
src/parser/parser_nodes.nit:190,2--192,47