stagePlanner.go
func elideLiterals(root *evaluationStage) *evaluationStage {

	if root.leftStage != nil {
		root.leftStage = elideLiterals(root.leftStage)
	}

	if root.rightStage != nil {
		root.rightStage = elideLiterals(root.rightStage)
	}

	return elideStage(root)
}
func elideLiterals(root *evaluationStage) *evaluationStage {

	if root.leftStage != nil {
		root.leftStage = elideLiterals(root.leftStage)
	}

	if root.rightStage != nil {
		root.rightStage = elideLiterals(root.rightStage)
	}

	return elideStage(root)
}
/*
	Recurses through all operators in the entire tree, eliding operators where both sides are literals.
*/