Is the production a part of a single line (without being a block)

Computed by parentize_tokens

Property definitions

nitc :: astutil $ Prod :: is_span
	# Is the production a part of a single line (without being a block)
	# Computed by `parentize_tokens`
	fun is_span: Bool
	do
		if first_token == null or last_token == null then return false
		return not is_block and location.line_start == location.line_end
	end
src/astutil.nit:55,2--61,4