# Split `self` creating a new sub-block having `line` has `last_line`.
	fun split(line: MDLine): MDBlock do
		# location for new block
		var new_loc = new MDLocation(
			first_line.as(not null).location.line_start,
			first_line.as(not null).location.column_start,
			line.location.line_end,
			line.location.column_end)
		# create block
		var block = new MDBlock(new_loc)
		block.first_line = first_line
		block.last_line = line
		first_line = line.next
		line.next = null
		if first_line == null then
			last_line = null
		else
			first_line.as(not null).prev = null
			# update current block loc
			location.line_start = first_line.as(not null).location.line_start
			location.column_start = first_line.as(not null).location.column_start
		end
		if first_block == null then
			first_block = block
			last_block = block
		else
			last_block.as(not null).next = block
			last_block = block
		end
		return block
	end