# Expect a `document` production.
	private fun expect_document: Bool do
		var got_doctype = false
		var got_element = false

		# If the document start with `<`, it may start with a XML declaration,
		# a processing instruction, a comment, a `DOCTYPE` declaration, the
		# root element or a white space.
		if lexer.accept('<') then
			if lexer.accept('?') then
				if not expect_pi_or_xml_decl then return false
			else if lexer.accept('!') then
				if lexer.accept('-') then
					if not lexer.expect('-',
								" at the beginning of a comment") or
								not expect_comment then
						return false
					end
				else
					if not expect_doctype_decl then return false
					got_doctype = true
				end
			else
				if not expect_root then return false
				# The `DOCTYPE` declaration *must* come before the root
				# element.
				got_doctype = true
				got_element = true
			end
		else if not lexer.accept_s then
			return lexer.fire_unexpected_char(
					". Expecting a white space or `<`")
		end

		# After the XML declaration (if there is one), the document may contain
		# processing instructions, comments, the `DOCTYPE` declaration and
		# the root element.
		# These productions may be separated by white space.
		while not got_element do
			if lexer.accept('<') then
				if lexer.accept('?') then
					if not expect_pi then return false
				else if lexer.accept('!') then
					if lexer.accept('-') then
						if not lexer.expect('-',
									" at the beginning of a comment") or
									not expect_comment then
							return false
						end
					else if got_doctype then
						return lexer.fire_unexpected_char(". Expecting `-`")
					else if expect_doctype_decl then
						got_doctype = true
					else
						return false
					end
				else
					if not expect_root then return false
					# The `DOCTYPE` declaration *must* come before the root
					# element.
					got_doctype = true
					got_element = true
				end
			else if not lexer.accept_s then
				return lexer.fire_unexpected_char(
						". Expecting a white space or `<`")
			end
		end
		return expect_miscs
	end