# File lib/rake.rb, line 1702
1702:     def [](task_name, scopes=nil)
1703:       task_name = task_name.to_s
1704:       self.lookup(task_name, scopes) or
1705:         enhance_with_matching_rule(task_name) or
1706:         synthesize_file_task(task_name) or
1707:         fail "Don't know how to build task '#{task_name}'"
1708:     end