# File lib/rake/task_manager.rb, line 44
44:     def [](task_name, scopes=nil)
45:       task_name = task_name.to_s
46:       self.lookup(task_name, scopes) or
47:         enhance_with_matching_rule(task_name) or
48:         synthesize_file_task(task_name) or
49:         fail "Don't know how to build task '#{task_name}'"
50:     end