# File lib/rake.rb, line 1724
1724:     def [](task_name, scopes=nil)
1725:       task_name = task_name.to_s
1726:       self.lookup(task_name, scopes) or
1727:         enhance_with_matching_rule(task_name) or
1728:         synthesize_file_task(task_name) or
1729:         fail "Don't know how to build task '#{task_name}'"
1730:     end