21:53:40aethhowever, they usually provide the functionality to look up the source (which e.g. Emacs uses) so you could, if it is valid (and not guaranteed to still be around, either), read the file
21:54:04aethI wouldn't be surprised if e.g. SLIME already supports this as an alternative to M-.
21:54:18aethbut if you need to rely on it, you have to have a macro that saves it.