#9628: Add Annotations to the AST to simplify source to source conversions -------------------------------------+------------------------------------- Reporter: alanz | Owner: alanz Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.9 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: D297 | -------------------------------------+------------------------------------- Comment (by NeilMitchell): Alan and I debated this point, and I was the one who suggested the many data types approach (although I wouldn't go as far as saying I advocate it - I'm somewhat neutral). My concern was that if you do the dynamic approach you have to document each one of those strings, and the documentation has to be correct or the users won't have a clue what is going on, and if you update it all your clients will break and no one will realise. The documentation will basically be as long as the data types, but won't be statically checked on either side, and will very likely end up being wrong. Maybe a hybrid approach is to have location information for keywords like "of", "case", "where", "(" and ")". You can have a fixed static enumeration of keywords, so you have type safety, and every keyword is optionally in every AST. The number of keywords is relatively small, and which keyword is contained within each AST node doesn't require documenting (the lexical structure makes it pretty obvious). You end up with no requirement for fragile docs, one data type with a fairly small number of entries, and reasonable safety for both the producer and consumer. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9628#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler