#10583: Chaos in Lexeme.hs -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I've been looking at the `Lexeme` module (in `basicTypes`), where -- as far as I can tell -- utter chaos reigns. (Full disclosure: I wrote this module some time ago, inheriting its code from various places. But I clearly did a poor job of it.) Here is a sampling of the chaos: * `isLexConSym` claims to recognize type and data constructor infix symbols. But it requires symbols to start with a `:` (or be `->`). This is out-of-date with respect to the change in type constructor infix symbols in 7.6(?), which now do not need to start with a `:`. * `isVarSymChar` and `okSymChar` both purport to recognize characters that are valid parts of symbolic identifiers. But they have entirely different, unrelated implementations. These should be the '''same''' function, I believe. * The `notFollowedBySymbol` function defined in `parser/Lexer.x` overlaps with the functions above. But it has a '''third''' implementation, different than either of these other two. * The `isLexXXX` functions all just look at first characters, except for `isLexVarSym`, which looks at all characters. There is a reason for this -- that GHC-generated names start with a `$` but should be printed prefix -- but I'm not sure I buy it. Is it sufficient to look at the first two characters instead of the first one? I'm happy to make the code changes around this, but I need some advice from someone who has more knowledge about both Haskell's lexical structure and quite possibly Unicode. Happily, the function in `Lexeme` are not used much. But it would be awfully nice if they did the right thing when they are used. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10583 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler