#8305: ghci macros override built-ins for command expansion -------------------------------------+------------------------------------ Reporter: rwbarton | Owner: Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: GHCi | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: #8113 -------------------------------------+------------------------------------ Comment (by rwbarton): With the caveat that if we "expand to built-in" and there is a macro of the same name, we use the macro instead. But this makes it all sound more confusing than it really is. I imagine two stages in the interpretation of a ghci command: first name completion (`String -> String`), then name resolution (`String -> Maybe (Either UserMacro BuiltinCommand)`). I want the name completion to work exactly as in every previous released version of ghci: `:t` always means the same thing as `:type` unless the user has a macro named specifically `:t`. This is important so that anyone who's not using the new ability to override built-ins has an unchanged ghci experience. The name resolution step now prefers macros over built-ins, to allow the user (or a tool like cabal sandboxes) to override the meaning of built-in commands. The #8113 patch implements the desired new name resolution behavior, but it changes the name completion behavior at the same time. Here are some example scenarios. 1. User has a macro `:time`, and enters `:t 3`. * ''ghci 7.6 behavior'' `:type 3` * ''current HEAD behavior'' `:time 3` * ''my desired behavior'' `:type 3`, like ghci 7.6 2. User has a macro `:type`, and enters `:t 3`. * ''ghci 7.6 behavior'' `:type 3`, with the built-in `:type` (built-ins can't be overridden in 7.6) * ''current HEAD behavior'' `:type 3`, with the user's `:type` macro * ''my desired behavior'' `:type 3`, with the user's `:type` macro, like current HEAD 2. User has a macro `:time` and also a macro `:type`, and enters `:t 3`. * ''ghci 7.6 behavior'' `:type 3`, with the built-in `:type` * ''current HEAD behavior'' `:time 3` * ''my desired behavior'' `:type 3`, with the user's `:type` macro; different from both 7.6 and HEAD -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8305#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler