#12390: List rules for `Coercible` instances -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: tellah Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: ghci059 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D3634 Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Here are some design notes off the top of my head: I don't want to clutter `TyThing` with this, as it's unclear where within `TyThing` the documentation should go. In `TyCon`? Perhaps, but I don't love it. Instead, `InteractiveEval.getInfo` could return 5 things instead of 4; the fifth is an `SDoc` with extra text that should be printed. (It would normally be `empty`.) Naturally, you will have to add the fifth return value to `HscMain.hscTcRnGetInfo` and `TcRnDriver.tcRnGetInfo`. That last function can just call a new `lookupCustomDoc` function. That function can be defined in `PrelInfo`; it would refer to a `UniqFM SDoc` that associates `Unique`s with `SDoc`s. The `SDoc`s could (for now) just be hard-coded in `PrelInfo`. Certainly baked-in goodies other than `Coercible` can benefit from this new behavior. Perhaps it would be better to store the printed strings outside of a Haskell source file, but we don't have to over-design to begin with. Before implementing this, @tellah, perhaps someone else who is not a newcomer can opine on my design choices here. And, thanks! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12390#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler