#8888: Document Coercible in user's guide -------------------------------------+------------------------------------ Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.8.1 Component: Documentation | Version: 7.8.1-rc2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonpj): Well, there really is a new form of constraint, written `(Coercible s t)`. It isn't really a class constraint, although by design it behaves in analogous ways. But you can't declare instances of `Coercible`, and it has special constraint-solving rules all of its own. That sounds like a language extension to me! There is no new syntax, but there ''is'' a new sort of constraint. I think it deserves its own section in Chapter 7. That's where users will lok. As to "spreading the documentation around", where (apart from the paper) are the solving rules for `Coercible` given? Perhaps with the (data type!) `Corecible` in `GHC.Types`? I'd be happier with a reference from there to the user manual, I think. Mind you, I'm puzzled. `Data.Coerce` in package `base` imports `Coercible` from `GHC.Prim` (which has no corresponding Haskell module). But `GHC.Types` in package `ghc-prim` defines `Coercible` (as a data type). So where is it defined? In `GHC.Prim` or `GHC.Types`? The Name defined in `PrelNames` suggests the latter. Also oddly, `PrelNames` defines `gHC_COERCIBLE` which seems to be unused ... delete? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8888#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler