#13021: Inaccessible RHS warning is confusing for users -------------------------------------+------------------------------------- Reporter: mpickering | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton): My confusion here is at a very basic level. `_` is a pattern such that any set of pattern matches which includes `_` is total. Yet in a function like {{{ f :: Maybe a -> Int f Nothing = 0 f _ = 1 }}} the first equation is not redundant in a practical sense, even though the pattern match would still be total without it. There's more to life than totality of pattern matches. I thought that a `{-# COMPLETE p1, ..., pn #-}` pragma was just supposed to mean that a function that matches all of the `pi` should be regarded as total. It doesn't make any sense to me for the compiler to use this knowledge plus the definitions of the `pi` to make any conclusions about whether other values are possible or not. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13021#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler