#13965: COMPLETE sets nerf redundant pattern-match warnings -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Resolution: | Keywords: | PatternSynonyms, | 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 RyanGlScott): I think this comparison is somewhat unfair. For one thing, this isn't even a situation where the `COMPLETE` set would kick in, since GHC would pick the original set of constructors over the `COMPLETE` set. Removing the "redundant" match on `B` wouldn't introduce any warnings either, but that is correct behavior, since now GHC uses the `COMPLETE` set. The original program is of a different nature, since the only option it has is a `COMPLETE` set (as evidenced by `module Foo`). Moreover, removing the redundant match on `F` doesn't change the fact that GHC is using the same `COMPLETE` set. This is why I argue that GHC's warning behavior on the original program is mistaken, since the second match on `F` is truly redundant, even after factoring in the semantics of `COMPLETE` sets. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13965#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler