#14547: Wrong warning by -Wincomplete-patterns -------------------------------------+------------------------------------- Reporter: YoshikuniJujo | Owner: (none) Type: bug | Status: patch Priority: low | Milestone: Component: Compiler | Version: 8.2.1 Resolution: | Keywords: incomplete- | patterns OverloadedLists, | PatternMatchWarnings TypeFamilies Operating System: Linux | Architecture: x86 Type of failure: Incorrect | Test Case: error/warning at compile-time | deSugar/should_compile/T14547 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4624 Wiki Page: | -------------------------------------+------------------------------------- Changes (by dfeuer): * cc: dfeuer (added) Comment: In Simon's example, {{{#!hs f (toList -> []) = e1 f (toList -> (a:as)) = e2 }}} I don't see how it's at all relevant that `toList` is from an `IsList` instance. I imagine we ''always'' want to common up view patterns using the same function for coverage checking. For example, given {{{#!hs f (g -> P1) = e1 f P2 = e2 f (g -> P3) = e3 }}} I imagine we want to transform that to something like {{{#!hs f x | P1 <- gx = e1 | P2 <- x = e2 | P3 <- gx = e3 where gx = g x }}} when performing coverage checks. I don't know how the details work out for the pattern checker. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14547#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler