Re: [GHC] #14813: EmptyCase thinks pattern match involving type family is not exhaustive, when it actually is

#14813: EmptyCase thinks pattern match involving type family is not exhaustive, when it actually is -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple error/warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D5094 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Krzysztof Gogolewski ): In [changeset:"e72d7880b940881d38b8c3db9a00d5d007b1458f/ghc" e72d788/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="e72d7880b940881d38b8c3db9a00d5d007b1458f" Normalise EmptyCase types using the constraint solver Summary: Certain `EmptyCase` expressions were mistakently producing warnings since their types did not have as many type families reduced as they could have. The most direct way to fix this is to normalise these types initially using the constraint solver to solve for any local equalities that may be in scope. Test Plan: make test TEST=T14813 Reviewers: simonpj, bgamari, goldfire Reviewed By: simonpj Subscribers: rwbarton, carter GHC Trac Issues: #14813 Differential Revision: https://phabricator.haskell.org/D5094 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14813#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler