Re: [GHC] #15549: Core Lint error with EmptyCase

#15549: Core Lint error with EmptyCase -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: merge Priority: normal | Milestone: 8.8.1 Component: Compiler (Type | Version: 8.4.3 checker) | Keywords: TypeFamilies, Resolution: | TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Compile-time | Test Case: crash or panic | typecheck/should_compile/T15549[ab] Blocked By: | Blocking: Related Tickets: #14729 | Differential Rev(s): Wiki Page: | https://gitlab.haskell.org/ghc/ghc/merge_requests/208 -------------------------------------+------------------------------------- Comment (by Marge Bot ): In [changeset:"2b90356d26b4699227816ad9424e766eccdb6c36/ghc" 2b90356d/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="2b90356d26b4699227816ad9424e766eccdb6c36" Fix #14729 by making the normaliser homogeneous This ports the fix to #12919 to the normaliser. (#12919 was about the flattener.) Because the fix is involved, this is done by moving the critical piece of code to Coercion, and then calling this from both the flattener and the normaliser. The key bit is: simplifying type families in a type is always a *homogeneous* operation. See #12919 for a discussion of why this is the Right Way to simplify type families. Also fixes #15549. test case: dependent/should_compile/T14729{,kind} typecheck/should_compile/T15549[ab] }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15549#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler