Re: [GHC] #14934: Repeated "impossible" go_axiom_rule error.

#14934: Repeated "impossible" go_axiom_rule error. -------------------------------------+------------------------------------- Reporter: galen | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.4.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: Compile-time | (amd64) crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4508 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"c3aea39678398fdf88166f30f0d01225a1874a32/ghc" c3aea39/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="c3aea39678398fdf88166f30f0d01225a1874a32" Fix #14934 by including axSub0R in typeNatCoAxiomRules For some reason, `axSub0R` was left out of `typeNatCoAxiomRules` in `TcTypeNats`, which led to disaster when trying to look up `Sub0R` from an interface file, as demonstrated in #14934. The fix is simple—just add `axSub0R` to that list. To help prevent an issue like this happening in the future, I added a `Note [Adding built-in type families]` to `TcTypeNats`, which contains a walkthrough of all the definitions in `TcTypeNats` you need to update when adding a new built-in type family. Test Plan: make test TEST=T14934 Reviewers: bgamari, simonpj Reviewed By: simonpj Subscribers: simonpj, rwbarton, thomie, carter GHC Trac Issues: #14934 Differential Revision: https://phabricator.haskell.org/D4508 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14934#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler