Re: [GHC] #11396: deriving Ix with custom ifThenElse causes "Bad call to tagToEnum#"

#11396: deriving Ix with custom ifThenElse causes "Bad call to tagToEnum#" -------------------------------------+------------------------------------- Reporter: Lemming | Owner: bgamari Type: bug | Status: patch Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.0.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1797 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"5cce09543db827e662539523ffff4513deb92777/ghc" 5cce0954/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="5cce09543db827e662539523ffff4513deb92777" Use (&&) instead of `if` in Ix derivation We were previously using `if` in the derivation of `Ix` instances. This interacts badly with RebindableSyntax as the typechecker doesn't infer the type of the argument we give to `tagToEnum#`. Previously we produced, `if (ch >= ah) then (ch <= bh) else False`. We now produce `(ch >= ah) && (ch <= bh)` Fixes #11396. Test Plan: Validate Reviewers: austin, simonpj Reviewed By: simonpj Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1797 GHC Trac Issues: #11396 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11396#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler