Re: [GHC] #10011: The Data instance for Ratio violates internal invariants.

#10011: The Data instance for Ratio violates internal invariants. -------------------------------------+------------------------------------- Reporter: ekmett | Owner: ekmett Type: bug | Status: patch Priority: normal | Milestone: 7.10.1 Component: Core Libraries | Version: 7.10.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: Phab:D625 -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel ): In [changeset:"79b0d0e633af8302d2dd907663a4a231cd889b67/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="79b0d0e633af8302d2dd907663a4a231cd889b67" Restore invariant in `Data (Ratio a)` instance The Data instance for `Ratio` just uses the raw `:%` constructor and doesn't check that the result is reduced to normal form. The fix is to add back the `Integral` constraint on the Data instance (which was dropped in c409b6f30373535) and to use `%` rather than `:%` in the `gfoldl` and `gunfold` implementation. This restores the invariant and matches the behavior of "virtual constructors" we've used to patch up such problems elsewhere. This addresses #10011 Reviewed By: ekmett, austin Differential Revision: https://phabricator.haskell.org/D625 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10011#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler