Re: [GHC] #13154: Standalone-derived anyclass instances aren't as permissive as empty instances

#13154: Standalone-derived anyclass instances aren't as permissive as empty instances -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: RyanGlScott Type: bug | Status: patch Priority: normal | Milestone: 8.6.1 Component: Compiler (Type | Version: 8.1 checker) | Resolution: | Keywords: deriving Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4337, Wiki Page: | Phab:D4370 -------------------------------------+------------------------------------- Comment (by Ryan Scott ): In [changeset:"f4336593a390e6317ac2852d8defb54bfa633d3e/ghc" f4336593/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="f4336593a390e6317ac2852d8defb54bfa633d3e" Slight refactor of stock deriving internals Summary: Before, the `hasStockDeriving` function, which determines how derived bindings should be generated for stock classes, was awkwardly separated from the `checkSideConditions` function, which checks invariants of the same classes that `hasStockDeriving` does. As a result, there was a fair deal of hoopla needed to actually use `hasStockDeriving`. But this hoopla really isn't required—we should be using `hasStockDeriving` from within `checkSideConditions`, since they're looking up information about the same classes! By doing this, we can eliminate some kludgy code in the form of `mk_eqn_stock'`, which had an unreachable `pprPanic` that was stinking up the place. Reviewers: bgamari, dfeuer Reviewed By: bgamari Subscribers: dfeuer, rwbarton, thomie, carter GHC Trac Issues: #13154 Differential Revision: https://phabricator.haskell.org/D4370 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13154#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler