#9450: GHC instantiates Data instances before checking hs-boot files -------------------------------------+------------------------------------- Reporter: alanz | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.8.3 checker) | Keywords: deriving, hs- Resolution: | boot Operating System: Unknown/Multiple | Architecture: x86_64 Type of failure: Compile-time | (amd64) crash | Test Case: Blocked By: | Blocking: Related Tickets: #13591 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * related: => #13591 Comment: Interestingly, if you compile this with GHC 8.0.1 or later, you get an error described in #13591: {{{ $ /opt/ghc/8.0.1/bin/ghci HsLit.hs GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 4] Compiling HsLit[boot] ( HsLit.hs-boot, interpreted ) [2 of 4] Compiling HsExpr[boot] ( HsExpr.hs-boot, interpreted ) [3 of 4] Compiling HsExpr ( HsExpr.hs, interpreted ) HsExpr.hs:1:1: error: instance (Data.Data.Data id, Data.Data.Data (HsLit.TypeAnnot id), Data.Data.Data (HsLit.NameAnnot id)) => Data.Data.Data (HsExpr id) -- Defined at HsExpr.hs-boot:19:10 is defined in the hs-boot file, but not in the module itself HsExpr.hs-boot:17:1: error: Type constructor ‘HsExpr’ has conflicting definitions in the module and its hs-boot file Main module: data HsExpr i = E i | E2 i Boot file: type role HsExpr nominal abstract HsExpr i The roles do not match. Roles on abstract types default to ‘representational’ in boot files. *** Exception: expectJust showModule CallStack (from HasCallStack): error, called at compiler/utils/Maybes.hs:48:27 in ghc:Maybes }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9450#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler