#12549: Panic on ":t datatypeName" --------------------------------------+--------------------------------- Reporter: johnleo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- Reproduction: {{{#!hs GHCi, version 8.1.20160826: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /Users/leo/.ghci Prelude> :m + GHC.Generics :m + GHC.Generics Prelude GHC.Generics> :t datatypeName :t datatypeName ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.1.20160826 for x86_64-apple-darwin): ASSERT failed! CallStack (from HasCallStack): assertPprPanic, called at compiler/types/TyCoRep.hs:2094:44 in ghc:TyCoRep checkValidSubst, called at compiler/types/TyCoRep.hs:2122:17 in ghc:TyCoRep substTy, called at compiler/typecheck/TcMType.hs:793:24 in ghc:TcMType in_scope InScope {k1_a1X8} tenv [a1X0 :-> k1_a1X8[tau:3]] cenv [] tys [k_a1X4[tau:3] → (k1_a1X0 → *) → k1_a1X0 → ★] cos [] needInScope [a1X4 :-> k_a1X4[tau:3]] Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12549 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler