#12921: initTc: unsolved constraints -------------------------------------+------------------------------------- Reporter: jlp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While working on a small project of mine, GHC panicked with the following error: {{{ lua-types-0.1.0.0: build Preprocessing executable 'lua-types' for lua-types-0.1.0.0... [2 of 3] Compiling Lua.Parser ( src/Lua/Parser.hs, .stack- work/dist/x86_64-osx/Cabal-1.24.1.0/build/lua-types/lua-types- tmp/Lua/Parser.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1.20161117 for x86_64-apple-darwin): initTc: unsolved constraints WC {wc_insol = [W] explist_a3nf :: t_a3ne[tau:1] (CHoleCan: explist) [W] funccall_a4dv :: t_a4du[tau:1] (CHoleCan: funccall)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} From a quick google search, it seems like this is a bug in the type checker. I'm not willing nor able to dive any further into the GHC code myself, though. I'll attach the code as it is, before looking for a workaround. I'm using stack, GHC version 8.0.1.20161117 for x86_64-apple-darwin. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12921 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler