#13292: panic! (the 'impossible' happened): corePrepPgm --------------------------------------+--------------------------------- Reporter: jeiea | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- It doesn't seem like a serious problem, but I report it anyway. With stack's project template, I just removed `main` and `someFunc`'s type signature and changed `someFunc`'s definition to `return ()`. `stack build` worked well, but `stack repl` emitted this error message. {{{ D:\ghc-corePrepPgm\app\Main.hs:6:1: warning: [-Wdeferred-type-errors] • Couldn't match type ‘ghc-prim-0.5.0.0:GHC.Prim.Any’ with ‘IO’ Expected type: IO () Actual type: ghc-prim-0.5.0.0:GHC.Prim.Any () • In the expression: main When checking the type of the IO action ‘main’ ghc.EXE: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): corePrepPgm [False] cobox_r1bo = typeError @ 'VoidRep @ (Any :: (* -> *)) ~# (IO :: (* -> *)) "D:\\ghc-corePrepPgm\\app\\Main.hs:6:1: error:\n\ \ \\226\\128\\162 Couldn't match type \\226\\128\\152ghc-prim-0.5.0.0:GHC.Prim.Any\\226\\128\\153 with \\226\\128\\152IO\\226\\128\\153\n\ \ Expected type: IO ()\n\ \ Actual type: ghc- prim-0.5.0.0:GHC.Prim.Any ()\n\ \ \\226\\128\\162 In the expression: main\n\ \ When checking the type of the IO action \\226\\128\\152main\\226\\128\\153\n\ \(deferred type error)"# Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13292 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler