#13838: -Wdeferred-type-errors; ghc: panic!; VoidRep; ((() -> ()) :: *) ~# (IO Any :: *) -------------------------------------+------------------------------------- Reporter: harry | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- My Compiler told me to report this so here you go: {{{ [1 of 1] Compiling Main ( ghc_bug.hs, interpreted ) ghc_bug.hs:3:1: warning: [-Wdeferred-type-errors] * Couldn't match expected type `IO t0' with actual type `() -> ()' * Probable cause: `main' is applied to too few arguments In the expression: main When checking the type of the IO action `main' ghc_bug.hs:3:8: warning: [-Wdeferred-type-errors] * Couldn't match expected type `() -> () -> ()' with actual type `()' * The function `()' is applied to one argument, but its type `()' has none In the expression: () () In an equation for `main': main = () () ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): corePrepPgm [False] cobox_r1a0 = typeError @ 'VoidRep @ ((() -> ()) :: *) ~# (IO Any :: *) "ghc_bug.hs:3:1: error:\n\ \ * Couldn't match expected type `IO t0' with actual type `() -> ()'\n\ \ * Probable cause: `main' is applied to too few arguments\n\ \ In the expression: main\n\ \ When checking the type of the IO action `main'\n\ \(deferred type error)"# Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} {{{#!hs main :: () -> () main = () () }}} which that in "ghc_bug.hs" "ghc ghc_bug.hs -fdefer-type-errors -dcore-lint -v" gives me the following: {{{ Glasgow Haskell Compiler, Version 8.0.1, stage 2 booted by GHC version 7.10.3 Using binary package database: /usr/lib/ghc-8.0.1/package.conf.d/package.cache Using binary package database: /home/harry/.ghc/x86_64-linux-8.0.1/package.conf.d/package.cache loading package database /usr/lib/ghc-8.0.1/package.conf.d loading package database /home/harry/.ghc/x86_64-linux-8.0.1/package.conf.d wired-in package ghc-prim mapped to ghc-prim-0.5.0.0 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1 wired-in package base mapped to base-4.9.0.0 wired-in package rts mapped to rts wired-in package template-haskell mapped to template-haskell-2.11.0.0 wired-in package ghc mapped to ghc-8.0.1 wired-in package dph-seq not found. wired-in package dph-par not found. Hsc static flags: loading package database /usr/lib/ghc-8.0.1/package.conf.d loading package database /home/harry/.ghc/x86_64-linux-8.0.1/package.conf.d wired-in package ghc-prim mapped to ghc-prim-0.5.0.0 wired-in package integer-gmp mapped to integer-gmp-1.0.0.1 wired-in package base mapped to base-4.9.0.0 wired-in package rts mapped to rts-1.0 wired-in package template-haskell mapped to template-haskell-2.11.0.0 wired-in package ghc mapped to ghc-8.0.1 wired-in package dph-seq not found. wired-in package dph-par not found. *** Chasing dependencies: Chasing modules from: *ghc_bug.hs !!! Chasing dependencies: finished in 0.42 milliseconds, allocated 0.211 megabytes Stable obj: [] Stable BCO: [] Ready for upsweep [NONREC ModSummary { ms_hs_date = ****-**-** **:**:**.********** *** ms_mod = Main, ms_textual_imps = [(Nothing, Prelude)] ms_srcimps = [] }] *** Deleting temp files: Deleting: compile: input file ghc_bug.hs *** Checking old interface for Main: [1 of 1] Compiling Main ( ghc_bug.hs, ghc_bug.o ) *** Parser [Main]: !!! Parser [Main]: finished in 0.14 milliseconds, allocated 0.089 megabytes *** Renamer/typechecker [Main]: !!! Renamer/typechecker [Main]: finished in 28.70 milliseconds, allocated 14.769 megabytes *** Desugar [Main]: Result size of Desugar (after optimization) = {terms: 19, types: 52, coercions: 4} *** Core Linted result of Desugar (after optimization): *** Core Lint errors : in result of Desugar (after optimization) *** <no location info>: warning: [RHS of cobox_aOD :: ((() -> ()) :: *) ~# (IO Any :: *)] The type of this binder is primitive: cobox_aOD Binder's type: ((() -> ()) :: *) ~# (IO Any :: *) *** Offending Program *** main :: () -> () [LclIdX, Str=DmdType] main = case typeError @ 'VoidRep @ (() :: *) ~# ((() -> () -> ()) :: *) "ghc_bug.hs:2:8: error:\n\ \ * Couldn't match expected type `() -> () -> ()'\n\ \ with actual type `()'\n\ \ * The function `()' is applied to one argument,\n\ \ but its type `()' has none\n\ \ In the expression: () ()\n\ \ In an equation for `main': main = () ()\n\ \(deferred type error)"# of cobox_aOE { __DEFAULT -> (() `cast` (Sub cobox_aOE :: (() :: *) ~R# ((() -> () -> ()) :: *))) () } $trModule :: Module [LclIdX, Str=DmdType] $trModule = Module (TrNameS "main"#) (TrNameS "Main"#) cobox_aOD :: ((() -> ()) :: *) ~# (IO Any :: *) [LclId[CoVarId], Str=DmdType] cobox_aOD = typeError @ 'VoidRep @ ((() -> ()) :: *) ~# (IO Any :: *) "ghc_bug.hs:2:1: error:\n\ \ * Couldn't match expected type `IO t0' with actual type `() -> ()'\n\ \ * Probable cause: `main' is applied to too few arguments\n\ \ In the expression: main\n\ \ When checking the type of the IO action `main'\n\ \(deferred type error)"# main :: IO Any [LclIdX, Str=DmdType] main = runMainIO @ Any (main `cast` (Sub cobox_aOD :: ((() -> ()) :: *) ~R# (IO Any :: *))) *** End of Offense *** <no location info>: error: Compilation had errors *** Deleting temp files: Deleting: *** Deleting temp dirs: Deleting: }}} and gcc version is: gcc version 7.1.1 20170516 (GCC) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13838 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler