-Wdeferred-type-errors on a program with main not of type IO () yields "main thread exited (uncaught exception)"
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
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)
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |