#9025: Core Lint warning with -O (Demand type has 4 arguments ...)
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Reporter: conal | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.8.2
Keywords: | Operating System: Unknown/Multiple
Architecture: Unknown/Multiple | Type of failure: None/Unknown
Difficulty: Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: |
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The attached small program triggers a Core Lint warning when compiled with
`-O`:
{{{
bash-3.2$ ghc LintBomb.hs -fforce-recomp -dcore-lint
[1 of 1] Compiling LintBomb ( LintBomb.hs, LintBomb.o )
bash-3.2$ ghc LintBomb.hs -fforce-recomp -dcore-lint -O
[1 of 1] Compiling LintBomb ( LintBomb.hs, LintBomb.o )
*** Core Lint errors : in result of CorePrep ***
{-# LINE 13 "LintBomb.hs #-}: Warning:
[RHS of LintBomb.$fEncodable(->)_$cencode :: forall a_arW b_arX.
(LintBomb.Encodable
a_arW,
LintBomb.Encodable
b_arX) =>
(a_arW -> b_arX) ->
LintBomb.Enc (a_arW -> b_arX)]
Demand type has 4 arguments, rhs has 3 arguments,
LintBomb.$fEncodable(->)_$cencode
Binder's strictness signature: DmdType
*** Offending Program ***
LintBomb.encode [InlPrag=[NEVER]]
:: forall a_arV.
LintBomb.Encodable a_arV =>
a_arV -> LintBomb.Enc a_arV
[GblId[ClassOp],
Arity=1,
Caf=NoCafRefs,
Str=DmdType ,
Unf=OtherCon [],
RULES: Built in rule for LintBomb.encode: "Class op encode"]
LintBomb.encode =
\ (@ a_arV) (tpl_sOv [Occ=Once!] :: LintBomb.Encodable a_arV) ->
case tpl_sOv
of _ [Occ=Dead]
{ LintBomb.D:Encodable tpl_sOx [Occ=Once] _ [Occ=Dead] ->
tpl_sOx
}
LintBomb.decode [InlPrag=[NEVER]]
:: forall a_arV.
LintBomb.Encodable a_arV =>
LintBomb.Enc a_arV -> a_arV
[GblId[ClassOp],
Arity=1,
Caf=NoCafRefs,
Str=DmdType ,
Unf=OtherCon [],
RULES: Built in rule for LintBomb.decode: "Class op decode"]
LintBomb.decode =
\ (@ a_arV) (tpl_sOz [Occ=Once!] :: LintBomb.Encodable a_arV) ->
case tpl_sOz
of _ [Occ=Dead]
{ LintBomb.D:Encodable _ [Occ=Dead] tpl_sOC [Occ=Once] ->
tpl_sOC
}
LintBomb.$fEncodable(->)_$cdecode
:: forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
LintBomb.Enc (a_arW -> b_arX) -> a_arW -> b_arX
[GblId,
Arity=4,
Caf=NoCafRefs,
Str=DmdType ,
Unf=OtherCon []]
LintBomb.$fEncodable(->)_$cdecode =
\ (@ a_arW)
(@ b_arX)
($dEncodable_sOD [Occ=Once] :: LintBomb.Encodable a_arW)
($dEncodable1_sOE [Occ=Once] :: LintBomb.Encodable b_arX)
(h_sOF [Occ=Once] :: LintBomb.Enc (a_arW -> b_arX))
(eta_sOG [Occ=Once] :: a_arW) ->
let {
sat_sOI [Occ=Once] :: LintBomb.Enc b_arX
[LclId, Str=DmdType]
sat_sOI =
let {
sat_sOH [Occ=Once] :: LintBomb.Enc a_arW
[LclId, Str=DmdType]
sat_sOH = LintBomb.encode @ a_arW $dEncodable_sOD eta_sOG } in
(h_sOF
`cast` (Sub (LintBomb.TFCo:R:Enc(->)[0] _N _N)
:: LintBomb.Enc (a_arW -> b_arX)
~#
(LintBomb.Enc a_arW -> LintBomb.Enc b_arX)))
sat_sOH } in
LintBomb.decode @ b_arX $dEncodable1_sOE sat_sOI
LintBomb.$fEncodable(->)1
:: forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
(a_arW -> b_arX) -> LintBomb.Enc a_arW -> LintBomb.Enc b_arX
[GblId,
Arity=4,
Caf=NoCafRefs,
Str=DmdType ,
Unf=OtherCon []]
LintBomb.$fEncodable(->)1 =
\ (@ a_arW)
(@ b_arX)
($dEncodable_sOJ [Occ=Once] :: LintBomb.Encodable a_arW)
($dEncodable1_sOK [Occ=Once] :: LintBomb.Encodable b_arX)
(f_sOL [Occ=Once!] :: a_arW -> b_arX)
(eta_sOM [Occ=Once] :: LintBomb.Enc a_arW) ->
let {
sat_sOO [Occ=Once] :: b_arX
[LclId, Str=DmdType]
sat_sOO =
let {
sat_sON [Occ=Once] :: a_arW
[LclId, Str=DmdType]
sat_sON = LintBomb.decode @ a_arW $dEncodable_sOJ eta_sOM } in
f_sOL sat_sON } in
LintBomb.encode @ b_arX $dEncodable1_sOK sat_sOO
LintBomb.$fEncodable(->)_$cencode
:: forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
(a_arW -> b_arX) -> LintBomb.Enc (a_arW -> b_arX)
[GblId,
Arity=3,
Caf=NoCafRefs,
Str=DmdType ,
Unf=OtherCon []]
LintBomb.$fEncodable(->)_$cencode =
(\ (@ a_arW)
(@ b_arX)
(eta_B3 [Occ=Once] :: LintBomb.Encodable a_arW)
(eta_B2 [Occ=Once] :: LintBomb.Encodable b_arX)
(eta_B1 [Occ=Once] :: a_arW -> b_arX) ->
LintBomb.$fEncodable(->)1 @ a_arW @ b_arX eta_B3 eta_B2 eta_B1)
`cast` (forall a_arW b_arX.
_R
-> _R
-> b_arX>_R
-> Sub (Sym (LintBomb.TFCo:R:Enc(->)[0] _N _N))
:: (forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
(a_arW -> b_arX) -> LintBomb.Enc a_arW -> LintBomb.Enc
b_arX)
~#
(forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
(a_arW -> b_arX) -> LintBomb.Enc (a_arW -> b_arX)))
LintBomb.$fEncodable(->) [InlPrag=[ALWAYS] CONLIKE]
:: forall a_arW b_arX.
(LintBomb.Encodable a_arW, LintBomb.Encodable b_arX) =>
LintBomb.Encodable (a_arW -> b_arX)
[GblId[DFunId],
Arity=2,
Caf=NoCafRefs,
Str=DmdType m,
Unf=OtherCon []]
LintBomb.$fEncodable(->) =
\ (@ a_Xs8)
(@ b_Xsa)
($dEncodable_sOP :: LintBomb.Encodable a_Xs8)
($dEncodable1_sOQ :: LintBomb.Encodable b_Xsa) ->
let {
sat_sOS [Occ=Once]
:: LintBomb.Enc (a_Xs8 -> b_Xsa) -> a_Xs8 -> b_Xsa
[LclId, Str=DmdType]
sat_sOS =
\ (eta_B2 [Occ=Once] :: LintBomb.Enc (a_Xs8 -> b_Xsa))
(eta_B1 [Occ=Once] :: a_Xs8) ->
LintBomb.$fEncodable(->)_$cdecode
@ a_Xs8 @ b_Xsa $dEncodable_sOP $dEncodable1_sOQ eta_B2 eta_B1
} in
let {
sat_sOR [Occ=Once]
:: (a_Xs8 -> b_Xsa) -> LintBomb.Enc (a_Xs8 -> b_Xsa)
[LclId, Str=DmdType]
sat_sOR =
(\ (eta_B1 [Occ=Once] :: a_Xs8 -> b_Xsa) ->
LintBomb.$fEncodable(->)1
@ a_Xs8 @ b_Xsa $dEncodable_sOP $dEncodable1_sOQ eta_B1)
`cast` ( b_Xsa>_R
-> Sub (Sym (LintBomb.TFCo:R:Enc(->)[0] _N
_N))
:: ((a_Xs8 -> b_Xsa) -> LintBomb.Enc a_Xs8 -> LintBomb.Enc
b_Xsa)
~#
((a_Xs8 -> b_Xsa) -> LintBomb.Enc (a_Xs8 -> b_Xsa))) }
in
LintBomb.D:Encodable @ (a_Xs8 -> b_Xsa) sat_sOR sat_sOS
LintBomb.D:Encodable
:: forall a_arV.
(a_arV -> LintBomb.Enc a_arV)
-> (LintBomb.Enc a_arV -> a_arV) -> LintBomb.Encodable a_arV
[GblId[DataCon],
Arity=2,
Caf=NoCafRefs,
Str=DmdType m,
Unf=OtherCon []]
LintBomb.D:Encodable =
\ (@ a_arV)
(eta_B2 [Occ=Once] :: a_arV -> LintBomb.Enc a_arV)
(eta_B1 [Occ=Once] :: LintBomb.Enc a_arV -> a_arV) ->
LintBomb.D:Encodable @ a_arV eta_B2 eta_B1
*** End of Offense ***
<no location info>:
Compilation had errors
}}}
--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9025
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
