#2307: Poor warning for conflicting functional dependencies
-----------------------------+----------------------------------------------
Reporter: NeilMitchell | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.8.2 | Severity: normal
Keywords: | Testcase:
Architecture: Unknown | Os: Unknown
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{{{
E:\Neil\thesis>ghci obj\haskell2\Proof_default.hs
GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help
Loading package base ... linking ... done.
[1 of 1] Compiling Proof_default ( obj/haskell2/Proof_default.hs,
interpreted
)
obj/haskell2/Proof_default.hs:177:0:
Functional dependencies conflict between instance declarations:
instance [incoherent] SubstRep
(Prop (Sat VarName)) ([VarName], [Expr])
(Prop (Sa
t Expr))
-- Defined at obj/haskell2/Proof_default.hs:177:0-75
instance [incoherent] SubstRep
(Prop (Sat Int)) ([Int], [Expr]) (Prop (Sat
Expr))
-- Defined at obj/haskell2/Proof_default.hs:180:0-67
instance [incoherent] SubstRep
(Prop (Sat Int)) ([Int], [Expr]) (Prop (Sat
Expr))
-- Defined at obj/haskell2/Proof_default.hs:180:0-67
Failed, modules loaded: none.
}}}
It has listed three items that conflict, but two of the items are actually
the same. I would expect the error message to {{{nub}}} the list of
instances first. Sample file attached. This bug may have been fixed in
HEAD, with the recent warnings patch, but I cannot check (not enough disk
space!).
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2307>
GHC <http://www.haskell.org/ghc/>
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