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[GHC] #6046: inconsistent type error messages between ghc and ghci

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[GHC] #6046: inconsistent type error messages between ghc and ghci

#6046: inconsistent type error messages between ghc and ghci
-----------------------------------------+----------------------------------
Reporter: carter | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.5 | Keywords:
Os: MacOS X | Architecture: x86_64 (amd64)
Failure: Incorrect result at runtime | Testcase: see problem description
Blockedby: | Blocking:
Related: |
-----------------------------------------+----------------------------------
When building syb 0.3.6 with todays head / 7.5
I get different type error messages for the module Data/Generics/Twins.hs
respectively from ghc when doing cabal install syb vs when i load that
module into ghci

ghc:

src/Data/Generics/Twins.hs:202:14:
Illegal polymorphic or qualified type: GenericT
Perhaps you intended to use -XRankNTypes or -XRank2Types
In the type signature for `gzipWithT':
gzipWithT :: GenericQ (GenericT) -> GenericQ (GenericT)

src/Data/Generics/Twins.hs:213:14:
Illegal polymorphic or qualified type: GenericM m
Perhaps you intended to use -XRankNTypes or -XRank2Types
In the type signature for `gzipWithM':
gzipWithM :: Monad m =>
GenericQ (GenericM m) -> GenericQ (GenericM m)

src/Data/Generics/Twins.hs:223:14:
Illegal polymorphic or qualified type: GenericQ r
Perhaps you intended to use -XRankNTypes or -XRank2Types
In the type signature for `gzipWithQ':
gzipWithQ :: GenericQ (GenericQ r) -> GenericQ (GenericQ [r])

src/Data/Generics/Twins.hs:265:9:
Illegal polymorphic or qualified type: GenericM Maybe
Perhaps you intended to use -XRankNTypes or -XRank2Types
In the type signature for `gzip':
gzip :: GenericQ (GenericM Maybe) -> GenericQ (GenericM Maybe)

--- interestingly, rank2types is infact enabled in that module.

whereas when the module is loaded into ghci, I get a very different error
message

Loading package base ... linking ... done.
[1 of 2] Compiling Data.Generics.Aliases ( Data/Generics/Aliases.hs,
interpreted )
[2 of 2] Compiling Data.Generics.Twins ( Data/Generics/Twins.hs,
interpreted )

Data/Generics/Twins.hs:118:12: Not in scope: type variable `b'

Data/Generics/Twins.hs:118:17: Not in scope: type variable `a'

Data/Generics/Twins.hs:118:39: Not in scope: type variable `b'

Data/Generics/Twins.hs:118:42: Not in scope: type variable `a'

----
irrespective of fixing the type error (i hope to sort that out this
evening),
the type error message should be the same between ghc and ghci in this
instance right?

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6046>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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Re: [GHC] #6046: inconsistent type error messages between ghc and ghci

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#6046: inconsistent type error messages between ghc and ghci
----------------------------------------+-----------------------------------
Reporter: carter | Owner:
Type: bug | Status: closed
Priority: normal | Component: Compiler
Version: 7.5 | Resolution: invalid
Keywords: | Os: MacOS X
Architecture: x86_64 (amd64) | Failure: Incorrect result at runtime
Testcase: see problem description | Blockedby:
Blocking: | Related:
----------------------------------------+-----------------------------------
Changes (by dreixel):

* status: new => closed
* resolution: => invalid

Comment:

The syb.cabal file (see
http://hackage.haskell.org/packages/archive/syb/0.3.6/syb.cabal) mentions
the extension `ScopedTypeVariables`, but if you load the file on GHCi you
won't get this. This explains the difference in behaviour between `cabal
install` and just loading the file on GHCi.

The `RankNTypes` error itself is already reported as #6032. I think the
best thing to do is to change `syb`; I'll release an updated version
today.

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6046#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

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