Thanks Roberto!
Roberto Zunino wrote:
Chris Kuklewicz wrote:
There is no way to create a "A.hs-boot" file that has all of
(1) Allows A.hs-boot to be compiled without compiling B.hs first
(2) Allows B.hs (with a {-# SOURCE #-} pragma) to be compiled after
A.hs-boot
(3) Allows A.hs to compiled after A.hs-boot with a consistent interface
I thought the following A.hs-boot would suffice:
module A(A) where
data A
There's no need to provide the data constructors for type A. Does this
violate any of the goals above?
Regards,
Zun.
I tried that experiment. The failure is complicated, and triggers be a ghc bug.
Hmmm... the bug for
module A(A) where
data A
deriving Show
using "ghc -c -XGeneralizedNewtypeDeriving A.hs-boot" is
A.hs-boot:2:0:ghc-6.8.3: panic! (the 'impossible' happened)
(GHC version 6.8.3 for powerpc-apple-darwin):
newTyConEtadRhs main:A.A{tc r5z}
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
Is this a known bug?
But now I see that
module A(A(..)) where
import B(B)
data A = A B | End
deriving Show
does work. And avoids the bug!
--
Chris
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