Bugs item #1039993, was opened at 2004-10-04 10:41
Message generated for change (Comment added) made by jcast
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Category: Compiler
Group: 6.2.1
Status: Closed
Resolution: Wont Fix
Priority: 5
Submitted By: Jon Cast (jcast)
Assigned to: Nobody/Anonymous (nobody)
Summary: ghc --make + hi-boot + class declarations = trouble
Initial Comment:
Consider the following test case:
-- Main.hs --
module Main where
import Module1
import Module2
main = return ()
-- Module1.hs --
module Module1 where
import Module2
class Three alpha where
three :: Kappa alpha -> Kappa alpha -> Kappa alpha
-- Module1.hi-boot --
module Module2 where
import {-# SOURCE #-} Module1
data Kappa alpha = Kappa alpha alpha
f :: Three alpha => Kappa alpha -> alpha
f k = case three k k of
Kappa x y -> x
-- Module1.hi-boot --
module Module1 where
class Three alpha where
three :: Module2.Kappa alpha -> Module2.Kappa alpha
-> Module2.Kappa alpha
-- Compilation Results --
cd /home/jcast/Source/tmp/ # -*-compilation-*-
Entering directory `/home/jcast/Source/tmp/'
ghc --make Main
Chasing modules from: Main
Compiling Module2 ( ./Module2.hs, ./Module2.o )
./Module2.hs:1:
Failed to find interface decl for `Module1.$dmthree'
from module `Module1'
Compilation exited abnormally with code 1 at Mon Oct 4
09:38:50
No, for the real program it's not strictly necessary to
employ mutual recursion between the modules in
question---but it is by far the most natural design.
----------------------------------------------------------------------
>Comment By: Jon Cast (jcast)
Date: 2004-10-10 17:05
Message:
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Ok, thanks for the clarification.
----------------------------------------------------------------------
Comment By: Simon Peyton Jones (simonpj)
Date: 2004-10-05 03:23
Message:
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You can't put class signatures in a hi-boot file. (The
documentation should say this, and will soon; and the error
message will be better.)
Instead, write the sig for the class op as a separate top-level
defn in the hi-boot file
three :: Three alpha => ...type as before...
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