Re: ghci confused by hi files

[Yitzchak Gale]

I wrote:

I have observed the following weird behavior:
...ghci's ability to recognize the
methods of the class seems to vary depending
on whether or not hi files exist for the modules.


Daniel Fischer wrote:

Pertinent to this is section 3.4.3 of the user's guide, What's really in
scope at the prompt.
For compiled modules, only the exports of these are in scope.
So this is documented behaviour.


OK, thanks, I see that now. But I would have only expected
that to apply to modules that are _only_ compiled. If the
source code is also available, why should I be penalized
for compiling it?

Preferring the source code over the compiled code by
default would be much more convenient for iterative
debugging. But if that cannot be the default, it would
be nice if it were at least an option.

Thanks,
Yitz
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ghci confused by hi files

[Yitzchak Gale]

I have observed the following weird behavior:

When I define an instance of a certain MPTC
in a separate module from the definition of
the class, ghci's ability to recognize the
methods of the class seems to vary depending
on whether or not hi files exist for the modules.

I am using the current Debian build of GHC 6.6.

Below are a set of three files that reproduce the
behavior, and a shell session that demonstrates
it.

Before I compile the program, ghci works fine.
After I compile with ghc  - thus generating hi files -
ghci gets confused. Then I delete the hi files
and everything is fine again.

Thanks,
Yitz

-- File Oops.hs

{-# OPTIONS_GHC -fglasgow-exts #-}
module Oops where
class Oops a b c | a - b c where
 foo :: a - b - a

-- File Whoops.hs

{-# OPTIONS_GHC -fglasgow-exts #-}
module Whoops where
import Oops
instance Oops String Int Bool where
 foo x n = show (x, n)

-- File runWhoops.hs

module Main where
import Whoops
import Oops
main = putStrLn $ foo bar 42

$ ghci Whoops
/ /_\// /_/ / /  | |  GHC Interactive, version 6.6, for Haskell 98.
Loading package base ... linking ... done.
[1 of 2] Compiling Oops ( Oops.hs, interpreted )
[2 of 2] Compiling Whoops   ( Whoops.hs, interpreted )
Ok, modules loaded: Oops, Whoops.
*Whoops foo baz 7
(\baz\,7)
*Whoops Leaving GHCi.
$ ghc --make runWhoops.hs
[1 of 3] Compiling Oops ( Oops.hs, Oops.o )
[2 of 3] Compiling Whoops   ( Whoops.hs, Whoops.o )
[3 of 3] Compiling Main ( runWhoops.hs, runWhoops.o )
Linking runWhoops ...
$ ghci Whoops
/ /_\// /_/ / /  | |  GHC Interactive, version 6.6, for Haskell 98.
Loading package base ... linking ... done.
Ok, modules loaded: Oops, Whoops.
Prelude Whoops foo baz 7

interactive:1:0: Not in scope: `foo'
Prelude Whoops Leaving GHCi.
$ rm *.hi
$ ghci Whoops
/ /_\// /_/ / /  | |  GHC Interactive, version 6.6, for Haskell 98.
Loading package base ... linking ... done.
[1 of 2] Compiling Oops ( Oops.hs, interpreted )
[2 of 2] Compiling Whoops   ( Whoops.hs, interpreted )
Ok, modules loaded: Oops, Whoops.
*Whoops foo baz 7
(\baz\,7)
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