existantial types / attempt of using an unObj function/ no type in ghci

[Simon Marlow]

Marc Weber wrote:
> My ghc version: Glasgow Haskell Compiler, Version 6.5.20060117, for Haskell 98, compiled by GHC version 6.5.20060117
> 
> load this into ghci 
> 
> 	module Main where
> 
> 	class Table t where
> 	  tableName :: t ->  String
> 	data TableObj = forall f. (Table f) => TableObj { unObj::f }
> 	instance Table TableObj where
> 	  tableName (TableObj t) = tableName t
> 
> and do :t unObj
> 
> result :
>     marc@(none) ~/projects/haskell/HTTF/Font/TTF $ ghci -fglasgow-exts 
>        ___         ___ _
>       / _ \ /\  /\/ __(_)
>      / /_\// /_/ / /  | |      GHC Interactive, version 6.5.20060117, for Haskell 98.
>     / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
>     \____/\/ /_/\____/|_|      Type :? for help.
> 
>     Loading package base-1.0 ... linking ... done.
>     Prelude> :l Table.hs 
>     [1 of 1] Skipping  Font.TTF.Table   ( Table.hs, Table.o )
>     Ok, modules loaded: Font.TTF.Table.
>     Prelude Font.TTF.Table> :t unObj
> 
>     <interactive>:1:0:
> 	Can't find interface-file declaration for TableObj
> 	  Probable cause: bug in .hi-boot file, or inconsistent .hi file
> 	  Use -ddump-if-trace to get an idea of which file caused the error

This can't be right.  The code you gave above says "module Main", but 
GHCi is loading "Font.TTF.Table", and also it says "Skipping" so there 
is an .hi file lying around too.

Can you tell us how to reproduce the problem starting in an empty directory?

Cheers,
	Simon