suggestion: add a .ehs file type

[Alex Jacobson]

Duncan Coutts wrote:
> On Wed, 2007-11-21 at 19:26 -0500, Alex Jacobson wrote:
>> Ok, I'm game to default to haskell98 in the presence of ambiguity, but 
>> in most cases the extension involves new syntax and that should be enough.
> 
> In these cases ghc does generally give an error message which mentions
> which extension it is that you should use. This is actually better than
> the case where you forget to import something when ghc doesn't helpfully
> tell you which module you forgot to import.

My point is that the default should be to give a warning rather than an 
error and provide the user with the ability to turn those warnings off.

> As others have said, one major reason for declaring extensions is for
> portability.

The warning should be enough information for people who want to avoid 
accidentally adding features that will cause their code not to run on 
other compilers.  For those that don't care, forcing them to add 
zillions of pragmas is an excessive burden.

-Alex-