Scriptable error messages

Simon Peyton-Jones simonpj at
Fri Jan 22 07:13:11 EST 2010

GHC doesn't have any way to let you "plug in" new error messages.  I imagine you mean in the type inference engine?  

Can you characterise more precisely what you want, perhaps by example.  

I do urge you to read the Utrecht work; they have done tremendous stuff on user-defined type rules and associated user-defined error messages.


| -----Original Message-----
| From: glasgow-haskell-users-bounces at [mailto:glasgow-haskell-users-
| bounces at] On Behalf Of Daniel Gustafsson
| Sent: 21 January 2010 18:20
| To: glasgow-haskell-users at
| Subject: Scriptable error messages
| Hello
| Me and a fellow student are taking a course named Frontiers of
| Programming Languages, and in this course we should do a project with
| something. A while ago we were at a presentation of Feldspar, a
| Embedded Domain Specific Language, and one of the negative points of
| using haskell was that the error messages could be cryptic due to the
| various ways it was implemented.
| So we are now looking into the possibility of adding your own error
| messages to GHC as our project. We have about 8 weeks to implement,
| either all or some proof of concept. As such we are looking for
| comments, ideas and suggestions. Is this doable in GHC?, or what is
| needed.
| Thanks
| Daniel Gustafsson
| Simon Edwardsson
| Chalmers University of Technology (Gothenburg, Sweden)
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| Glasgow-haskell-users at

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