[GHC] #3714: Improve error message if an associated family declaration has excess parameters

[Simon Peyton-Jones]

Indeed.  But do you want to use that syntax for class parameters too?  That would be a big change

	class C {|a|} where ....

S

| -----Original Message-----
| From: Stefan Holdermans [mailto:stefan at cs.uu.nl]
| Sent: 09 December 2009 08:42
| To: glasgow-haskell-bugs at haskell.org
| Cc: Simon Peyton-Jones
| Subject: Re: [GHC] #3714: Improve error message if an associated family
| declaration has excess parameters
| 
| Simon,
| 
| Regarding distinguishing between type indices and parameters, you
| suggested:
| 
| > type family T3 f !e :: *         -- The ! indicates a type parameter
| > (not
| > an index)
| 
| I'd rather have indices, rather than parameters, explicated by mean of
| syntax. This seems more consistent with ordinary type declarations.
| 
| On paper, I often find myself writing
| 
|    type family T3 {|f|} e :: * .
| 
| (A remnant of overexposure to generic programming, I guess.)
| 
| Cheers,
| 
|    Stefan