[Haskell-cafe] resolving missing class instances @ compile time

[Greg Buchholz]

Samuel Bronson wrote:
> Aren't the warnings just about as usefull as failures? Anyway, you
> could always use the -Werrror flag for ghc...
> 
> In any case, I would not like to have to implement an entire typeclass
> at once... it would interfere with incremental development.

    Hmm.  I guess I'm doing a terrible job of asking my question.  I
don't want to implement the entire typeclass either.  Just the part that
my program actually uses.  Why can't the fact that my program uses an
unimplemented instance of a class be statically determined?  Is there a
theoretical reason it can't be done?  Is it more convienient for
compiler/specification writers this way?  Is it just because that's the
way its always been done?


Curious,

Greg Buchholz