Claus Reinke wrote:
if module 'A' exports multiparameter type classes, importers of those
classes have to have MultiParamTypeClasses on - there are no legal
uses of those imports otherwise (while FlexibleInstances/Contexts can
just affect a subset of use sites).
say we have
module A where { class Coerce a b where coerce :: a -> b }
module B where { import A ; co a = coerce a }
Syntactically, module B doesn't require MultiParamTypeClasses because
the signature that's involved is only discovered during type inference.
Something to beware of if those restrictions need to be implemented
somehow in GHC.
Niklas Broberg wrote:
If there is any interest, I can also propose these cases as bug reports to GHC.
please do!
-Isaac
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