Remove Control.Monad.Error, for transformers-0.6, enabled by mtl-2.3 #141
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The constraints have been reorganized according to these principles: - mention dependency on top-level if mentioned in all branches of a conditional - do not repeat constraints in test-suite that are inherited from library - order each dependency group alphabetically (but `base` and parent go first) - format with leading comma (harder to make mistakes) - align at >= and &&
find . -name "*hs" | xargs fix-whitespace
instance Monad (Either e) isn't found when compiling with base <= 4.5
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This looks good to me and I think dropping the old GHCs is overdue. Probably time for a major version bump (i.e. to |
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@hsenag wrote:
Indeed, removal of
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Good point! |
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Remove
Control.Monad.Error, fortransformers-0.6, enabled bymtl-2.3.This breaks compilation with
base <= 4.5so I bumped the lower base to4.6.I tried to preserve compilation with
base <= 4.5, but my attempts failed: no instance forMonad Result, whereResult = Either <SomeTypeOfErrors>.I suppose this instance was provided via a
Monadinstance forEitherwith anErrorconstraint in olderbaseversions.I tried these fixes to no avail:
Data.EitherorControl.Monad.Instance: But this did not help, presumably because anErrorconstraint is needed? (Hard to get the history of theinstance Monad (Either _), docs only show since base-4.4, but its definition could have changed.)I have not tried
base-compatinstance Monad Result: this is also hairy across GHC versions as:MonadchangedIf it is important to preserve GHC 7.0-7.4 in new releases of HTTP, one could try harder.
But maybe it is ok to drop these. Legacy GHCs can use older versions of HTTP.
This PR is based on #140.