Refactor: Clean up CanHold(Un)Signed instances #22
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Avoided redundant transitive instances by doing type-level natural number comparisons Use custom type errors to explain why the instance is not available The downside is that the constraints are not extensible - i.e: users cannot create their own instances for their own numeric types. I think the only way to solve this while keeping the nice type errors would be to rely on overlapping instances (but there might be a trick that I am unaware of)
|
I think messed up the PR, again, sorry lol |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Note that GHC now (as of
9.8.1) supports a slightly more principled way of adding custom type errors viaUnsatisfiableconstraints. The main trouble with trying to use it isBitWidth(which doesn't returnConstraint). We could create another constraint family with an appropriate error message, or perhaps have it take ab :: Bitsstanding for the return value and return equality constraints (b ~ B8/b ~ B16, etc...) in the successful cases, hoping Haskell's constraint solver makes everything work out nicely.