Avoid isJust/fromJust
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Description
From https://code.google.com/p/ndmitchell/issues/detail?id=238 by @np:
In most situations code like:
if null lst then ... else ... head l ... tail l ...
could be replaced by a case
case lst of [] -> ... ; x : xs -> ... x ... xs ...
Same thing with isJust + fromJust, but maybe could be suggested instead of a case.
@ndmitchell replies:
if isNothing x then 0 else fromJust x + 3
Should suggest:
maybe 0 (+3) x
This relies on having a nice looking functional in the else. Alternatively could have patterns with context, i.e.
if isNothing x then y else _f x ==> maybe x _f x
where _f is the lambda that needs inserting to get it working.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing the issue's isNothing/fromJust examples and the proposed maybe transformation. Define which patterns should trigger a suggestion, including the case where the else branch needs a function, and verify that the resulting suggestion preserves the intended behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- haskell
- Domain
- devtools
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100