|Issue 517:||Rule application should not introduce new free variables|
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Given the hint: warn = map (\v -> (v, x)) y ==> zip y (repeat x) If you want it to be correct, you really need to add: where _ = notIn v x However, anything that reduces in a way that introduces a new free variable, i.e: map (\v -> (v, v)) y ==> zip y (repeat v) Here the left has [y] as the free variables, and the right has [y,v], so it doesn't really make sense, and HLint should not apply it. This feature could be introduced by automatically introducing notIn constraints where necessary.
Aug 27, 2013
Done as described, plus I got to remove all notIn hints.
Jan 17, 2014
Released in 1.8.53
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