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hlint.yaml
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hlint.yaml
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# hlint configuration file
# ==================================
# The hlint tool is mainly automatic, but some hints/restrictions can be specified here.
- package:
name: base
modules:
- import Control.Applicative
- import Control.Arrow
- import Control.Concurrent.Chan
- import Control.Exception
- import Control.Exception.Base
- import Control.Monad
- import Control.Monad.Trans.State
- import Data.Bifunctor
- import Data.Char
- import Data.Either
- import Data.Fixed
- import Data.Foldable(asum, sequenceA_, traverse_, for_)
- import Data.Function
- import Data.Int
- import Data.List as Data.List
- import Data.List as X
- import Data.List.NonEmpty
- import Data.Maybe
- import Data.Monoid
- import Data.Ratio
- import Data.Traversable(traverse, for)
- import Numeric
- import Prelude
- import System.Exit
- import System.IO
- import System.Mem.Weak
- import Text.Read
- import qualified Data.Foldable
- import IO as System.IO
- import List as Data.List
- import Maybe as Data.Maybe
- import Monad as Control.Monad
- import Char as Data.Char
- import Language.Haskell.TH as TH
- package:
name: lens
modules:
- import Control.Lens
- import Control.Lens.Operators
- import Control.Monad.Reader
- package:
name: attoparsec
modules:
- import Data.Attoparsec.Text
- import Data.Attoparsec.ByteString
- package:
name: quickcheck
modules:
- import Test.QuickCheck
- package:
name: codeworld-api
modules:
- import CodeWorld
- group:
name: default
enabled: true
imports:
- package base
rules:
# I/O
- warn: {lhs: putStrLn (show x), rhs: print x}
- warn: {lhs: putStr (x ++ "\n"), rhs: putStrLn x}
- warn: {lhs: putStr (x ++ y ++ "\n"), rhs: putStrLn (x ++ y)}
- warn: {lhs: mapM_ putChar, rhs: putStr}
- warn: {lhs: hGetChar stdin, rhs: getChar}
- warn: {lhs: hGetLine stdin, rhs: getLine}
- warn: {lhs: hGetContents stdin, rhs: getContents}
- warn: {lhs: hPutChar stdout, rhs: putChar}
- warn: {lhs: hPutStr stdout, rhs: putStr}
- warn: {lhs: hPutStrLn stdout, rhs: putStrLn}
- warn: {lhs: hPrint stdout, rhs: print}
- warn: {lhs: hWaitForInput a 0, rhs: hReady a}
- warn: {lhs: hPutStrLn a (show b), rhs: hPrint a b}
- warn: {lhs: hIsEOF stdin, rhs: isEOF}
- warn: {lhs: withFile f WriteMode (\h -> hPutStr h x), rhs: writeFile f x}
- warn: {lhs: withFile f WriteMode (\h -> hPutStrLn h x), rhs: writeFile f (x ++ "\n")}
- warn: {lhs: withFile f AppendMode (\h -> hPutStr h x), rhs: appendFile f x}
- warn: {lhs: withFile f AppendMode (\h -> hPutStrLn h x), rhs: appendFile f (x ++ "\n")}
# EXIT
- warn: {lhs: exitWith ExitSuccess, rhs: exitSuccess}
# ORD
- warn: {lhs: not (a == b), rhs: a /= b, note: incorrect if either value is NaN}
- warn: {lhs: not (a /= b), rhs: a == b, note: incorrect if either value is NaN}
- warn: {lhs: not (a > b), rhs: a <= b, note: incorrect if either value is NaN}
- warn: {lhs: not (a >= b), rhs: a < b, note: incorrect if either value is NaN}
- warn: {lhs: not (a < b), rhs: a >= b, note: incorrect if either value is NaN}
- warn: {lhs: not (a <= b), rhs: a > b, note: incorrect if either value is NaN}
- warn: {lhs: compare x y /= GT, rhs: x <= y}
- warn: {lhs: compare x y == LT, rhs: x < y}
- warn: {lhs: compare x y /= LT, rhs: x >= y}
- warn: {lhs: compare x y == GT, rhs: x > y}
- warn: {lhs: compare x y == EQ, rhs: x == y}
- warn: {lhs: compare x y /= EQ, rhs: x /= y}
- warn: {lhs: head (sort x), rhs: minimum x}
- warn: {lhs: last (sort x), rhs: maximum x}
- warn: {lhs: head (sortBy f x), rhs: minimumBy f x, side: isCompare f}
- warn: {lhs: last (sortBy f x), rhs: maximumBy f x, side: isCompare f}
- warn: {lhs: reverse (sortBy f x), rhs: sortBy (flip f) x, name: Avoid reverse, side: isCompare f, note: Stabilizes sort order}
- warn: {lhs: sortBy (flip (comparing f)), rhs: sortBy (comparing (Data.Ord.Down . f))}
- warn: {lhs: reverse (sortOn f x), rhs: sortOn (Data.Ord.Down . f) x, name: Avoid reverse, note: Stabilizes sort order}
- warn: {lhs: reverse (sort x), rhs: sortBy (comparing Data.Ord.Down) x, name: Avoid reverse, note: Stabilizes sort order}
- hint: {lhs: flip (g `on` h), rhs: flip g `on` h, name: Move flip}
- hint: {lhs: (f `on` g) `on` h, rhs: f `on` (g . h), name: Fuse on/on}
- warn: {lhs: if a >= b then a else b, rhs: max a b}
- warn: {lhs: if a >= b then b else a, rhs: min a b}
- warn: {lhs: if a > b then a else b, rhs: max a b}
- warn: {lhs: if a > b then b else a, rhs: min a b}
- warn: {lhs: if a <= b then a else b, rhs: min a b}
- warn: {lhs: if a <= b then b else a, rhs: max a b}
- warn: {lhs: if a < b then a else b, rhs: min a b}
- warn: {lhs: if a < b then b else a, rhs: max a b}
- warn: {lhs: "maximum [a, b]", rhs: max a b}
- warn: {lhs: "minimum [a, b]", rhs: min a b}
# READ/SHOW
- warn: {lhs: showsPrec 0 x "", rhs: show x}
- warn: {lhs: "showsPrec 0 x []", rhs: show x}
- warn: {lhs: readsPrec 0, rhs: reads}
- warn: {lhs: showsPrec 0, rhs: shows}
- hint: {lhs: showIntAtBase 16 intToDigit, rhs: showHex}
- hint: {lhs: showIntAtBase 8 intToDigit, rhs: showOct}
# LIST
- warn: {lhs: concat (map f x), rhs: concatMap f x}
- warn: {lhs: concat (f <$> x), rhs: concatMap f x}
- warn: {lhs: concat (x <&> f), rhs: concatMap f x}
- warn: {lhs: concat (fmap f x), rhs: concatMap f x}
- hint: {lhs: "concat [a, b]", rhs: a ++ b}
- hint: {lhs: map f (map g x), rhs: map (f . g) x, name: Use map once}
- hint: {lhs: concatMap f (map g x), rhs: concatMap (f . g) x, name: Fuse concatMap/map}
- hint: {lhs: x !! 0, rhs: head x}
- warn: {lhs: take n (repeat x), rhs: replicate n x}
- warn: {lhs: map f (replicate n x), rhs: replicate n (f x)}
- warn: {lhs: map f (repeat x), rhs: repeat (f x)}
- warn: {lhs: concatMap f (repeat x), rhs: cycle (f x)}
- warn: {lhs: concat (repeat x), rhs: cycle x}
- warn: {lhs: "cycle [x]", rhs: repeat x}
- warn: {lhs: head (reverse x), rhs: last x}
- warn: {lhs: last (reverse x), rhs: head x, note: IncreasesLaziness}
- warn: {lhs: head (drop n x), rhs: x !! n, side: isNat n}
- warn: {lhs: head (drop n x), rhs: x !! max 0 n, side: not (isNat n) && not (isNeg n)}
- warn: {lhs: reverse (init x), rhs: tail (reverse x)}
- warn: {lhs: reverse (tail (reverse x)), rhs: init x, note: IncreasesLaziness}
- warn: {lhs: reverse (reverse x), rhs: x, note: IncreasesLaziness, name: Avoid reverse}
- warn: {lhs: isPrefixOf (reverse x) (reverse y), rhs: isSuffixOf x y}
- warn: {lhs: "foldr (++) []", rhs: concat}
- warn: {lhs: foldr (++) "", rhs: concat}
- warn: {lhs: "foldr ((++) . f) []", rhs: concatMap f}
- warn: {lhs: foldr ((++) . f) "", rhs: concatMap f}
- warn: {lhs: "foldl (++) []", rhs: concat, note: IncreasesLaziness}
- warn: {lhs: foldl (++) "", rhs: concat, note: IncreasesLaziness}
- warn: {lhs: foldl f (head x) (tail x), rhs: foldl1 f x}
- warn: {lhs: foldr f (last x) (init x), rhs: foldr1 f x}
- warn: {lhs: "foldr (\\c a -> x : a) []", rhs: "map (\\c -> x)"}
- warn: {lhs: foldr (.) id l z, rhs: foldr ($) z l}
- warn: {lhs: span (not . p), rhs: break p}
- warn: {lhs: break (not . p), rhs: span p}
- warn: {lhs: span (notElem x), rhs: break (elem x), name: Use break}
- warn: {lhs: break (notElem x), rhs: span (elem x), name: Use span}
- warn: {lhs: "(takeWhile p x, dropWhile p x)", rhs: span p x, note: DecreasesLaziness}
- warn: {lhs: fst (span p x), rhs: takeWhile p x}
- warn: {lhs: snd (span p x), rhs: dropWhile p x}
- warn: {lhs: fst (break p x), rhs: takeWhile (not . p) x}
- warn: {lhs: snd (break p x), rhs: dropWhile (not . p) x}
- warn: {lhs: "(take n x, drop n x)", rhs: splitAt n x, note: DecreasesLaziness}
- warn: {lhs: fst (splitAt p x), rhs: take p x}
- warn: {lhs: snd (splitAt p x), rhs: drop p x}
- warn: {lhs: concatMap (++ "\n"), rhs: unlines}
- warn: {lhs: map id, rhs: id}
- warn: {lhs: concatMap id, rhs: concat}
- warn: {lhs: or (map p x), rhs: any p x}
- warn: {lhs: and (map p x), rhs: all p x}
- warn: {lhs: any f (map g x), rhs: any (f . g) x}
- warn: {lhs: all f (map g x), rhs: all (f . g) x}
- warn: {lhs: "zipWith (,)", rhs: zip}
- warn: {lhs: "zipWith3 (,,)", rhs: zip3}
- hint: {lhs: map fst &&& map snd, rhs: unzip}
- hint: {lhs: length x == 0, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: 0 == length x, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: length x < 1, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: 1 > length x, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: length x <= 0, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: 0 >= length x, rhs: null x, note: IncreasesLaziness}
- hint: {lhs: "x == []", rhs: null x}
- hint: {lhs: "[] == x", rhs: null x}
- hint: {lhs: all (const False), rhs: "null"}
- hint: {lhs: any (const True) x, rhs: not (null x), name: Use null}
- hint: {lhs: length x /= 0, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- hint: {lhs: 0 /= length x, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- hint: {lhs: "\\x -> [x]", rhs: "(:[])", name: "Use :"}
- hint: {lhs: map f (zip x y), rhs: zipWith (curry f) x y, side: not (isApp f)}
- hint: {lhs: "map f (fromMaybe [] x)", rhs: "maybe [] (map f) x"}
- hint: {lhs: "concatMap f (fromMaybe [] x)", rhs: "maybe [] (concatMap f) x"}
- hint: {lhs: "concat (fromMaybe [] x)", rhs: "maybe [] concat x"}
- warn: {lhs: not (elem x y), rhs: notElem x y}
- warn: {lhs: not (notElem x y), rhs: elem x y}
- hint: {lhs: foldr f z (map g x), rhs: foldr (f . g) z x, name: Fuse foldr/map}
- warn: {lhs: "x ++ concatMap (' ':) y", rhs: "unwords (x:y)"}
- warn: {lhs: intercalate " ", rhs: unwords}
- hint: {lhs: concat (intersperse x y), rhs: intercalate x y, side: notEq x " "}
- hint: {lhs: concat (intersperse " " x), rhs: unwords x}
- warn: {lhs: null (concat x), rhs: all null x}
- warn: {lhs: null (filter f x), rhs: not (any f x), name: Use any}
- warn: {lhs: "filter f x == []", rhs: not (any f x), name: Use any}
- warn: {lhs: "filter f x /= []", rhs: any f x}
- warn: {lhs: any id, rhs: or}
- warn: {lhs: all id, rhs: and}
- warn: {lhs: any (not . f) x, rhs: not (all f x), name: Hoist not}
- warn: {lhs: all (not . f) x, rhs: not (any f x), name: Hoist not}
- warn: {lhs: any ((==) a), rhs: elem a, note: ValidInstance Eq a}
- warn: {lhs: any (== a), rhs: elem a}
- warn: {lhs: any (a ==), rhs: elem a, note: ValidInstance Eq a}
- warn: {lhs: all ((/=) a), rhs: notElem a, note: ValidInstance Eq a}
- warn: {lhs: all (/= a), rhs: notElem a, note: ValidInstance Eq a}
- warn: {lhs: all (a /=), rhs: notElem a, note: ValidInstance Eq a}
- warn: {lhs: elem True, rhs: or}
- warn: {lhs: notElem False, rhs: and}
- warn: {lhs: True `elem` l, rhs: or l}
- warn: {lhs: False `notElem` l, rhs: and l}
- warn: {lhs: elem False, rhs: any not, name: Use any}
- warn: {lhs: notElem True, rhs: all not, name: Use all}
- warn: {lhs: False `elem` l, rhs: any not l, name: Use any}
- warn: {lhs: True `notElem` l, rhs: all not l, name: Use all}
- warn: {lhs: findIndex ((==) a), rhs: elemIndex a}
- warn: {lhs: findIndex (a ==), rhs: elemIndex a}
- warn: {lhs: findIndex (== a), rhs: elemIndex a}
- warn: {lhs: findIndices ((==) a), rhs: elemIndices a}
- warn: {lhs: findIndices (a ==), rhs: elemIndices a}
- warn: {lhs: findIndices (== a), rhs: elemIndices a}
- warn: {lhs: "lookup b (zip l [0..])", rhs: elemIndex b l}
- hint: {lhs: "elem x [y]", rhs: x == y, note: ValidInstance Eq a}
- hint: {lhs: "notElem x [y]", rhs: x /= y, note: ValidInstance Eq a}
- hint: {lhs: "length [1..n]", rhs: max 0 n}
- hint: {lhs: length x >= 0, rhs: "True", name: Length always non-negative}
- hint: {lhs: 0 <= length x, rhs: "True", name: Length always non-negative}
- hint: {lhs: length x > 0, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- hint: {lhs: 0 < length x, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- hint: {lhs: length x >= 1, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- hint: {lhs: 1 <= length x, rhs: not (null x), note: IncreasesLaziness, name: Use null}
- warn: {lhs: take i x, rhs: "[]", side: isNegZero i, name: Take on a non-positive}
- warn: {lhs: drop i x, rhs: x, side: isNegZero i, name: Drop on a non-positive}
- warn: {lhs: last (scanl f z x), rhs: foldl f z x}
- warn: {lhs: head (scanr f z x), rhs: foldr f z x}
- warn: {lhs: "scanl (\\x _ -> a) b (replicate c d)", rhs: "take c (iterate (\\x -> a) b)"}
- warn: {lhs: "foldl (\\x _ -> a) b [1..c]", rhs: "iterate (\\x -> a) b !! c"}
- warn: {lhs: iterate id, rhs: repeat}
- warn: {lhs: zipWith f (repeat x), rhs: map (f x)}
- warn: {lhs: zip (repeat x), rhs: "map (_noParen_ x,)", note: RequiresExtension TupleSections, name: "Use map with tuple-section"}
- warn: {lhs: zipWith f y (repeat z), rhs: map (`f` z) y}
- warn: {lhs: zip y (repeat z), rhs: "map (,_noParen_ z) y", note: RequiresExtension TupleSections, name: "Use map with tuple-section"}
- warn: {lhs: listToMaybe (filter p x), rhs: find p x}
- warn: {lhs: zip (take n x) (take n y), rhs: take n (zip x y)}
- warn: {lhs: zip (take n x) (take m y), rhs: take (min n m) (zip x y), side: notEq n m, note: [IncreasesLaziness, DecreasesLaziness], name: Redundant take}
# MONOIDS
- warn: {lhs: mempty <> x, rhs: x, name: "Monoid law, left identity"}
- warn: {lhs: mempty `mappend` x, rhs: x, name: "Monoid law, left identity"}
- warn: {lhs: x <> mempty, rhs: x, name: "Monoid law, right identity"}
- warn: {lhs: x `mappend` mempty, rhs: x, name: "Monoid law, right identity"}
- warn: {lhs: foldr (<>) mempty, rhs: Data.Foldable.fold}
- warn: {lhs: foldr mappend mempty, rhs: Data.Foldable.fold}
- warn: {lhs: mempty x, rhs: mempty, name: Evaluate}
- warn: {lhs: x `mempty` y, rhs: mempty, name: Evaluate, note: "Make sure you didn't mean to use mappend instead of mempty"}
# TRAVERSABLES
- warn: {lhs: traverse pure, rhs: pure, name: "Traversable law"}
- warn: {lhs: traverse (pure . f) x, rhs: pure (fmap f x), name: "Traversable law"}
- warn: {lhs: sequenceA (map f x), rhs: traverse f x}
- warn: {lhs: sequenceA (f <$> x), rhs: traverse f x}
- warn: {lhs: sequenceA (x <&> f), rhs: traverse f x}
- warn: {lhs: sequenceA (fmap f x), rhs: traverse f x}
- warn: {lhs: sequenceA_ (map f x), rhs: traverse_ f x}
- warn: {lhs: sequenceA_ (f <$> x), rhs: traverse_ f x}
- warn: {lhs: sequenceA_ (x <&> f), rhs: traverse_ f x}
- warn: {lhs: sequenceA_ (fmap f x), rhs: traverse_ f x}
- warn: {lhs: foldMap id, rhs: fold}
- warn: {lhs: fold (f <$> x), rhs: foldMap f x}
- warn: {lhs: fold (x <&> f), rhs: foldMap f x}
- warn: {lhs: fold (fmap f x), rhs: foldMap f x}
- warn: {lhs: fold (map f x), rhs: foldMap f x}
- warn: {lhs: foldMap f (g <$> x), rhs: foldMap (f . g) x, name: Fuse foldMap/<$>}
- warn: {lhs: foldMap f (x <&> g), rhs: foldMap (f . g) x, name: Fuse foldMap/<&>}
- warn: {lhs: foldMap f (fmap g x), rhs: foldMap (f . g) x, name: Fuse foldMap/fmap}
- warn: {lhs: foldMap f (map g x), rhs: foldMap (f . g) x, name: Fuse foldMap/map}
- warn: {lhs: traverse f (fmap g x), rhs: traverse (f . g) x, name: Fuse traverse/fmap}
- warn: {lhs: traverse f (g <$> x), rhs: traverse (f . g) x, name: Fuse traverse/<$>}
- warn: {lhs: traverse f (x <&> g), rhs: traverse (f . g) x, name: Fuse traverse/<&>}
- warn: {lhs: traverse_ f (fmap g x), rhs: traverse_ (f . g) x, name: Fuse traverse_/fmap}
- warn: {lhs: traverse_ f (g <$> x), rhs: traverse_ (f . g) x, name: Fuse traverse_/<$>}
- warn: {lhs: traverse_ f (x <&> g), rhs: traverse_ (f . g) x, name: Fuse traverse_/<&>}
# BY
- warn: {lhs: deleteBy (==), rhs: delete}
- warn: {lhs: groupBy (==), rhs: group}
- warn: {lhs: insertBy compare, rhs: insert}
- warn: {lhs: intersectBy (==), rhs: intersect}
- warn: {lhs: maximumBy compare, rhs: maximum}
- warn: {lhs: minimumBy compare, rhs: minimum}
- warn: {lhs: nubBy (==), rhs: nub}
- warn: {lhs: sortBy compare, rhs: sort}
- warn: {lhs: unionBy (==), rhs: union}
# FOLDS
- warn: {lhs: foldr (>>) (pure ()), rhs: sequence_}
- warn: {lhs: foldr (>>) (return ()), rhs: sequence_}
- warn: {lhs: foldr (&&) True, rhs: and}
- warn: {lhs: foldl (&&) True, rhs: and, note: IncreasesLaziness}
- warn: {lhs: foldr1 (&&) , rhs: and, note: "RemovesError on `[]`"}
- warn: {lhs: foldl1 (&&) , rhs: and, note: "RemovesError on `[]`"}
- warn: {lhs: foldr (||) False, rhs: or}
- warn: {lhs: foldl (||) False, rhs: or, note: IncreasesLaziness}
- warn: {lhs: foldr1 (||) , rhs: or, note: "RemovesError on `[]`"}
- warn: {lhs: foldl1 (||) , rhs: or, note: "RemovesError on `[]`"}
- warn: {lhs: foldl (+) 0, rhs: sum}
- warn: {lhs: foldr (+) 0, rhs: sum}
- warn: {lhs: foldl1 (+) , rhs: sum, note: "RemovesError on `[]`"}
- warn: {lhs: foldr1 (+) , rhs: sum, note: "RemovesError on `[]`"}
- warn: {lhs: foldl (*) 1, rhs: product}
- warn: {lhs: foldr (*) 1, rhs: product}
- warn: {lhs: foldl1 (*) , rhs: product, note: "RemovesError on `[]`"}
- warn: {lhs: foldr1 (*) , rhs: product, note: "RemovesError on `[]`"}
- warn: {lhs: foldl1 max , rhs: maximum}
- warn: {lhs: foldr1 max , rhs: maximum}
- warn: {lhs: foldl1 min , rhs: minimum}
- warn: {lhs: foldr1 min , rhs: minimum}
- warn: {lhs: foldr mplus mzero, rhs: msum}
# FUNCTION
- warn: {lhs: \x -> x, rhs: id}
- warn: {lhs: \x y -> x, rhs: const}
- warn: {lhs: curry fst, rhs: const}
- warn: {lhs: curry snd, rhs: \_ x -> x, note: "Alternatively, use const id"}
- warn: {lhs: flip const, rhs: \_ x -> x, note: "Alternatively, use const id"}
- warn: {lhs: "\\(x,y) -> y", rhs: snd}
- warn: {lhs: "\\(x,y) -> x", rhs: fst}
- hint: {lhs: "\\x y -> f (x,y)", rhs: curry f}
- hint: {lhs: "\\(x,y) -> f x y", rhs: uncurry f, note: IncreasesLaziness}
- warn: {lhs: f (fst p) (snd p), rhs: uncurry f p}
- warn: {lhs: "uncurry (\\x y -> z)", rhs: "\\(x,y) -> z"}
- warn: {lhs: "curry (\\(x,y) -> z)", rhs: "\\x y -> z"}
- warn: {lhs: uncurry (curry f), rhs: f}
- warn: {lhs: curry (uncurry f), rhs: f}
- warn: {lhs: "uncurry f (a, b)", rhs: f a b}
- warn: {lhs: ($) (f x), rhs: f x, name: Redundant $}
- warn: {lhs: (f $), rhs: f, name: Redundant $}
- warn: {lhs: (& f), rhs: f, name: Redundant &}
- hint: {lhs: \x -> y, rhs: const y, side: isAtom y && not (isWildcard y)}
# If any isWildcard recursively then x may be used but not mentioned explicitly
- warn: {lhs: flip f x y, rhs: f y x, side: isApp original && isAtom y}
- warn: {lhs: id x, rhs: x}
- warn: {lhs: id . x, rhs: x, name: Redundant id}
- warn: {lhs: x . id, rhs: x, name: Redundant id}
- warn: {lhs: "((,) x)", rhs: "(_noParen_ x,)", name: Use tuple-section, note: RequiresExtension TupleSections}
- warn: {lhs: "flip (,) x", rhs: "(,_noParen_ x)", name: Use tuple-section, note: RequiresExtension TupleSections}
- warn: {lhs: flip (flip f), rhs: f, note: DecreasesLaziness}
- warn: {lhs: flip f <*> g, rhs: f =<< g, name: Redundant flip}
- warn: {lhs: g <**> flip f, rhs: g >>= f, name: Redundant flip}
- warn: {lhs: flip f =<< g, rhs: f <*> g, name: Redundant flip}
- warn: {lhs: g >>= flip f, rhs: g Control.Applicative.<**> f, name: Redundant flip}
# CHAR
- warn: {lhs: "a >= 'a' && a <= 'z'", rhs: isAsciiLower a}
- warn: {lhs: "'a' <= a && a <= 'z'", rhs: isAsciiLower a}
- warn: {lhs: "a >= 'A' && a <= 'Z'", rhs: isAsciiUpper a}
- warn: {lhs: "'A' <= a && a <= 'Z'", rhs: isAsciiUpper a}
- warn: {lhs: "a >= '0' && a <= '9'", rhs: isDigit a}
- warn: {lhs: "'0' <= a && a <= '9'", rhs: isDigit a}
- warn: {lhs: "a >= '0' && a <= '7'", rhs: isOctDigit a}
- warn: {lhs: "'0' <= a && a <= '7'", rhs: isOctDigit a}
- warn: {lhs: isLower a || isUpper a, rhs: isAlpha a}
- warn: {lhs: isUpper a || isLower a, rhs: isAlpha a}
# BOOL
- warn: {lhs: x == True, rhs: x, name: Redundant ==}
- hint: {lhs: x == False, rhs: not x, name: Redundant ==}
- warn: {lhs: True == a, rhs: a, name: Redundant ==}
- hint: {lhs: False == a, rhs: not a, name: Redundant ==}
- hint: {lhs: (== True), rhs: id, name: Redundant ==}
- hint: {lhs: (== False), rhs: not, name: Redundant ==}
- hint: {lhs: (True ==), rhs: id, name: Redundant ==}
- hint: {lhs: (False ==), rhs: not, name: Redundant ==}
- warn: {lhs: a /= True, rhs: not a, name: Redundant /=}
- hint: {lhs: a /= False, rhs: a, name: Redundant /=}
- warn: {lhs: True /= a, rhs: not a, name: Redundant /=}
- hint: {lhs: False /= a, rhs: a, name: Redundant /=}
- hint: {lhs: (/= True), rhs: not, name: Redundant /=}
- hint: {lhs: (/= False), rhs: id, name: Redundant /=}
- hint: {lhs: (True /=), rhs: not, name: Redundant /=}
- hint: {lhs: (False /=), rhs: id, name: Redundant /=}
- warn: {lhs: if a then x else x, rhs: x, note: IncreasesLaziness, name: Redundant if}
- warn: {lhs: if a then True else False, rhs: a, name: Redundant if}
- warn: {lhs: if a then False else True, rhs: not a, name: Redundant if}
- warn: {lhs: if a then t else (if b then t else f), rhs: if a || b then t else f, name: Redundant if}
- warn: {lhs: if a then (if b then t else f) else f, rhs: if a && b then t else f, name: Redundant if}
- warn: {lhs: if x then True else y, rhs: x || y, side: notEq y False, name: Redundant if}
- warn: {lhs: if x then y else False, rhs: x && y, side: notEq y True, name: Redundant if}
- warn: {lhs: if | b -> t | otherwise -> f, rhs: if b then t else f, name: Redundant multi-way if}
- hint: {lhs: "case a of {True -> t; False -> f}", rhs: if a then t else f, name: Use if}
- hint: {lhs: "case a of {False -> f; True -> t}", rhs: if a then t else f, name: Use if}
- hint: {lhs: "case a of {True -> t; _ -> f}", rhs: if a then t else f, name: Use if}
- hint: {lhs: "case a of {False -> f; _ -> t}", rhs: if a then t else f, name: Use if}
- hint: {lhs: "if c then (True, x) else (False, x)", rhs: "(c, x)", note: IncreasesLaziness, name: Redundant if}
- hint: {lhs: "if c then (False, x) else (True, x)", rhs: "(not c, x)", note: IncreasesLaziness, name: Redundant if}
- hint: {lhs: "or [x, y]", rhs: x || y}
- hint: {lhs: "or [x, y, z]", rhs: x || y || z}
- hint: {lhs: "and [x, y]", rhs: x && y}
- hint: {lhs: "and [x, y, z]", rhs: x && y && z}
- warn: {lhs: if x then False else y, rhs: not x && y, side: notEq y True, name: Redundant if}
- warn: {lhs: if x then y else True, rhs: not x || y, side: notEq y False, name: Redundant if}
- warn: {lhs: not (not x), rhs: x, name: Redundant not}
# ARROW
- warn: {lhs: id *** g, rhs: second g}
- warn: {lhs: f *** id, rhs: first f}
- ignore: {lhs: zip (map f x) (map g x), rhs: map (f Control.Arrow.&&& g) x}
- ignore: {lhs: "\\x -> (f x, g x)", rhs: f Control.Arrow.&&& g}
- hint: {lhs: "(fst x, snd x)", rhs: x, note: DecreasesLaziness, name: Redundant pair}
# BIFUNCTOR
- warn: {lhs: bimap id g, rhs: second g}
- warn: {lhs: bimap f id, rhs: first f}
- warn: {lhs: first id, rhs: id}
- warn: {lhs: second id, rhs: id}
- warn: {lhs: bimap id id, rhs: id}
- warn: {lhs: first f (second g x), rhs: bimap f g x}
- warn: {lhs: second g (first f x), rhs: bimap f g x}
- warn: {lhs: first f (first g x), rhs: first (f . g) x}
- warn: {lhs: second f (second g x), rhs: second (f . g) x}
- warn: {lhs: bimap f h (bimap g i x), rhs: bimap (f . g) (h . i) x}
- warn: {lhs: first f (bimap g h x), rhs: bimap (f . g) h x}
- warn: {lhs: second g (bimap f h x), rhs: bimap f (g . h) x}
- warn: {lhs: bimap f h (first g x), rhs: bimap (f . g) h x}
- warn: {lhs: bimap f g (second h x), rhs: bimap f (g . h) x}
- hint: {lhs: "\\(x,y) -> (f x, g y)", rhs: Data.Bifunctor.bimap f g, note: IncreasesLaziness}
- hint: {lhs: "\\(x,y) -> (f x,y)", rhs: Data.Bifunctor.first f, note: IncreasesLaziness}
- hint: {lhs: "\\(x,y) -> (x,f y)", rhs: Data.Bifunctor.second f, note: IncreasesLaziness}
- hint: {lhs: "(f (fst x), g (snd x))", rhs: Data.Bifunctor.bimap f g x}
- hint: {lhs: "(f (fst x), snd x)", rhs: Data.Bifunctor.first f x}
- hint: {lhs: "(fst x, g (snd x))", rhs: Data.Bifunctor.second g x}
# FUNCTOR
- warn: {lhs: fmap f (fmap g x), rhs: fmap (f . g) x, name: Functor law}
- warn: {lhs: f <$> (g <$> x), rhs: f . g <$> x, name: Functor law}
- warn: {lhs: x <&> g <&> f, rhs: x <&> f . g, name: Functor law}
- warn: {lhs: fmap id, rhs: id, name: Functor law}
- warn: {lhs: id <$> x, rhs: x, name: Functor law}
- warn: {lhs: x <&> id, rhs: x, name: Functor law}
- warn: {lhs: f <$> g <$> x, rhs: f . g <$> x}
- hint: {lhs: fmap f $ x, rhs: f <$> x, side: isApp x || isAtom x}
- hint: {lhs: \x -> a <$> b x, rhs: fmap a . b}
- hint: {lhs: \x -> b x <&> a, rhs: fmap a . b}
- hint: {lhs: x *> pure y, rhs: x Data.Functor.$> y}
- hint: {lhs: x *> return y, rhs: x Data.Functor.$> y}
- hint: {lhs: pure x <* y, rhs: x Data.Functor.<$ y}
- hint: {lhs: return x <* y, rhs: x Data.Functor.<$ y}
- hint: {lhs: const x <$> y, rhs: x <$ y}
- hint: {lhs: pure x <$> y, rhs: x <$ y}
- hint: {lhs: return x <$> y, rhs: x <$ y}
- hint: {lhs: x <&> const y, rhs: x Data.Functor.$> y}
- hint: {lhs: x <&> pure y, rhs: x Data.Functor.$> y}
- hint: {lhs: x <&> return y, rhs: x Data.Functor.$> y}
- warn: {lhs: "fmap f (x,b)", rhs: "(x,f b)", name: Using fmap on tuple}
- warn: {lhs: "f <$> (x,b)", rhs: "(x,f b)", name: Using <$> on tuple}
- warn: {lhs: "(x,b) <&> f", rhs: "(x,f b)", name: Using <&> on tuple}
- warn: {lhs: "fmap f (x,y,b)", rhs: "(x,y,f b)", name: Using fmap on tuple}
- warn: {lhs: "f <$> (x,y,b)", rhs: "(x,y,f b)", name: Using <$> on tuple}
- warn: {lhs: "(x,y,b) <&> f", rhs: "(x,y,f b)", name: Using <&> on tuple}
# APPLICATIVE
- hint: {lhs: pure x <*> y, rhs: x <$> y}
- hint: {lhs: return x <*> y, rhs: x <$> y}
- warn: {lhs: x <* pure y, rhs: x}
- warn: {lhs: x <* return y, rhs: x}
- warn: {lhs: pure x *> y, rhs: "y"}
- warn: {lhs: return x *> y, rhs: "y"}
# MONAD
- warn: {lhs: pure a >>= f, rhs: f a, name: "Monad law, left identity"}
- warn: {lhs: return a >>= f, rhs: f a, name: "Monad law, left identity"}
- warn: {lhs: f =<< pure a, rhs: f a, name: "Monad law, left identity"}
- warn: {lhs: f =<< return a, rhs: f a, name: "Monad law, left identity"}
- warn: {lhs: m >>= pure, rhs: m, name: "Monad law, right identity"}
- warn: {lhs: m >>= return, rhs: m, name: "Monad law, right identity"}
- warn: {lhs: pure =<< m, rhs: m, name: "Monad law, right identity"}
- warn: {lhs: return =<< m, rhs: m, name: "Monad law, right identity"}
- warn: {lhs: liftM, rhs: fmap}
- warn: {lhs: liftA, rhs: fmap}
- hint: {lhs: m >>= pure . f, rhs: m Data.Functor.<&> f}
- hint: {lhs: m >>= return . f, rhs: m Data.Functor.<&> f}
- hint: {lhs: pure . f =<< m, rhs: f <$> m}
- hint: {lhs: return . f =<< m, rhs: f <$> m}
- warn: {lhs: fmap f x >>= g, rhs: x >>= g . f}
- warn: {lhs: f <$> x >>= g, rhs: x >>= g . f}
- warn: {lhs: x Data.Functor.<&> f >>= g, rhs: x >>= g . f}
- warn: {lhs: g =<< fmap f x, rhs: g . f =<< x}
- warn: {lhs: g =<< f <$> x, rhs: g . f =<< x}
- warn: {lhs: g =<< (x Data.Functor.<&> f), rhs: g . f =<< x}
- warn: {lhs: if x then y else pure (), rhs: Control.Monad.when x $ _noParen_ y, side: not (isAtom y)}
- warn: {lhs: if x then y else return (), rhs: Control.Monad.when x $ _noParen_ y, side: not (isAtom y)}
- warn: {lhs: if x then y else pure (), rhs: Control.Monad.when x y, side: isAtom y}
- warn: {lhs: if x then y else return (), rhs: Control.Monad.when x y, side: isAtom y}
- warn: {lhs: if x then pure () else y, rhs: Control.Monad.unless x $ _noParen_ y, side: isAtom y}
- warn: {lhs: if x then return () else y, rhs: Control.Monad.unless x $ _noParen_ y, side: isAtom y}
- warn: {lhs: if x then pure () else y, rhs: Control.Monad.unless x y, side: isAtom y}
- warn: {lhs: if x then return () else y, rhs: Control.Monad.unless x y, side: isAtom y}
- warn: {lhs: sequence (map f x), rhs: mapM f x}
- warn: {lhs: sequence_ (map f x), rhs: mapM_ f x}
- warn: {lhs: sequence (f <$> x), rhs: mapM f x}
- warn: {lhs: sequence (x <&> f), rhs: mapM f x}
- warn: {lhs: sequence (fmap f x), rhs: mapM f x}
- warn: {lhs: sequence_ (f <$> x), rhs: mapM_ f x}
- warn: {lhs: sequence_ (x <&> f), rhs: mapM_ f x}
- warn: {lhs: sequence_ (fmap f x), rhs: mapM_ f x}
- hint: {lhs: flip mapM, rhs: Control.Monad.forM}
- hint: {lhs: flip mapM_, rhs: Control.Monad.forM_}
- hint: {lhs: flip forM, rhs: mapM}
- hint: {lhs: flip forM_, rhs: mapM_}
- warn: {lhs: when (not x), rhs: unless x}
- warn: {lhs: when (notElem x y), rhs: unless (elem x y), name: Use unless}
- warn: {lhs: unless (not x), rhs: when x}
- warn: {lhs: unless (notElem x y), rhs: when (elem x y), name: Use when}
- warn: {lhs: x >>= id, rhs: Control.Monad.join x}
- warn: {lhs: id =<< x, rhs: Control.Monad.join x}
- hint: {lhs: join (f <$> x), rhs: f =<< x}
- hint: {lhs: join (x <&> f), rhs: f =<< x}
- hint: {lhs: join (fmap f x), rhs: f =<< x}
- hint: {lhs: a >> pure (), rhs: Control.Monad.void a, side: isAtom a || isApp a}
- hint: {lhs: a >> return (), rhs: Control.Monad.void a, side: isAtom a || isApp a}
- warn: {lhs: fmap (const ()), rhs: Control.Monad.void}
- warn: {lhs: const () <$> x, rhs: Control.Monad.void x}
- warn: {lhs: x <&> const (), rhs: Control.Monad.void x}
- warn: {lhs: () <$ x, rhs: Control.Monad.void x}
- warn: {lhs: flip (>=>), rhs: (<=<)}
- warn: {lhs: flip (<=<), rhs: (>=>)}
- warn: {lhs: flip (>>=), rhs: (=<<)}
- warn: {lhs: flip (=<<), rhs: (>>=)}
- hint: {lhs: \x -> f x >>= g, rhs: f Control.Monad.>=> g}
- hint: {lhs: \x -> f =<< g x, rhs: f Control.Monad.<=< g}
- hint: {lhs: (>>= f) . g, rhs: f Control.Monad.<=< g}
- hint: {lhs: (f =<<) . g, rhs: f Control.Monad.<=< g}
- warn: {lhs: a >> forever a, rhs: forever a}
- hint: {lhs: liftM2 id, rhs: ap}
- warn: {lhs: liftM2 f (pure x), rhs: fmap (f x)}
- warn: {lhs: liftA2 f (return x), rhs: fmap (f x)}
- warn: {lhs: liftM2 f (pure x), rhs: fmap (f x)}
- warn: {lhs: liftM2 f (return x), rhs: fmap (f x)}
- warn: {lhs: fmap f (pure x), rhs: pure (f x)}
- warn: {lhs: fmap f (return x), rhs: return (f x)}
- warn: {lhs: f <$> pure x, rhs: pure (f x)}
- warn: {lhs: pure x <&> f, rhs: pure (f x)}
- warn: {lhs: f <$> return x, rhs: return (f x)}
- warn: {lhs: return x <&> f, rhs: return (f x)}
- warn: {lhs: mapM (uncurry f) (zip l m), rhs: zipWithM f l m}
- warn: {lhs: mapM_ (void . f), rhs: mapM_ f}
- warn: {lhs: forM_ x (void . f), rhs: forM_ x f}
- warn: {lhs: a >>= \_ -> b, rhs: a >> b}
- warn: {lhs: m <* pure x, rhs: m}
- warn: {lhs: m <* return x, rhs: m}
- warn: {lhs: pure x *> m, rhs: m}
- warn: {lhs: return x *> m, rhs: m}
- warn: {lhs: pure x >> m, rhs: m}
- warn: {lhs: return x >> m, rhs: m}
- warn: {lhs: "forM [1..n] (const f)", rhs: replicateM n f}
- warn: {lhs: "for [1..n] (const f)", rhs: replicateM n f}
- warn: {lhs: "forM [1..n] (\\_ -> x)", rhs: replicateM n x}
- warn: {lhs: "for [1..n] (\\_ -> x)", rhs: replicateM n x}
# STATE MONAD
- warn: {lhs: fst (runState x y), rhs: evalState x y}
- warn: {lhs: snd (runState x y), rhs: execState x y}
# MONAD LIST
- warn: {lhs: unzip <$> mapM f x, rhs: Control.Monad.mapAndUnzipM f x}
- warn: {lhs: mapM f x <&> unzip, rhs: Control.Monad.mapAndUnzipM f x}
- warn: {lhs: fmap unzip (mapM f x), rhs: Control.Monad.mapAndUnzipM f x}
- warn: {lhs: sequence (zipWith f x y), rhs: Control.Monad.zipWithM f x y}
- warn: {lhs: sequence_ (zipWith f x y), rhs: Control.Monad.zipWithM_ f x y}
- warn: {lhs: sequence (replicate n x), rhs: Control.Monad.replicateM n x}
- warn: {lhs: sequence_ (replicate n x), rhs: Control.Monad.replicateM_ n x}
- warn: {lhs: sequenceA (zipWith f x y), rhs: Control.Monad.zipWithM f x y}
- warn: {lhs: sequenceA_ (zipWith f x y), rhs: Control.Monad.zipWithM_ f x y}
- warn: {lhs: sequenceA (replicate n x), rhs: Control.Monad.replicateM n x}
- warn: {lhs: sequenceA_ (replicate n x), rhs: Control.Monad.replicateM_ n x}
- warn: {lhs: mapM f (replicate n x), rhs: Control.Monad.replicateM n (f x)}
- warn: {lhs: mapM_ f (replicate n x), rhs: Control.Monad.replicateM_ n (f x)}
- warn: {lhs: mapM f (map g x), rhs: mapM (f . g) x, name: Fuse mapM/map}
- warn: {lhs: mapM_ f (map g x), rhs: mapM_ (f . g) x, name: Fuse mapM_/map}
- warn: {lhs: traverse f (map g x), rhs: traverse (f . g) x, name: Fuse traverse/map}
- warn: {lhs: traverse_ f (map g x), rhs: traverse_ (f . g) x, name: Fuse traverse_/map}
- warn: {lhs: mapM id, rhs: sequence}
- warn: {lhs: mapM_ id, rhs: sequence_}
# APPLICATIVE / TRAVERSABLE
- warn: {lhs: flip traverse, rhs: for}
- warn: {lhs: flip for, rhs: traverse}
- warn: {lhs: flip traverse_, rhs: for_}
- warn: {lhs: flip for_, rhs: traverse_}
- warn: {lhs: foldr (*>) (pure ()), rhs: sequenceA_}
- warn: {lhs: foldr (*>) (return ()), rhs: sequence_}
- warn: {lhs: foldr (<|>) empty, rhs: asum}
- warn: {lhs: liftA2 (flip ($)), rhs: (<**>)}
- warn: {lhs: liftA2 f (pure x), rhs: fmap (f x)}
- warn: {lhs: liftA2 f (return x), rhs: fmap (f x)}
- warn: {lhs: Just <$> a <|> pure Nothing, rhs: optional a}
- warn: {lhs: Just <$> a <|> return Nothing, rhs: optional a}
- warn: {lhs: empty <|> x, rhs: x, name: "Alternative law, left identity"}
- warn: {lhs: x <|> empty, rhs: x, name: "Alternative law, right identity"}
- warn: {lhs: traverse id, rhs: sequenceA}
- warn: {lhs: traverse_ id, rhs: sequenceA_}
# LIST COMP
- hint: {lhs: "if b then [x] else []", rhs: "[x | b]", name: Use list comprehension}
- hint: {lhs: "if b then [] else [x]", rhs: "[x | not b]", name: Use list comprehension}
- hint: {lhs: "[x | x <- y]", rhs: "y", side: isVar x, name: Redundant list comprehension}
- hint: {lhs: "[ f x | x <- [y] ]", rhs: "[f y]", side: isVar x, name: Redundant list comprehension}
# SEQ
- warn: {lhs: seq x x, rhs: x, name: Redundant seq}
- warn: {lhs: join seq, rhs: id, name: Redundant seq}
- warn: {lhs: id $! x, rhs: x, name: Redundant $!}
- warn: {lhs: seq x y, rhs: "y", side: isWHNF x, name: Redundant seq}
- warn: {lhs: f $! x, rhs: f x, side: isWHNF x, name: Redundant $!}
- warn: {lhs: evaluate x, rhs: return x, side: isWHNF x, name: Redundant evaluate}
- warn: {lhs: seq (rnf x) (), rhs: rnf x, name: Redundant seq}
# TUPLE
- warn: {lhs: fst (unzip x), rhs: map fst x}
- warn: {lhs: snd (unzip x), rhs: map snd x}
- hint: {lhs: "\\x y -> (x, y)", rhs: "(,)"}
- hint: {lhs: "\\x y z -> (x, y, z)", rhs: "(,,)"}
- hint: {lhs: "(,b) a", rhs: "(a,b)", side: isAtom a, name: Evaluate}
- hint: {lhs: "(a,) b", rhs: "(a,b)", side: isAtom b, name: Evaluate}
- warn: {lhs: "Data.List.NonEmpty.unzip", rhs: "Data.Functor.unzip", name: "Avoid NonEmpty.unzip", note: "The function is being deprecated"}
# MAYBE
- warn: {lhs: maybe x id, rhs: Data.Maybe.fromMaybe x}
- warn: {lhs: maybe Nothing Just, rhs: id, name: Redundant maybe}
- warn: {lhs: maybe False (const True), rhs: Data.Maybe.isJust}
- warn: {lhs: maybe True (const False), rhs: Data.Maybe.isNothing}
- warn: {lhs: maybe False (x ==), rhs: (Just x ==)}
- warn: {lhs: maybe True (x /=), rhs: (Just x /=)}
- warn: {lhs: maybe False (== x), rhs: (Just x ==), note: ValidInstance Eq x}
- warn: {lhs: maybe True (/= x), rhs: (Just x /=), note: ValidInstance Eq x}
# The following two hints seem to be somewhat unwelcome, e.g.
# https://github.com/ndmitchell/hlint/issues/1177
- ignore: {lhs: fromMaybe False x, rhs: Just True == x} # Eta expanded, see https://github.com/ndmitchell/hlint/issues/970#issuecomment-643645053
- ignore: {lhs: fromMaybe True x, rhs: Just False /= x}
- warn: {lhs: not (isNothing x), rhs: isJust x}
- warn: {lhs: not (isJust x), rhs: isNothing x}
- warn: {lhs: "maybe [] (:[])", rhs: maybeToList}
- warn: {lhs: catMaybes (map f x), rhs: mapMaybe f x}
- warn: {lhs: catMaybes (f <$> x), rhs: mapMaybe f x}
- warn: {lhs: catMaybes (x <&> f), rhs: mapMaybe f x}
- warn: {lhs: catMaybes (fmap f x), rhs: mapMaybe f x}
- hint: {lhs: case x of Nothing -> y; Just a -> a , rhs: Data.Maybe.fromMaybe y x, side: isAtom y, name: Replace case with fromMaybe}
- hint: {lhs: case x of Just a -> a; Nothing -> y, rhs: Data.Maybe.fromMaybe y x, side: isAtom y, name: Replace case with fromMaybe}
- hint: {lhs: case x of Nothing -> y; Just a -> f a , rhs: maybe y f x, side: isAtom y && isAtom f, name: Replace case with maybe}
- hint: {lhs: case x of Just a -> f a; Nothing -> y, rhs: maybe y f x, side: isAtom y && isAtom f, name: Replace case with maybe}
- warn: {lhs: if isNothing x then y else f (fromJust x), rhs: maybe y f x}
- warn: {lhs: if isJust x then f (fromJust x) else y, rhs: maybe y f x}
- warn: {lhs: maybe Nothing (Just . f), rhs: fmap f}
- hint: {lhs: map fromJust (filter isJust x), rhs: Data.Maybe.catMaybes x}
- hint: {lhs: filter isJust (map f x), rhs: map Just (mapMaybe f x), name: Use mapMaybe}
- hint: {lhs: filter isJust (f <*> x), rhs: map Just (mapMaybe f x), name: Use mapMaybe}
- hint: {lhs: filter isJust (x <&> f), rhs: map Just (mapMaybe f x), name: Use mapMaybe}
- hint: {lhs: filter isJust (fmap f x), rhs: map Just (mapMaybe f x), name: Use mapMaybe}
- warn: {lhs: x == Nothing , rhs: isNothing x}
- warn: {lhs: Nothing == x , rhs: isNothing x}
- warn: {lhs: x /= Nothing , rhs: Data.Maybe.isJust x}
- warn: {lhs: Nothing /= x , rhs: Data.Maybe.isJust x}
- warn: {lhs: concatMap (maybeToList . f), rhs: Data.Maybe.mapMaybe f}
- warn: {lhs: concatMap maybeToList, rhs: catMaybes}
- warn: {lhs: maybe n Just x, rhs: x Control.Applicative.<|> n}
- warn: {lhs: if isNothing x then y else fromJust x, rhs: fromMaybe y x}
- warn: {lhs: if isJust x then fromJust x else y, rhs: fromMaybe y x}
- warn: {lhs: isJust x && (fromJust x == y), rhs: x == Just y}
- warn: {lhs: isJust y && (x == fromJust y), rhs: Just x == y}
- warn: {lhs: mapMaybe f (map g x), rhs: mapMaybe (f . g) x, name: Fuse mapMaybe/map}
- warn: {lhs: fromMaybe a (fmap f x), rhs: maybe a f x}
- warn: {lhs: fromMaybe a (f <$> x), rhs: maybe a f x}
- warn: {lhs: fromMaybe a (x <&> f), rhs: maybe a f x}
- warn: {lhs: mapMaybe id, rhs: catMaybes}
- hint: {lhs: "[x | Just x <- a]", rhs: Data.Maybe.catMaybes a, side: isVar x}
- hint: {lhs: case m of Nothing -> Nothing; Just x -> x, rhs: Control.Monad.join m}
- hint: {lhs: maybe Nothing id, rhs: join}
- hint: {lhs: maybe Nothing f x, rhs: f =<< x}
- warn: {lhs: maybe x f (g <$> y), rhs: maybe x (f . g) y, name: Redundant <$>}
- warn: {lhs: maybe x f (y <&> g), rhs: maybe x (f . g) y, name: Redundant <&>}
- warn: {lhs: maybe x f (fmap g y), rhs: maybe x (f . g) y, name: Redundant fmap}
- warn: {lhs: isJust (f <$> x), rhs: isJust x}
- warn: {lhs: isJust (x <&> f), rhs: isJust x}
- warn: {lhs: isJust (fmap f x), rhs: isJust x}
- warn: {lhs: isNothing (f <$> x), rhs: isNothing x}
- warn: {lhs: isNothing (x <&> f), rhs: isNothing x}
- warn: {lhs: isNothing (fmap f x), rhs: isNothing x}
- warn: {lhs: fromJust (f <$> x), rhs: f (fromJust x), note: IncreasesLaziness}
- warn: {lhs: fromJust (x <&> f), rhs: f (fromJust x), note: IncreasesLaziness}
- warn: {lhs: fromJust (fmap f x), rhs: f (fromJust x), note: IncreasesLaziness}
- warn: {lhs: mapMaybe f (g <$> x), rhs: mapMaybe (f . g) x, name: Redundant <$>}
- warn: {lhs: mapMaybe f (x <&> g), rhs: mapMaybe (f . g) x, name: Redundant <&>}
- warn: {lhs: mapMaybe f (fmap g x), rhs: mapMaybe (f . g) x, name: Redundant fmap}
- warn: {lhs: catMaybes (nub x), rhs: nub (catMaybes x), name: Move nub out}
- warn: {lhs: lefts (nub x), rhs: nub (lefts x), name: Move nub out}
- warn: {lhs: rights (nub x), rhs: nub (rights x), name: Move nub out}
- warn: {lhs: catMaybes (reverse x), rhs: reverse (catMaybes x), name: Move reverse out}
- warn: {lhs: lefts (reverse x), rhs: reverse (lefts x), name: Move reverse out}
- warn: {lhs: rights (reverse x), rhs: reverse (rights x), name: Move reverse out}
- warn: {lhs: catMaybes (sort x), rhs: sort (catMaybes x), name: Move sort out}
- warn: {lhs: lefts (sort x), rhs: sort (lefts x), name: Move sort out}
- warn: {lhs: rights (sort x), rhs: sort (rights x), name: Move sort out}
- warn: {lhs: catMaybes (nubOrd x), rhs: nubOrd (catMaybes x), name: Move nubOrd out}
- warn: {lhs: lefts (nubOrd x), rhs: nubOrd (lefts x), name: Move nubOrd out}
- warn: {lhs: rights (nubOrd x), rhs: nubOrd (rights x), name: Move nubOrd out}
- warn: {lhs: filter f (reverse x), rhs: reverse (filter f x), name: Move reverse out}
# EITHER
- warn: {lhs: "[a | Left a <- b]", rhs: lefts b, side: isVar a}
- warn: {lhs: "[a | Right a <- b]", rhs: rights b, side: isVar a}
- warn: {lhs: either Left (Right . f), rhs: fmap f}
- warn: {lhs: either f g (fmap h x), rhs: either f (g . h) x, name: Redundant fmap}
- warn: {lhs: either f g (h <$> x), rhs: either f (g . h) x, name: Redundant <$>}
- warn: {lhs: either f g (x <&> h), rhs: either f (g . h) x, name: Redundant <&>}
- warn: {lhs: isLeft (fmap f x), rhs: isLeft x}
- warn: {lhs: isLeft (f <$> x), rhs: isLeft x}
- warn: {lhs: isLeft (x <&> f), rhs: isLeft x}
- warn: {lhs: isRight (fmap f x), rhs: isRight x}
- warn: {lhs: isRight (f <$> x), rhs: isRight x}
- warn: {lhs: isRight (x <&> f), rhs: isRight x}
- warn: {lhs: fromLeft x (fmap f y), rhs: fromLeft x y}
- warn: {lhs: fromLeft x (f <$> y), rhs: fromLeft x y}
- warn: {lhs: fromLeft x (y <&> f), rhs: fromLeft x y}
- warn: {lhs: fromRight x (fmap f y), rhs: either (const x) f y}
- warn: {lhs: fromRight x (f <$> y), rhs: either (const x) f y}
- warn: {lhs: fromRight x (y <&> f), rhs: either (const x) f y}
- warn: {lhs: either (const x) id, rhs: fromRight x}
- warn: {lhs: either id (const x), rhs: fromLeft x}
- warn: {lhs: either Left f x, rhs: f =<< x}
# INFIX
- hint: {lhs: elem x y, rhs: x `elem` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: notElem x y, rhs: x `notElem` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: isInfixOf x y, rhs: x `isInfixOf` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: isSuffixOf x y, rhs: x `isSuffixOf` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: isPrefixOf x y, rhs: x `isPrefixOf` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: union x y, rhs: x `union` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
- hint: {lhs: intersect x y, rhs: x `intersect` y, side: not (isInfixApp original) && not (isParen result), name: Use infix}
# MATHS
- warn: {lhs: fromIntegral x, rhs: x, side: isLitInt x, name: Redundant fromIntegral}
- warn: {lhs: fromInteger x, rhs: x, side: isLitInt x, name: Redundant fromInteger}
- hint: {lhs: x + negate y, rhs: x - y}
- hint: {lhs: 0 - x, rhs: negate x}
- warn: {lhs: negate (negate x), rhs: x, name: Redundant negate}
- hint: {lhs: log y / log x, rhs: logBase x y}
- hint: {lhs: sin x / cos x, rhs: tan x}
- hint: {lhs: rem n 2 == 0, rhs: even n}
- hint: {lhs: 0 == rem n 2, rhs: even n}
- hint: {lhs: rem n 2 /= 0, rhs: odd n}
- hint: {lhs: 0 /= rem n 2, rhs: odd n}
- hint: {lhs: mod n 2 == 0, rhs: even n}
- hint: {lhs: 0 == mod n 2, rhs: even n}
- hint: {lhs: mod n 2 /= 0, rhs: odd n}
- hint: {lhs: 0 /= mod n 2, rhs: odd n}
- hint: {lhs: not (even x), rhs: odd x}
- hint: {lhs: not (odd x), rhs: even x}
- hint: {lhs: x ** 0.5, rhs: sqrt x}
- hint: {lhs: x ^ 0, rhs: "1", name: Use 1}
- hint: {lhs: round (x - 0.5), rhs: floor x}
# CONCURRENT
- hint: {lhs: mapM_ (writeChan a), rhs: writeList2Chan a}
- warn: {lhs: atomically (readTVar x), rhs: readTVarIO x}
- warn: {lhs: atomically (newTVar x), rhs: newTVarIO x}
- warn: {lhs: atomically (newTMVar x), rhs: newTMVarIO x}
- warn: {lhs: atomically newEmptyTMVar, rhs: newEmptyTMVarIO}
# TYPEABLE
- hint: {lhs: "typeOf (a :: b)", rhs: "typeRep (Proxy :: Proxy b)"}
# EXCEPTION
- hint: {lhs: flip Control.Exception.catch, rhs: handle}
- hint: {lhs: flip handle, rhs: Control.Exception.catch}
- hint: {lhs: flip (catchJust p), rhs: handleJust p}
- hint: {lhs: flip (handleJust p), rhs: catchJust p}
- hint: {lhs: Control.Exception.bracket b (const a) (const t), rhs: Control.Exception.bracket_ b a t}
- hint: {lhs: Control.Exception.bracket (openFile x y) hClose, rhs: withFile x y}
- hint: {lhs: Control.Exception.bracket (openBinaryFile x y) hClose, rhs: withBinaryFile x y}
- hint: {lhs: throw (ErrorCall a), rhs: error a}
- warn: {lhs: toException NonTermination, rhs: nonTermination}
- warn: {lhs: toException NestedAtomically, rhs: nestedAtomically}
# IOREF
- hint: {lhs: modifyIORef r (const x), rhs: writeIORef r x}
- hint: {lhs: modifyIORef r (\v -> x), rhs: writeIORef r x}
# STOREABLE/PTR
- hint: {lhs: castPtr nullPtr, rhs: nullPtr}
- hint: {lhs: castPtr (castPtr x), rhs: castPtr x}
- hint: {lhs: plusPtr (castPtr x), rhs: plusPtr x}
- hint: {lhs: minusPtr (castPtr x), rhs: minusPtr x}
- hint: {lhs: minusPtr x (castPtr y), rhs: minusPtr x y}
- hint: {lhs: peekByteOff (castPtr x), rhs: peekByteOff x}
- hint: {lhs: pokeByteOff (castPtr x), rhs: pokeByteOff x}
# WEAK POINTERS
- warn: {lhs: mkWeak a a b, rhs: mkWeakPtr a b}
- warn: {lhs: "mkWeak a (a, b) c", rhs: mkWeakPair a b c}
# FOLDABLE
- warn: {lhs: case m of Nothing -> pure (); Just x -> f x, rhs: Data.Foldable.for_ m f}
- warn: {lhs: case m of Nothing -> return (); Just x -> f x, rhs: Data.Foldable.forM_ m f}
- warn: {lhs: case m of Just x -> f x; Nothing -> pure (), rhs: Data.Foldable.for_ m f}
- warn: {lhs: case m of Just x -> f x; Nothing -> return (), rhs: Data.Foldable.forM_ m f}
- warn: {lhs: case m of Just x -> f x; _ -> pure (), rhs: Data.Foldable.for_ m f}
- warn: {lhs: case m of Just x -> f x; _ -> return (), rhs: Data.Foldable.forM_ m f}
- warn: {lhs: when (isJust m) (f (fromJust m)), rhs: Data.Foldable.for_ m f}
- hint: {lhs: concatMap f (fmap g x), rhs: concatMap (f . g) x, name: Fuse concatMap/fmap}
- hint: {lhs: concatMap f (g <$> x), rhs: concatMap (f . g) x, name: Fuse concatMap/<$>}
- hint: {lhs: concatMap f (x <&> g), rhs: concatMap (f . g) x, name: Fuse concatMap/<&>}
- warn: {lhs: null (concatMap f x), rhs: all (null . f) x}
- warn: {lhs: or (concat x), rhs: any or x}
- warn: {lhs: or (concatMap f x), rhs: any (or . f) x}
- warn: {lhs: and (concat x), rhs: all and x}
- warn: {lhs: and (concatMap f x), rhs: all (and . f) x}
- warn: {lhs: any f (concat x), rhs: any (any f) x}
- warn: {lhs: any f (concatMap g x), rhs: any (any f . g) x}
- warn: {lhs: all f (concat x), rhs: all (all f) x}
- warn: {lhs: all f (concatMap g x), rhs: all (all f . g) x}
- warn: {lhs: fold (concatMap f x), rhs: foldMap (fold . f) x}
- warn: {lhs: foldMap f (concatMap g x), rhs: foldMap (foldMap f . g) x}
- warn: {lhs: catMaybes (concatMap f x), rhs: concatMap (catMaybes . f) x, name: Move catMaybes}
- warn: {lhs: catMaybes (concat x), rhs: concatMap catMaybes x, name: Move catMaybes}
- hint: {lhs: filter f (concatMap g x), rhs: concatMap (filter f . g) x, name: Move filter}
- hint: {lhs: filter f (concat x), rhs: concatMap (filter f) x, name: Move filter}
- warn: {lhs: mapMaybe f (concatMap g x), rhs: concatMap (mapMaybe f . g) x, name: Move mapMaybe}
- warn: {lhs: mapMaybe f (concat x), rhs: concatMap (mapMaybe f) x, name: Move mapMaybe}
- warn: {lhs: or (fmap p x), rhs: any p x}
- warn: {lhs: or (p <$> x), rhs: any p x}
- warn: {lhs: or (x <&> p), rhs: any p x}
- warn: {lhs: and (fmap p x), rhs: all p x}
- warn: {lhs: and (p <$> x), rhs: all p x}
- warn: {lhs: and (x <&> p), rhs: all p x}
- warn: {lhs: any f (fmap g x), rhs: any (f . g) x}
- warn: {lhs: any f (g <$> x), rhs: any (f . g) x}
- warn: {lhs: any f (x <&> g), rhs: any (f . g) x}
- warn: {lhs: all f (fmap g x), rhs: all (f . g) x}
- warn: {lhs: all f (g <$> x), rhs: all (f . g) x}
- warn: {lhs: all f (x <&> g), rhs: all (f . g) x}
- hint: {lhs: foldr f z (fmap g x), rhs: foldr (f . g) z x, name: Fuse foldr/fmap}
- hint: {lhs: foldr f z (g <$> x), rhs: foldr (f . g) z x, name: Fuse foldr/<$>}
- hint: {lhs: foldr f z (x <&> g), rhs: foldr (f . g) z x, name: Fuse foldr/<&>}
# STATE MONAD
- warn: {lhs: f <$> Control.Monad.State.get, rhs: gets f}
- warn: {lhs: Control.Monad.State.get <&> f, rhs: gets f}
- warn: {lhs: fmap f Control.Monad.State.get, rhs: gets f}
- warn: {lhs: f <$> Control.Monad.State.gets g, rhs: gets (f . g)}
- warn: {lhs: Control.Monad.State.gets g <&> f, rhs: gets (f . g)}
- warn: {lhs: fmap f (Control.Monad.State.gets g), rhs: gets (f . g)}
- warn: {lhs: f <$> Control.Monad.Reader.ask, rhs: asks f}
- warn: {lhs: Control.Monad.Reader.ask <&> f, rhs: asks f}
- warn: {lhs: fmap f Control.Monad.Reader.ask, rhs: asks f}
- warn: {lhs: f <$> Control.Monad.Reader.asks g, rhs: asks (f . g)}
- warn: {lhs: Control.Monad.Reader.asks g <&> f, rhs: asks (f . g)}
- warn: {lhs: fmap f (Control.Monad.Reader.asks g), rhs: asks (f . g)}
- warn: {lhs: fst (runState m s), rhs: evalState m s}
- warn: {lhs: snd (runState m s), rhs: execState m s}
# EVALUATE
- warn: {lhs: True && x, rhs: x, name: Evaluate}
- warn: {lhs: False && x, rhs: "False", name: Evaluate}
- warn: {lhs: True || x, rhs: "True", name: Evaluate}
- warn: {lhs: False || x, rhs: x, name: Evaluate}
- warn: {lhs: not True, rhs: "False", name: Evaluate}
- warn: {lhs: not False, rhs: "True", name: Evaluate}
- warn: {lhs: Nothing >>= k, rhs: Nothing, name: Evaluate}
- warn: {lhs: k =<< Nothing, rhs: Nothing, name: Evaluate}
- warn: {lhs: either f g (Left x), rhs: f x, name: Evaluate}
- warn: {lhs: either f g (Right y), rhs: g y, name: Evaluate}
- warn: {lhs: "fst (x,y)", rhs: x, name: Evaluate}
- warn: {lhs: "snd (x,y)", rhs: "y", name: Evaluate}
- warn: {lhs: fromJust (Just x), rhs: x, name: Evaluate}
- warn: {lhs: fromLeft y (Left x), rhs: x, name: Evaluate}
- warn: {lhs: fromLeft y (Right x), rhs: "y", name: Evaluate}
- warn: {lhs: fromRight y (Right x), rhs: x, name: Evaluate}
- warn: {lhs: fromRight y (Left x), rhs: "y", name: Evaluate}
- warn: {lhs: "head [x]", rhs: "x", name: Evaluate}
- warn: {lhs: "last [x]", rhs: "x", name: Evaluate}
- warn: {lhs: "tail [x]", rhs: "[]", name: Evaluate}
- warn: {lhs: "init [x]", rhs: "[]", name: Evaluate}
- warn: {lhs: "null [x]", rhs: "False", name: Evaluate}
- warn: {lhs: "null []", rhs: "True", name: Evaluate}
- warn: {lhs: "null \"\"", rhs: "True", name: Evaluate}
- warn: {lhs: "length []", rhs: "0", name: Evaluate}
- warn: {lhs: "length \"\"", rhs: "0", name: Evaluate}
- warn: {lhs: "foldl f z []", rhs: z, name: Evaluate}
- warn: {lhs: "foldr f z []", rhs: z, name: Evaluate}
- warn: {lhs: "foldr1 f [x]", rhs: x, name: Evaluate}
- warn: {lhs: "scanr f z []", rhs: "[z]", name: Evaluate}
- warn: {lhs: "scanr1 f []", rhs: "[]", name: Evaluate}
- warn: {lhs: "scanr1 f [x]", rhs: "[x]", name: Evaluate}
- warn: {lhs: "take n []", rhs: "[]", note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: "take n \"\"", rhs: "\"\"", note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: "drop n []", rhs: "[]", note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: "drop n \"\"", rhs: "\"\"", note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: "takeWhile p []", rhs: "[]", name: Evaluate}
- warn: {lhs: "takeWhile p \"\"", rhs: "\"\"", name: Evaluate}
- warn: {lhs: "dropWhile p []", rhs: "[]", name: Evaluate}
- warn: {lhs: "dropWhile p \"\"", rhs: "\"\"", name: Evaluate}
- warn: {lhs: "span p []", rhs: "([],[])", name: Evaluate}
- warn: {lhs: "span p \"\"", rhs: "(\"\",\"\")", name: Evaluate}
- warn: {lhs: "lines \"\"", rhs: "[]", name: Evaluate}
- warn: {lhs: "lines []", rhs: "[]", name: Evaluate}
- warn: {lhs: "unwords []", rhs: "\"\"", name: Evaluate}
- warn: {lhs: x - 0, rhs: x, name: Evaluate}
- warn: {lhs: x * 1, rhs: x, name: Evaluate}
- warn: {lhs: x / 1, rhs: x, name: Evaluate}
- warn: {lhs: "concat [a]", rhs: a, name: Evaluate}
- warn: {lhs: "concat []", rhs: "[]", name: Evaluate}
- warn: {lhs: "concatMap f [a]", rhs: f a, name: Evaluate}
- warn: {lhs: "concatMap f []", rhs: "[]", name: Evaluate}
- warn: {lhs: "zip [] []", rhs: "[]", name: Evaluate}
- warn: {lhs: const x y, rhs: x, name: Evaluate}
- warn: {lhs: any (const False), rhs: const False, note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: all (const True), rhs: const True, note: IncreasesLaziness, name: Evaluate}
- warn: {lhs: "[] ++ x", rhs: x, name: Evaluate}
- warn: {lhs: "\"\" ++ x", rhs: x, name: Evaluate}
- warn: {lhs: "x ++ []", rhs: x, name: Evaluate}
- warn: {lhs: "x ++ \"\"", rhs: x, name: Evaluate}
- warn: {lhs: "all f [a]", rhs: f a, name: Evaluate}
- warn: {lhs: "all f []", rhs: "True", name: Evaluate}
- warn: {lhs: "any f [a]", rhs: f a, name: Evaluate}
- warn: {lhs: "any f []", rhs: "False", name: Evaluate}
- warn: {lhs: "maximum [a]", rhs: a, name: Evaluate}
- warn: {lhs: "minimum [a]", rhs: a, name: Evaluate}
- warn: {lhs: "map f []", rhs: "[]", name: Evaluate}
- warn: {lhs: "map f [a]", rhs: "[f a]", name: Evaluate}
# FOLDABLE + TUPLES
- warn: {lhs: "foldr f z (x,b)", rhs: f b z, name: Using foldr on tuple}
- warn: {lhs: "foldr' f z (x,b)", rhs: f b z, name: Using foldr' on tuple}
- warn: {lhs: "foldl f z (x,b)", rhs: f z b, name: Using foldl on tuple}
- warn: {lhs: "foldl' f z (x,b)", rhs: f z b, name: Using foldl' on tuple}
- warn: {lhs: "foldMap f (x,b)", rhs: f b, name: Using foldMap on tuple}