1{-# LANGUAGE ViewPatterns, ScopedTypeVariables #-}
2{-# LANGUAGE FlexibleContexts #-}
3{-# LANGUAGE TypeFamilies #-}
4{-
5
6Raise an error if you are bracketing an atom, or are enclosed by a
7list bracket.
8
9<TEST>
10-- expression bracket reduction
11yes = (f x) x -- @Suggestion f x x
12no = f (x x)
13yes = (foo) -- foo
14yes = (foo bar) -- @Suggestion foo bar
15yes = foo (bar) -- @Warning bar
16yes = foo ((x x)) -- @Suggestion (x x)
17yes = (f x) ||| y -- @Suggestion f x ||| y
18yes = if (f x) then y else z -- @Suggestion if f x then y else z
19yes = if x then (f y) else z -- @Suggestion if x then f y else z
20yes = (a foo) :: Int -- @Suggestion a foo :: Int
21yes = [(foo bar)] -- @Suggestion [foo bar]
22yes = foo ((x y), z) -- @Suggestion (x y, z)
23yes = C { f = (e h) } -- @Suggestion C {f = e h}
24yes = \ x -> (x && x) -- @Suggestion \x -> x && x
25no = \(x -> y) -> z
26yes = (`foo` (bar baz)) -- @Suggestion (`foo` bar baz)
27yes = f ((x)) -- @Warning x
28main = do f; (print x) -- @Suggestion do f print x
29yes = f (x) y -- @Warning x
30no = f (+x) y
31no = f ($x) y
32no = ($x)
33yes = (($x))
34no = ($1)
35yes = (($1)) -- @Warning ($1)
36no = (+5)
37yes = ((+5)) -- @Warning (+5)
38issue909 = case 0 of { _ | n <- (0 :: Int) -> n }
39issue909 = foo (\((x :: z) -> y) -> 9 + x * 7)
40issue909 = foo (\((x : z) -> y) -> 9 + x * 7) -- \(x : z -> y) -> 9 + x * 7
41issue909 = let ((x:: y) -> z) = q in q
42issue909 = do {((x :: y) -> z) <- e; return 1}
43issue970 = (f x +) (g x) -- f x + (g x)
44issue969 = (Just \x -> x || x) *> Just True
45
46-- type bracket reduction
47foo :: (Int -> Int) -> Int
48foo :: (Maybe Int) -> a -- @Suggestion Maybe Int -> a
49instance Named (DeclHead S)
50data Foo = Foo {foo :: (Maybe Foo)} -- @Suggestion foo :: Maybe Foo
51
52-- pattern bracket reduction
53foo (x:xs) = 1
54foo (True) = 1 -- @Warning True
55foo ((True)) = 1 -- @Warning True
56foo (A{}) = True -- A{}
57f x = case x of (Nothing) -> 1; _ -> 2 -- Nothing
58
59-- dollar reduction tests
60no = groupFsts . sortFst $ mr
61yes = split "to" $ names -- split "to" names
62yes = white $ keysymbol -- white keysymbol
63yes = operator foo $ operator -- operator foo operator
64no = operator foo $ operator bar
65yes = return $ Record{a=b}
66no = f $ [1,2..5] -- f [1,2..5]
67
68-- $/bracket rotation tests
69yes = (b $ c d) ++ e -- b (c d) ++ e
70yes = (a b $ c d) ++ e -- a b (c d) ++ e
71no = (f . g $ a) ++ e
72no = quickCheck ((\h -> cySucc h == succ h) :: Hygiene -> Bool)
73foo = (case x of y -> z; q -> w) :: Int
74
75-- backup fixity resolution
76main = do a += b . c; return $ a . b
77
78-- <$> bracket tests
79yes = (foo . bar x) <$> baz q -- foo . bar x <$> baz q
80no = foo . bar x <$> baz q
81
82-- annotations
83main = 1; {-# ANN module ("HLint: ignore Use camelCase" :: String) #-}
84main = 1; {-# ANN module (1 + (2)) #-} -- 2
85
86-- special case from esqueleto, see #224
87main = operate <$> (select $ from $ \user -> return $ user ^. UserEmail)
88-- unknown fixity, see #426
89bad x = x . (x +? x . x)
90-- special case people don't like to warn on
91special = foo $ f{x=1}
92special = foo $ Rec{x=1}
93special = foo (f{x=1})
94loadCradleOnlyonce = skipManyTill anyMessage (message @PublishDiagnosticsNotification)
95
96-- type splices are a bit special
97no = f @($x)
98</TEST>
99-}
100
101
102module Hint.Bracket(bracketHint) where
103
104import Hint.Type(DeclHint,Idea(..),rawIdea,warn,suggest,Severity(..),toRefactSrcSpan,toSS)
105import Data.Data
106import Data.List.Extra
107import Data.Generics.Uniplate.DataOnly
108import Refact.Types
109
110import GHC.Hs
111import Outputable
112import SrcLoc
113import GHC.Util
114import Language.Haskell.GhclibParserEx.GHC.Hs.Expr
115import Language.Haskell.GhclibParserEx.GHC.Utils.Outputable
116
117bracketHint :: DeclHint
118bracketHint _ _ x =
119  concatMap (\x -> bracket prettyExpr isPartialAtom True x ++ dollar x) (childrenBi (descendBi annotations x) :: [LHsExpr GhcPs]) ++
120  concatMap (bracket unsafePrettyPrint (const False) False) (childrenBi x :: [LHsType GhcPs]) ++
121  concatMap (bracket unsafePrettyPrint (const False) False) (childrenBi x :: [LPat GhcPs]) ++
122  concatMap fieldDecl (childrenBi x)
123   where
124     -- Brackets the roots of annotations are fine, so we strip them.
125     annotations :: AnnDecl GhcPs -> AnnDecl GhcPs
126     annotations= descendBi $ \x -> case (x :: LHsExpr GhcPs) of
127       L _ (HsPar _ x) -> x
128       x -> x
129
130-- If we find ourselves in the context of a section and we want to
131-- issue a warning that a child therein has unneccessary brackets,
132-- we'd rather report 'Found : (`Foo` (Bar Baz))' rather than 'Found :
133-- `Foo` (Bar Baz)'. If left to 'unsafePrettyPrint' we'd get the
134-- latter (in contrast to the HSE pretty printer). This patches things
135-- up.
136prettyExpr :: LHsExpr GhcPs -> String
137prettyExpr s@(L _ SectionL{}) = unsafePrettyPrint (noLoc (HsPar noExtField s) :: LHsExpr GhcPs)
138prettyExpr s@(L _ SectionR{}) = unsafePrettyPrint (noLoc (HsPar noExtField s) :: LHsExpr GhcPs)
139prettyExpr x = unsafePrettyPrint x
140
141-- 'Just _' if at least one set of parens were removed. 'Nothing' if
142-- zero parens were removed.
143remParens' :: Brackets a => a -> Maybe a
144remParens' = fmap go . remParen
145  where
146    go e = maybe e go (remParen e)
147
148isPartialAtom :: LHsExpr GhcPs -> Bool
149-- Might be '$x', which was really '$ x', but TH enabled misparsed it.
150isPartialAtom (L _ (HsSpliceE _ (HsTypedSplice _ HasDollar _ _) )) = True
151isPartialAtom (L _ (HsSpliceE _ (HsUntypedSplice _ HasDollar _ _) )) = True
152isPartialAtom x = isRecConstr x || isRecUpdate x
153
154bracket :: forall a . (Data a, HasSrcSpan a, Outputable a, Brackets a) => (a -> String) -> (a -> Bool) -> Bool -> a -> [Idea]
155bracket pretty isPartialAtom root = f Nothing
156  where
157    msg = "Redundant bracket"
158    -- 'f' is a (generic) function over types in 'Brackets
159    -- (expressions, patterns and types). Arguments are, 'f (Maybe
160    -- (index, parent, gen)) child'.
161    f :: (HasSrcSpan a, Data a, Outputable a, Brackets a) => Maybe (Int, a , a -> a) -> a -> [Idea]
162    -- No context. Removing parentheses from 'x' succeeds?
163    f Nothing o@(remParens' -> Just x)
164      -- If at the root, or 'x' is an atom, 'x' parens are redundant.
165      | root || isAtom x
166      , not $ isPartialAtom x =
167          (if isAtom x then bracketError else bracketWarning) msg o x : g x
168    -- In some context, removing parentheses from 'x' succeeds and 'x'
169    -- is atomic?
170    f Just{} o@(remParens' -> Just x)
171      | isAtom x
172      , not $ isPartialAtom x =
173          bracketError msg o x : g x
174    -- In some context, removing parentheses from 'x' succeeds. Does
175    -- 'x' actually need bracketing in this context?
176    f (Just (i, o, gen)) v@(remParens' -> Just x)
177      | not $ needBracket i o x, not $ isPartialAtom x =
178          rawIdea Suggestion msg (getLoc v) (pretty o) (Just (pretty (gen x))) [] [r] : g x
179      where
180        typ = findType v
181        r = Replace typ (toSS v) [("x", toSS x)] "x"
182    -- Regardless of the context, there are no parentheses to remove
183    -- from 'x'.
184    f _ x = g x
185
186    g :: (HasSrcSpan a, Data a, Outputable a, Brackets a) => a -> [Idea]
187    -- Enumerate over all the immediate children of 'o' looking for
188    -- redundant parentheses in each.
189    g o = concat [f (Just (i, o, gen)) x | (i, (x, gen)) <- zipFrom 0 $ holes o]
190
191bracketWarning :: (HasSrcSpan a, HasSrcSpan b, Outputable a, Outputable b, Brackets b)  => String -> a -> b -> Idea
192bracketWarning msg o x =
193  suggest msg o x [Replace (findType x) (toSS o) [("x", toSS x)] "x"]
194
195bracketError :: (HasSrcSpan a, HasSrcSpan b, Outputable a, Outputable b, Brackets b) => String -> a -> b -> Idea
196bracketError msg o x =
197  warn msg o x [Replace (findType x) (toSS o) [("x", toSS x)] "x"]
198
199fieldDecl ::  LConDeclField GhcPs -> [Idea]
200fieldDecl o@(L loc f@ConDeclField{cd_fld_type=v@(L l (HsParTy _ c))}) =
201   let r = L loc (f{cd_fld_type=c}) :: LConDeclField GhcPs in
202   [rawIdea Suggestion "Redundant bracket" l
203    (showSDocUnsafe $ ppr_fld o) -- Note this custom printer!
204    (Just (showSDocUnsafe $ ppr_fld r))
205    []
206    [Replace Type (toSS v) [("x", toSS c)] "x"]]
207   where
208     -- If we call 'unsafePrettyPrint' on a field decl, we won't like
209     -- the output (e.g. "[foo, bar] :: T"). Here we use a custom
210     -- printer to work around (snarfed from
211     -- https://hackage.haskell.org/package/ghc-lib-parser-8.8.1/docs/src/HsTypes.html#pprConDeclFields).
212     ppr_fld (L _ ConDeclField { cd_fld_names = ns, cd_fld_type = ty, cd_fld_doc = doc })
213       = ppr_names ns <+> dcolon <+> ppr ty <+> ppr_mbDoc doc
214     ppr_fld (L _ (XConDeclField x)) = ppr x
215
216     ppr_names [n] = ppr n
217     ppr_names ns = sep (punctuate comma (map ppr ns))
218fieldDecl _ = []
219
220-- This function relies heavily on fixities having been applied to the
221-- raw parse tree.
222dollar :: LHsExpr GhcPs -> [Idea]
223dollar = concatMap f . universe
224  where
225    f x = [ (suggest "Redundant $" x y [r]){ideaSpan = getLoc d} | L _ (OpApp _ a d b) <- [x], isDol d
226            , let y = noLoc (HsApp noExtField a b) :: LHsExpr GhcPs
227            , not $ needBracket 0 y a
228            , not $ needBracket 1 y b
229            , not $ isPartialAtom b
230            , let r = Replace Expr (toSS x) [("a", toSS a), ("b", toSS b)] "a b"]
231          ++
232          [ suggest "Move brackets to avoid $" x (t y) [r]
233            |(t, e@(L _ (HsPar _ (L _ (OpApp _ a1 op1 a2))))) <- splitInfix x
234            , isDol op1
235            , isVar a1 || isApp a1 || isPar a1, not $ isAtom a2
236            , varToStr a1 /= "select" -- special case for esqueleto, see #224
237            , let y = noLoc $ HsApp noExtField a1 (noLoc (HsPar noExtField a2))
238            , let r = Replace Expr (toSS e) [("a", toSS a1), ("b", toSS a2)] "a (b)" ]
239          ++  -- Special case of (v1 . v2) <$> v3
240          [ (suggest "Redundant bracket" x y [r]){ideaSpan = locPar}
241          | L _ (OpApp _ (L locPar (HsPar _ o1@(L locNoPar (OpApp _ _ (isDot -> True) _)))) o2 v3) <- [x], varToStr o2 == "<$>"
242          , let y = noLoc (OpApp noExtField o1 o2 v3) :: LHsExpr GhcPs
243          , let r = Replace Expr (toRefactSrcSpan locPar) [("a", toRefactSrcSpan locNoPar)] "a"]
244          ++
245          [ suggest "Redundant section" x y [r]
246          | L _ (HsApp _ (L _ (HsPar _ (L _ (SectionL _ a b)))) c) <- [x]
247          -- , error $ show (unsafePrettyPrint a, gshow b, unsafePrettyPrint c)
248          , let y = noLoc $ OpApp noExtField a b c :: LHsExpr GhcPs
249          , let r = Replace Expr (toSS x) [("x", toSS a), ("op", toSS b), ("y", toSS c)] "x op y"]
250
251splitInfix :: LHsExpr GhcPs -> [(LHsExpr GhcPs -> LHsExpr GhcPs, LHsExpr GhcPs)]
252splitInfix (L l (OpApp _ lhs op rhs)) =
253  [(L l . OpApp noExtField lhs op, rhs), (\lhs -> L l (OpApp noExtField lhs op rhs), lhs)]
254splitInfix _ = []
255