Pretty-print an empty list of fundeps without '|' (should fix #1260)
[ghc.git] / libraries / template-haskell / Language / Haskell / TH / Ppr.hs
1 -- TH.Ppr contains a prettyprinter for the
2 -- Template Haskell datatypes
3
4 module Language.Haskell.TH.Ppr where
5 -- All of the exports from this module should
6 -- be "public" functions. The main module TH
7 -- re-exports them all.
8
9 import Text.PrettyPrint.HughesPJ (render)
10 import Language.Haskell.TH.PprLib
11 import Language.Haskell.TH.Syntax
12 import Data.Char ( toLower )
13
14 nestDepth :: Int
15 nestDepth = 4
16
17 type Precedence = Int
18 appPrec, opPrec, noPrec :: Precedence
19 appPrec = 2 -- Argument of a function application
20 opPrec = 1 -- Argument of an infix operator
21 noPrec = 0 -- Others
22
23 parensIf :: Bool -> Doc -> Doc
24 parensIf True d = parens d
25 parensIf False d = d
26
27 ------------------------------
28
29 pprint :: Ppr a => a -> String
30 pprint x = render $ to_HPJ_Doc $ ppr x
31
32 class Ppr a where
33 ppr :: a -> Doc
34 ppr_list :: [a] -> Doc
35 ppr_list = vcat . map ppr
36
37 instance Ppr a => Ppr [a] where
38 ppr x = ppr_list x
39
40 ------------------------------
41 instance Ppr Name where
42 ppr v = pprName True v -- text (show v)
43
44 ------------------------------
45 instance Ppr Info where
46 ppr (ClassI d) = ppr d
47 ppr (TyConI d) = ppr d
48 ppr (PrimTyConI name arity is_unlifted)
49 = text "Primitive"
50 <+> (if is_unlifted then text "unlifted" else empty)
51 <+> text "type construtor" <+> quotes (ppr name)
52 <+> parens (text "arity" <+> int arity)
53 ppr (ClassOpI v ty cls fix)
54 = text "Class op from" <+> ppr cls <> colon <+>
55 vcat [ppr_sig v ty, pprFixity v fix]
56 ppr (DataConI v ty tc fix)
57 = text "Constructor from" <+> ppr tc <> colon <+>
58 vcat [ppr_sig v ty, pprFixity v fix]
59 ppr (TyVarI v ty)
60 = text "Type variable" <+> ppr v <+> equals <+> ppr ty
61 ppr (VarI v ty mb_d fix)
62 = vcat [ppr_sig v ty, pprFixity v fix,
63 case mb_d of { Nothing -> empty; Just d -> ppr d }]
64
65 ppr_sig v ty = ppr v <+> text "::" <+> ppr ty
66
67 pprFixity :: Name -> Fixity -> Doc
68 pprFixity v f | f == defaultFixity = empty
69 pprFixity v (Fixity i d) = ppr_fix d <+> int i <+> ppr v
70 where ppr_fix InfixR = text "infixr"
71 ppr_fix InfixL = text "infixl"
72 ppr_fix InfixN = text "infix"
73
74
75 ------------------------------
76 instance Ppr Exp where
77 ppr = pprExp noPrec
78
79 pprInfixExp :: Exp -> Doc
80 pprInfixExp (VarE v) = pprName False v
81 pprInfixExp (ConE v) = pprName False v
82 pprInfixExp _ = error "Attempt to pretty-print non-variable or constructor in infix context!"
83
84 pprExp :: Precedence -> Exp -> Doc
85 pprExp _ (VarE v) = ppr v
86 pprExp _ (ConE c) = ppr c
87 pprExp i (LitE l) = pprLit i l
88 pprExp i (AppE e1 e2) = parensIf (i >= appPrec) $ pprExp opPrec e1
89 <+> pprExp appPrec e2
90 pprExp i (InfixE (Just e1) op (Just e2))
91 = parensIf (i >= opPrec) $ pprExp opPrec e1
92 <+> pprInfixExp op
93 <+> pprExp opPrec e2
94 pprExp _ (InfixE me1 op me2) = parens $ pprMaybeExp noPrec me1
95 <+> pprInfixExp op
96 <+> pprMaybeExp noPrec me2
97 pprExp i (LamE ps e) = parensIf (i > noPrec) $ char '\\' <> hsep (map (pprPat appPrec) ps)
98 <+> text "->" <+> ppr e
99 pprExp _ (TupE es) = parens $ sep $ punctuate comma $ map ppr es
100 -- Nesting in Cond is to avoid potential problems in do statments
101 pprExp i (CondE guard true false)
102 = parensIf (i > noPrec) $ sep [text "if" <+> ppr guard,
103 nest 1 $ text "then" <+> ppr true,
104 nest 1 $ text "else" <+> ppr false]
105 pprExp i (LetE ds e) = parensIf (i > noPrec) $ text "let" <+> ppr ds
106 $$ text " in" <+> ppr e
107 pprExp i (CaseE e ms)
108 = parensIf (i > noPrec) $ text "case" <+> ppr e <+> text "of"
109 $$ nest nestDepth (ppr ms)
110 pprExp i (DoE ss) = parensIf (i > noPrec) $ text "do" <+> ppr ss
111 pprExp _ (CompE []) = error "Can't happen: pprExp (CompExp [])"
112 -- This will probably break with fixity declarations - would need a ';'
113 pprExp _ (CompE ss) = text "[" <> ppr s
114 <+> text "|"
115 <+> (sep $ punctuate comma $ map ppr ss')
116 <> text "]"
117 where s = last ss
118 ss' = init ss
119 pprExp _ (ArithSeqE d) = ppr d
120 pprExp _ (ListE es) = brackets $ sep $ punctuate comma $ map ppr es
121 pprExp i (SigE e t) = parensIf (i > noPrec) $ ppr e <+> text "::" <+> ppr t
122 pprExp _ (RecConE nm fs) = ppr nm <> braces (pprFields fs)
123 pprExp _ (RecUpdE e fs) = pprExp appPrec e <> braces (pprFields fs)
124
125 pprFields :: [(Name,Exp)] -> Doc
126 pprFields = sep . punctuate comma . map (\(s,e) -> ppr s <+> equals <+> ppr e)
127
128 pprMaybeExp :: Precedence -> Maybe Exp -> Doc
129 pprMaybeExp _ Nothing = empty
130 pprMaybeExp i (Just e) = pprExp i e
131
132 ------------------------------
133 instance Ppr Stmt where
134 ppr (BindS p e) = ppr p <+> text "<-" <+> ppr e
135 ppr (LetS ds) = text "let" <+> ppr ds
136 ppr (NoBindS e) = ppr e
137 ppr (ParS sss) = sep $ punctuate (text "|")
138 $ map (sep . punctuate comma . map ppr) sss
139
140 ------------------------------
141 instance Ppr Match where
142 ppr (Match p rhs ds) = ppr p <+> pprBody False rhs
143 $$ where_clause ds
144
145 ------------------------------
146 pprBody :: Bool -> Body -> Doc
147 pprBody eq (GuardedB xs) = nest nestDepth $ vcat $ map do_guard xs
148 where eqd = if eq then text "=" else text "->"
149 do_guard (NormalG g, e) = text "|" <+> ppr g <+> eqd <+> ppr e
150 do_guard (PatG ss, e) = text "|" <+> vcat (map ppr ss)
151 $$ nest nestDepth (eqd <+> ppr e)
152 pprBody eq (NormalB e) = (if eq then text "=" else text "->") <+> ppr e
153
154 ------------------------------
155 pprLit :: Precedence -> Lit -> Doc
156 pprLit i (IntPrimL x) = parensIf (i > noPrec && x < 0)
157 (integer x <> char '#')
158 pprLit i (FloatPrimL x) = parensIf (i > noPrec && x < 0)
159 (float (fromRational x) <> char '#')
160 pprLit i (DoublePrimL x) = parensIf (i > noPrec && x < 0)
161 (double (fromRational x) <> text "##")
162 pprLit i (IntegerL x) = parensIf (i > noPrec && x < 0) (integer x)
163 pprLit _ (CharL c) = text (show c)
164 pprLit _ (StringL s) = text (show s)
165 pprLit i (RationalL rat) = parensIf (i > noPrec) $ rational rat
166
167 ------------------------------
168 instance Ppr Pat where
169 ppr = pprPat noPrec
170
171 pprPat :: Precedence -> Pat -> Doc
172 pprPat i (LitP l) = pprLit i l
173 pprPat _ (VarP v) = ppr v
174 pprPat _ (TupP ps) = parens $ sep $ punctuate comma $ map ppr ps
175 pprPat i (ConP s ps) = parensIf (i > noPrec) $ ppr s
176 <+> sep (map (pprPat appPrec) ps)
177 pprPat i (InfixP p1 n p2)
178 = parensIf (i > noPrec)
179 $ pprPat opPrec p1 <+> pprName False n <+> pprPat opPrec p2
180 pprPat i (TildeP p) = parensIf (i > noPrec) $ char '~' <> pprPat appPrec p
181 pprPat i (AsP v p) = parensIf (i > noPrec) $ ppr v <> text "@"
182 <> pprPat appPrec p
183 pprPat _ WildP = text "_"
184 pprPat _ (RecP nm fs)
185 = parens $ ppr nm
186 <+> braces (sep $ punctuate comma $
187 map (\(s,p) -> ppr s <+> equals <+> ppr p) fs)
188 pprPat _ (ListP ps) = brackets $ sep $ punctuate comma $ map ppr ps
189 pprPat i (SigP p t) = parensIf (i > noPrec) $ ppr p <+> text "::" <+> ppr t
190
191 ------------------------------
192 instance Ppr Dec where
193 ppr (FunD f cs) = vcat $ map (\c -> ppr f <+> ppr c) cs
194 ppr (ValD p r ds) = ppr p <+> pprBody True r
195 $$ where_clause ds
196 ppr (TySynD t xs rhs) = text "type" <+> ppr t <+> hsep (map ppr xs)
197 <+> text "=" <+> ppr rhs
198 ppr (DataD ctxt t xs cs decs)
199 = text "data"
200 <+> pprCxt ctxt
201 <+> ppr t <+> hsep (map ppr xs)
202 <+> sep (pref $ map ppr cs)
203 $$ if null decs
204 then empty
205 else nest nestDepth
206 $ text "deriving"
207 <+> parens (hsep $ punctuate comma $ map ppr decs)
208 where pref :: [Doc] -> [Doc]
209 pref [] = [char '='] -- Can't happen in H98
210 pref (d:ds) = (char '=' <+> d):map (char '|' <+>) ds
211 ppr (NewtypeD ctxt t xs c decs)
212 = text "newtype"
213 <+> pprCxt ctxt
214 <+> ppr t <+> hsep (map ppr xs)
215 <+> char '=' <+> ppr c
216 $$ if null decs
217 then empty
218 else nest nestDepth
219 $ text "deriving"
220 <+> parens (hsep $ punctuate comma $ map ppr decs)
221 ppr (ClassD ctxt c xs fds ds) = text "class" <+> pprCxt ctxt
222 <+> ppr c <+> hsep (map ppr xs) <+> ppr fds
223 $$ where_clause ds
224 ppr (InstanceD ctxt i ds) = text "instance" <+> pprCxt ctxt <+> ppr i
225 $$ where_clause ds
226 ppr (SigD f t) = ppr f <+> text "::" <+> ppr t
227 ppr (ForeignD f) = ppr f
228
229 ------------------------------
230 instance Ppr FunDep where
231 ppr (FunDep xs ys) = hsep (map ppr xs) <+> text "->" <+> hsep (map ppr ys)
232 ppr_list [] = empty
233 ppr_list xs = char '|' <+> sep (punctuate (text ", ") (map ppr xs))
234
235 ------------------------------
236 instance Ppr Foreign where
237 ppr (ImportF callconv safety impent as typ)
238 = text "foreign import"
239 <+> showtextl callconv
240 <+> showtextl safety
241 <+> text (show impent)
242 <+> ppr as
243 <+> text "::" <+> ppr typ
244 ppr (ExportF callconv expent as typ)
245 = text "foreign export"
246 <+> showtextl callconv
247 <+> text (show expent)
248 <+> ppr as
249 <+> text "::" <+> ppr typ
250
251 ------------------------------
252 instance Ppr Clause where
253 ppr (Clause ps rhs ds) = hsep (map (pprPat appPrec) ps) <+> pprBody True rhs
254 $$ where_clause ds
255
256 ------------------------------
257 instance Ppr Con where
258 ppr (NormalC c sts) = ppr c <+> sep (map pprStrictType sts)
259 ppr (RecC c vsts)
260 = ppr c <+> braces (sep (punctuate comma $ map pprVarStrictType vsts))
261 ppr (InfixC st1 c st2) = pprStrictType st1 <+> pprName False c <+> pprStrictType st2
262 ppr (ForallC ns ctxt con) = text "forall" <+> hsep (map ppr ns)
263 <+> char '.' <+> pprCxt ctxt <+> ppr con
264
265 ------------------------------
266 pprVarStrictType :: (Name, Strict, Type) -> Doc
267 -- Slight infelicity: with print non-atomic type with parens
268 pprVarStrictType (v, str, t) = ppr v <+> text "::" <+> pprStrictType (str, t)
269
270 ------------------------------
271 pprStrictType :: (Strict, Type) -> Doc
272 -- Prints with parens if not already atomic
273 pprStrictType (IsStrict, t) = char '!' <> pprParendType t
274 pprStrictType (NotStrict, t) = pprParendType t
275
276 ------------------------------
277 pprParendType :: Type -> Doc
278 pprParendType (VarT v) = ppr v
279 pprParendType (ConT c) = ppr c
280 pprParendType (TupleT 0) = text "()"
281 pprParendType (TupleT n) = parens (hcat (replicate (n-1) comma))
282 pprParendType ArrowT = parens (text "->")
283 pprParendType ListT = text "[]"
284 pprParendType other = parens (ppr other)
285
286 instance Ppr Type where
287 ppr (ForallT tvars ctxt ty) =
288 text "forall" <+> hsep (map ppr tvars) <+> text "."
289 <+> pprCxt ctxt <+> ppr ty
290 ppr ty = pprTyApp (split ty)
291
292 pprTyApp :: (Type, [Type]) -> Doc
293 pprTyApp (ArrowT, [arg1,arg2]) = sep [ppr arg1 <+> text "->", ppr arg2]
294 pprTyApp (ListT, [arg]) = brackets (ppr arg)
295 pprTyApp (TupleT n, args)
296 | length args == n = parens (sep (punctuate comma (map ppr args)))
297 pprTyApp (fun, args) = pprParendType fun <+> sep (map pprParendType args)
298
299 split :: Type -> (Type, [Type]) -- Split into function and args
300 split t = go t []
301 where go (AppT t1 t2) args = go t1 (t2:args)
302 go ty args = (ty, args)
303
304 ------------------------------
305 pprCxt :: Cxt -> Doc
306 pprCxt [] = empty
307 pprCxt [t] = ppr t <+> text "=>"
308 pprCxt ts = parens (hsep $ punctuate comma $ map ppr ts) <+> text "=>"
309
310 ------------------------------
311 instance Ppr Range where
312 ppr = brackets . pprRange
313 where pprRange :: Range -> Doc
314 pprRange (FromR e) = ppr e <> text ".."
315 pprRange (FromThenR e1 e2) = ppr e1 <> text ","
316 <> ppr e2 <> text ".."
317 pprRange (FromToR e1 e2) = ppr e1 <> text ".." <> ppr e2
318 pprRange (FromThenToR e1 e2 e3) = ppr e1 <> text ","
319 <> ppr e2 <> text ".."
320 <> ppr e3
321
322 ------------------------------
323 where_clause :: [Dec] -> Doc
324 where_clause [] = empty
325 where_clause ds = nest nestDepth $ text "where" <+> vcat (map ppr ds)
326
327 showtextl :: Show a => a -> Doc
328 showtextl = text . map toLower . show
329