2 % (c) The University of Glasgow, 1992-2006
5 Here we collect a variety of helper functions that construct or
6 analyse HsSyn. All these functions deal with generic HsSyn; functions
7 which deal with the intantiated versions are located elsewhere:
9 Parameterised by Module
10 ---------------- -------------
11 RdrName parser/RdrHsSyn
17 -- The above warning supression flag is a temporary kludge.
18 -- While working on this module you are encouraged to remove it and fix
19 -- any warnings in the module. See
20 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
25 #include "HsVersions.h"
47 %************************************************************************
49 Some useful helpers for constructing syntax
51 %************************************************************************
53 These functions attempt to construct a not-completely-useless SrcSpan
54 from their components, compared with the nl* functions below which
55 just attach noSrcSpan to everything.
58 mkHsPar :: LHsExpr id -> LHsExpr id
59 mkHsPar e = L (getLoc e) (HsPar e)
61 mkSimpleMatch :: [LPat id] -> LHsExpr id -> LMatch id
62 mkSimpleMatch pats rhs
64 Match pats Nothing (unguardedGRHSs rhs)
68 (pat:_) -> combineSrcSpans (getLoc pat) (getLoc rhs)
70 unguardedGRHSs :: LHsExpr id -> GRHSs id
71 unguardedGRHSs rhs = GRHSs (unguardedRHS rhs) emptyLocalBinds
73 unguardedRHS :: LHsExpr id -> [LGRHS id]
74 unguardedRHS rhs@(L loc _) = [L loc (GRHS [] rhs)]
76 mkHsAppTy :: LHsType name -> LHsType name -> LHsType name
77 mkHsAppTy t1 t2 = addCLoc t1 t2 (HsAppTy t1 t2)
79 mkHsApp :: LHsExpr name -> LHsExpr name -> LHsExpr name
80 mkHsApp e1 e2 = addCLoc e1 e2 (HsApp e1 e2)
82 nlHsTyApp :: name -> [Type] -> LHsExpr name
83 nlHsTyApp fun_id tys = noLoc (HsWrap (mkWpTyApps tys) (HsVar fun_id))
85 mkLHsWrap :: HsWrapper -> LHsExpr id -> LHsExpr id
86 mkLHsWrap co_fn (L loc e) = L loc (mkHsWrap co_fn e)
88 mkHsWrap :: HsWrapper -> HsExpr id -> HsExpr id
89 mkHsWrap co_fn e | isIdHsWrapper co_fn = e
90 | otherwise = HsWrap co_fn e
92 mkHsLam :: [LPat id] -> LHsExpr id -> LHsExpr id
93 mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
95 matches = mkMatchGroup [mkSimpleMatch pats body]
97 mkMatchGroup :: [LMatch id] -> MatchGroup id
98 mkMatchGroup matches = MatchGroup matches placeHolderType
100 mkHsDictLet :: LHsBinds Id -> LHsExpr Id -> LHsExpr Id
101 -- Used for the dictionary bindings gotten from TcSimplify
102 -- We make them recursive to be on the safe side
103 mkHsDictLet binds expr
104 | isEmptyLHsBinds binds = expr
105 | otherwise = L (getLoc expr) (HsLet (HsValBinds val_binds) expr)
107 val_binds = ValBindsOut [(Recursive, binds)] []
109 mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
110 -- Used for constructing dictionary terms etc, so no locations
111 mkHsConApp data_con tys args
112 = foldl mk_app (nlHsTyApp (dataConWrapId data_con) tys) args
114 mk_app f a = noLoc (HsApp f (noLoc a))
116 mkSimpleHsAlt :: LPat id -> LHsExpr id -> LMatch id
117 -- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
118 mkSimpleHsAlt pat expr
119 = mkSimpleMatch [pat] expr
121 -------------------------------
122 -- These are the bits of syntax that contain rebindable names
123 -- See RnEnv.lookupSyntaxName
125 mkHsIntegral i = HsIntegral i noSyntaxExpr
126 mkHsFractional f = HsFractional f noSyntaxExpr
127 mkHsIsString s = HsIsString s noSyntaxExpr
128 mkHsDo ctxt stmts body = HsDo ctxt stmts body placeHolderType
130 mkNPat lit neg = NPat lit neg noSyntaxExpr placeHolderType
131 mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr
133 mkExprStmt expr = ExprStmt expr noSyntaxExpr placeHolderType
134 mkBindStmt pat expr = BindStmt pat expr noSyntaxExpr noSyntaxExpr
135 mkRecStmt stmts = RecStmt stmts [] [] [] emptyLHsBinds
137 -------------------------------
138 --- A useful function for building @OpApps@. The operator is always a
139 -- variable, and we don't know the fixity yet.
140 mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2
142 mkHsSplice e = HsSplice unqualSplice e
144 unqualSplice = mkRdrUnqual (mkVarOccFS FSLIT("splice"))
145 -- A name (uniquified later) to
146 -- identify the splice
148 mkHsString s = HsString (mkFastString s)
151 userHsTyVarBndrs :: [Located name] -> [Located (HsTyVarBndr name)]
152 userHsTyVarBndrs bndrs = [ L loc (UserTyVar v) | L loc v <- bndrs ]
156 %************************************************************************
158 Constructing syntax with no location info
160 %************************************************************************
163 nlHsVar :: id -> LHsExpr id
164 nlHsVar n = noLoc (HsVar n)
166 nlHsLit :: HsLit -> LHsExpr id
167 nlHsLit n = noLoc (HsLit n)
169 nlVarPat :: id -> LPat id
170 nlVarPat n = noLoc (VarPat n)
172 nlLitPat :: HsLit -> LPat id
173 nlLitPat l = noLoc (LitPat l)
175 nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
176 nlHsApp f x = noLoc (HsApp f x)
178 nlHsIntLit n = noLoc (HsLit (HsInt n))
180 nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
181 nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
183 nlHsVarApps :: id -> [id] -> LHsExpr id
184 nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
186 mk f a = HsApp (noLoc f) (noLoc a)
188 nlConVarPat :: id -> [id] -> LPat id
189 nlConVarPat con vars = nlConPat con (map nlVarPat vars)
191 nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
192 nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))
194 nlConPat :: id -> [LPat id] -> LPat id
195 nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))
197 nlNullaryConPat :: id -> LPat id
198 nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))
200 nlWildConPat :: DataCon -> LPat RdrName
201 nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
202 (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))
204 nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)
205 nlWildPat = noLoc (WildPat placeHolderType) -- Pre-typechecking
207 nlHsDo :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> LHsExpr id
208 nlHsDo ctxt stmts body = noLoc (mkHsDo ctxt stmts body)
210 nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)
212 nlHsLam match = noLoc (HsLam (mkMatchGroup [match]))
213 nlHsPar e = noLoc (HsPar e)
214 nlHsIf cond true false = noLoc (HsIf cond true false)
215 nlHsCase expr matches = noLoc (HsCase expr (mkMatchGroup matches))
216 nlTuple exprs box = noLoc (ExplicitTuple exprs box)
217 nlList exprs = noLoc (ExplicitList placeHolderType exprs)
219 nlHsAppTy f t = noLoc (HsAppTy f t)
220 nlHsTyVar x = noLoc (HsTyVar x)
221 nlHsFunTy a b = noLoc (HsFunTy a b)
223 nlHsTyConApp tycon tys = foldl nlHsAppTy (nlHsTyVar tycon) tys
228 %************************************************************************
230 Bindings; with a location at the top
232 %************************************************************************
235 mkFunBind :: Located id -> [LMatch id] -> HsBind id
236 -- Not infix, with place holders for coercion and free vars
237 mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False, fun_matches = mkMatchGroup ms,
238 fun_co_fn = idHsWrapper, bind_fvs = placeHolderNames,
242 mkVarBind :: SrcSpan -> RdrName -> LHsExpr RdrName -> LHsBind RdrName
243 mkVarBind loc var rhs = mk_easy_FunBind loc var [] rhs
246 mk_easy_FunBind :: SrcSpan -> RdrName -> [LPat RdrName]
247 -> LHsExpr RdrName -> LHsBind RdrName
249 mk_easy_FunBind loc fun pats expr
250 = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]
253 mk_FunBind :: SrcSpan -> RdrName
254 -> [([LPat RdrName], LHsExpr RdrName)]
257 mk_FunBind loc fun [] = panic "TcGenDeriv:mk_FunBind"
258 mk_FunBind loc fun pats_and_exprs
259 = L loc $ mkFunBind (L loc fun) matches
261 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
264 mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id
265 mkMatch pats expr binds
266 = noLoc (Match (map paren pats) Nothing
267 (GRHSs (unguardedRHS expr) binds))
271 L l _ -> L l (ParPat p)
275 %************************************************************************
277 Collecting binders from HsBindGroups and HsBinds
279 %************************************************************************
281 Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.
289 it should return [x, y, f, a, b] (remember, order important).
292 collectLocalBinders :: HsLocalBinds name -> [Located name]
293 collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
294 collectLocalBinders (HsIPBinds _) = []
295 collectLocalBinders EmptyLocalBinds = []
297 collectHsValBinders :: HsValBinds name -> [Located name]
298 collectHsValBinders (ValBindsIn binds sigs) = collectHsBindLocatedBinders binds
299 collectHsValBinders (ValBindsOut binds sigs) = foldr collect_one [] binds
301 collect_one (_,binds) acc = foldrBag (collectAcc . unLoc) acc binds
303 collectAcc :: HsBind name -> [Located name] -> [Located name]
304 collectAcc (PatBind { pat_lhs = p }) acc = collectLocatedPatBinders p ++ acc
305 collectAcc (FunBind { fun_id = f }) acc = f : acc
306 collectAcc (VarBind { var_id = f }) acc = noLoc f : acc
307 collectAcc (AbsBinds { abs_exports = dbinds, abs_binds = binds }) acc
308 = [noLoc dp | (_,dp,_,_) <- dbinds] ++ acc
309 -- ++ foldr collectAcc acc binds
310 -- I don't think we want the binders from the nested binds
311 -- The only time we collect binders from a typechecked
312 -- binding (hence see AbsBinds) is in zonking in TcHsSyn
314 collectHsBindBinders :: LHsBinds name -> [name]
315 collectHsBindBinders binds = map unLoc (collectHsBindLocatedBinders binds)
317 collectHsBindLocatedBinders :: LHsBinds name -> [Located name]
318 collectHsBindLocatedBinders binds = foldrBag (collectAcc . unLoc) [] binds
322 %************************************************************************
324 Getting binders from statements
326 %************************************************************************
329 collectLStmtsBinders :: OutputableBndr id => [LStmt id] -> [Located id]
330 collectLStmtsBinders = concatMap collectLStmtBinders
332 collectStmtsBinders :: OutputableBndr id => [Stmt id] -> [Located id]
333 collectStmtsBinders = concatMap collectStmtBinders
335 collectLStmtBinders :: OutputableBndr id => LStmt id -> [Located id]
336 collectLStmtBinders = collectStmtBinders . unLoc
338 collectStmtBinders :: OutputableBndr id => Stmt id -> [Located id]
339 -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
340 collectStmtBinders (BindStmt pat _ _ _) = collectLocatedPatBinders pat
341 collectStmtBinders (LetStmt binds) = collectLocalBinders binds
342 collectStmtBinders (ExprStmt _ _ _) = []
343 collectStmtBinders (ParStmt xs) = collectLStmtsBinders
345 collectStmtBinders (RecStmt ss _ _ _ _) = collectLStmtsBinders ss
346 collectStmtBinders s = pprPanic "collectStmtBinders" (ppr s)
350 %************************************************************************
352 %* Gathering stuff out of patterns
354 %************************************************************************
356 This function @collectPatBinders@ works with the ``collectBinders''
357 functions for @HsBinds@, etc. The order in which the binders are
358 collected is important; see @HsBinds.lhs@.
360 It collects the bounds *value* variables in renamed patterns; type variables
364 collectPatBinders :: LPat a -> [a]
365 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
367 collectLocatedPatBinders :: LPat a -> [Located a]
368 collectLocatedPatBinders pat = collectl pat []
370 collectPatsBinders :: [LPat a] -> [a]
371 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
373 collectLocatedPatsBinders :: [LPat a] -> [Located a]
374 collectLocatedPatsBinders pats = foldr collectl [] pats
376 ---------------------
377 collectl (L l pat) bndrs
380 go (VarPat var) = L l var : bndrs
381 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
383 go (WildPat _) = bndrs
384 go (LazyPat pat) = collectl pat bndrs
385 go (BangPat pat) = collectl pat bndrs
386 go (AsPat a pat) = a : collectl pat bndrs
387 go (ParPat pat) = collectl pat bndrs
389 go (ListPat pats _) = foldr collectl bndrs pats
390 go (PArrPat pats _) = foldr collectl bndrs pats
391 go (TuplePat pats _ _) = foldr collectl bndrs pats
393 go (ConPatIn c ps) = foldr collectl bndrs (hsConPatArgs ps)
394 go (ConPatOut {pat_args=ps}) = foldr collectl bndrs (hsConPatArgs ps)
395 -- See Note [Dictionary binders in ConPatOut]
396 go (LitPat _) = bndrs
397 go (NPat _ _ _ _) = bndrs
398 go (NPlusKPat n _ _ _) = n : bndrs
400 go (SigPatIn pat _) = collectl pat bndrs
401 go (SigPatOut pat _) = collectl pat bndrs
402 go (TypePat ty) = bndrs
403 go (CoPat _ pat ty) = collectl (noLoc pat) bndrs
406 Note [Dictionary binders in ConPatOut]
407 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
408 Do *not* gather (a) dictionary and (b) dictionary bindings as binders
409 of a ConPatOut pattern. For most calls it doesn't matter, because
410 it's pre-typechecker and there are no ConPatOuts. But it does matter
411 more in the desugarer; for example, DsUtils.mkSelectorBinds uses
412 collectPatBinders. In a lazy pattern, for example f ~(C x y) = ...,
413 we want to generate bindings for x,y but not for dictionaries bound by
414 C. (The type checker ensures they would not be used.)
416 Desugaring of arrow case expressions needs these bindings (see DsArrows
417 and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
418 own pat-binder-collector:
420 Here's the problem. Consider
423 C :: Num a => a -> Int -> T a
425 f ~(C (n+1) m) = (n,m)
427 Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
428 and *also* uses that dictionary to match the (n+1) pattern. Yet, the
429 variables bound by the lazy pattern are n,m, *not* the dictionary d.
430 So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.
433 collectSigTysFromPats :: [InPat name] -> [LHsType name]
434 collectSigTysFromPats pats = foldr collect_lpat [] pats
436 collectSigTysFromPat :: InPat name -> [LHsType name]
437 collectSigTysFromPat pat = collect_lpat pat []
439 collect_lpat pat acc = collect_pat (unLoc pat) acc
441 collect_pat (SigPatIn pat ty) acc = collect_lpat pat (ty:acc)
442 collect_pat (TypePat ty) acc = ty:acc
444 collect_pat (LazyPat pat) acc = collect_lpat pat acc
445 collect_pat (BangPat pat) acc = collect_lpat pat acc
446 collect_pat (AsPat a pat) acc = collect_lpat pat acc
447 collect_pat (ParPat pat) acc = collect_lpat pat acc
448 collect_pat (ListPat pats _) acc = foldr collect_lpat acc pats
449 collect_pat (PArrPat pats _) acc = foldr collect_lpat acc pats
450 collect_pat (TuplePat pats _ _) acc = foldr collect_lpat acc pats
451 collect_pat (ConPatIn c ps) acc = foldr collect_lpat acc (hsConPatArgs ps)
452 collect_pat other acc = acc -- Literals, vars, wildcard