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"
48 %************************************************************************
50 Some useful helpers for constructing syntax
52 %************************************************************************
54 These functions attempt to construct a not-completely-useless SrcSpan
55 from their components, compared with the nl* functions below which
56 just attach noSrcSpan to everything.
59 mkHsPar :: LHsExpr id -> LHsExpr id
60 mkHsPar e = L (getLoc e) (HsPar e)
62 mkSimpleMatch :: [LPat id] -> LHsExpr id -> LMatch id
63 mkSimpleMatch pats rhs
65 Match pats Nothing (unguardedGRHSs rhs)
69 (pat:_) -> combineSrcSpans (getLoc pat) (getLoc rhs)
71 unguardedGRHSs :: LHsExpr id -> GRHSs id
72 unguardedGRHSs rhs = GRHSs (unguardedRHS rhs) emptyLocalBinds
74 unguardedRHS :: LHsExpr id -> [LGRHS id]
75 unguardedRHS rhs@(L loc _) = [L loc (GRHS [] rhs)]
77 mkHsAppTy :: LHsType name -> LHsType name -> LHsType name
78 mkHsAppTy t1 t2 = addCLoc t1 t2 (HsAppTy t1 t2)
80 mkHsApp :: LHsExpr name -> LHsExpr name -> LHsExpr name
81 mkHsApp e1 e2 = addCLoc e1 e2 (HsApp e1 e2)
83 nlHsTyApp :: name -> [Type] -> LHsExpr name
84 nlHsTyApp fun_id tys = noLoc (HsWrap (mkWpTyApps tys) (HsVar fun_id))
86 mkLHsWrap :: HsWrapper -> LHsExpr id -> LHsExpr id
87 mkLHsWrap co_fn (L loc e) = L loc (mkHsWrap co_fn e)
89 mkHsWrap :: HsWrapper -> HsExpr id -> HsExpr id
90 mkHsWrap co_fn e | isIdHsWrapper co_fn = e
91 | otherwise = HsWrap co_fn e
93 mkHsWrapCoI :: CoercionI -> HsExpr id -> HsExpr id
94 mkHsWrapCoI IdCo e = e
95 mkHsWrapCoI (ACo co) e = mkHsWrap (WpCo co) e
97 coiToHsWrapper :: CoercionI -> HsWrapper
98 coiToHsWrapper IdCo = idHsWrapper
99 coiToHsWrapper (ACo co) = WpCo co
101 mkHsLam :: [LPat id] -> LHsExpr id -> LHsExpr id
102 mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
104 matches = mkMatchGroup [mkSimpleMatch pats body]
106 mkMatchGroup :: [LMatch id] -> MatchGroup id
107 mkMatchGroup matches = MatchGroup matches placeHolderType
109 mkHsDictLet :: LHsBinds Id -> LHsExpr Id -> LHsExpr Id
110 -- Used for the dictionary bindings gotten from TcSimplify
111 -- We make them recursive to be on the safe side
112 mkHsDictLet binds expr
113 | isEmptyLHsBinds binds = expr
114 | otherwise = L (getLoc expr) (HsLet (HsValBinds val_binds) expr)
116 val_binds = ValBindsOut [(Recursive, binds)] []
118 mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
119 -- Used for constructing dictionary terms etc, so no locations
120 mkHsConApp data_con tys args
121 = foldl mk_app (nlHsTyApp (dataConWrapId data_con) tys) args
123 mk_app f a = noLoc (HsApp f (noLoc a))
125 mkSimpleHsAlt :: LPat id -> LHsExpr id -> LMatch id
126 -- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
127 mkSimpleHsAlt pat expr
128 = mkSimpleMatch [pat] expr
130 -------------------------------
131 -- These are the bits of syntax that contain rebindable names
132 -- See RnEnv.lookupSyntaxName
134 mkHsIntegral i = HsIntegral i noSyntaxExpr
135 mkHsFractional f = HsFractional f noSyntaxExpr
136 mkHsIsString s = HsIsString s noSyntaxExpr
137 mkHsDo ctxt stmts body = HsDo ctxt stmts body placeHolderType
139 mkNPat lit neg = NPat lit neg noSyntaxExpr
140 mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr
142 mkExprStmt expr = ExprStmt expr noSyntaxExpr placeHolderType
143 mkBindStmt pat expr = BindStmt pat expr noSyntaxExpr noSyntaxExpr
144 mkRecStmt stmts = RecStmt stmts [] [] [] emptyLHsBinds
146 -------------------------------
147 --- A useful function for building @OpApps@. The operator is always a
148 -- variable, and we don't know the fixity yet.
149 mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2
151 mkHsSplice e = HsSplice unqualSplice e
153 unqualSplice = mkRdrUnqual (mkVarOccFS FSLIT("splice"))
154 -- A name (uniquified later) to
155 -- identify the splice
157 mkHsString s = HsString (mkFastString s)
160 userHsTyVarBndrs :: [Located name] -> [Located (HsTyVarBndr name)]
161 userHsTyVarBndrs bndrs = [ L loc (UserTyVar v) | L loc v <- bndrs ]
165 %************************************************************************
167 Constructing syntax with no location info
169 %************************************************************************
172 nlHsVar :: id -> LHsExpr id
173 nlHsVar n = noLoc (HsVar n)
175 nlHsLit :: HsLit -> LHsExpr id
176 nlHsLit n = noLoc (HsLit n)
178 nlVarPat :: id -> LPat id
179 nlVarPat n = noLoc (VarPat n)
181 nlLitPat :: HsLit -> LPat id
182 nlLitPat l = noLoc (LitPat l)
184 nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
185 nlHsApp f x = noLoc (HsApp f x)
187 nlHsIntLit n = noLoc (HsLit (HsInt n))
189 nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
190 nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
192 nlHsVarApps :: id -> [id] -> LHsExpr id
193 nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
195 mk f a = HsApp (noLoc f) (noLoc a)
197 nlConVarPat :: id -> [id] -> LPat id
198 nlConVarPat con vars = nlConPat con (map nlVarPat vars)
200 nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
201 nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))
203 nlConPat :: id -> [LPat id] -> LPat id
204 nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))
206 nlNullaryConPat :: id -> LPat id
207 nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))
209 nlWildConPat :: DataCon -> LPat RdrName
210 nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
211 (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))
213 nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)
214 nlWildPat = noLoc (WildPat placeHolderType) -- Pre-typechecking
216 nlHsDo :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> LHsExpr id
217 nlHsDo ctxt stmts body = noLoc (mkHsDo ctxt stmts body)
219 nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)
221 nlHsLam match = noLoc (HsLam (mkMatchGroup [match]))
222 nlHsPar e = noLoc (HsPar e)
223 nlHsIf cond true false = noLoc (HsIf cond true false)
224 nlHsCase expr matches = noLoc (HsCase expr (mkMatchGroup matches))
225 nlTuple exprs box = noLoc (ExplicitTuple exprs box)
226 nlList exprs = noLoc (ExplicitList placeHolderType exprs)
228 nlHsAppTy f t = noLoc (HsAppTy f t)
229 nlHsTyVar x = noLoc (HsTyVar x)
230 nlHsFunTy a b = noLoc (HsFunTy a b)
232 nlHsTyConApp tycon tys = foldl nlHsAppTy (nlHsTyVar tycon) tys
237 %************************************************************************
239 Bindings; with a location at the top
241 %************************************************************************
244 mkFunBind :: Located id -> [LMatch id] -> HsBind id
245 -- Not infix, with place holders for coercion and free vars
246 mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False, fun_matches = mkMatchGroup ms,
247 fun_co_fn = idHsWrapper, bind_fvs = placeHolderNames,
251 mkVarBind :: SrcSpan -> id -> LHsExpr id -> LHsBind id
252 mkVarBind loc var rhs = mk_easy_FunBind loc var [] rhs
255 mk_easy_FunBind :: SrcSpan -> id -> [LPat id]
256 -> LHsExpr id -> LHsBind id
258 mk_easy_FunBind loc fun pats expr
259 = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]
262 mk_FunBind :: SrcSpan -> id
263 -> [([LPat id], LHsExpr id)]
266 mk_FunBind loc fun [] = panic "TcGenDeriv:mk_FunBind"
267 mk_FunBind loc fun pats_and_exprs
268 = L loc $ mkFunBind (L loc fun) matches
270 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
273 mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id
274 mkMatch pats expr binds
275 = noLoc (Match (map paren pats) Nothing
276 (GRHSs (unguardedRHS expr) binds))
280 L l _ -> L l (ParPat p)
284 %************************************************************************
286 Collecting binders from HsBindGroups and HsBinds
288 %************************************************************************
290 Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.
298 it should return [x, y, f, a, b] (remember, order important).
301 collectLocalBinders :: HsLocalBindsLR idL idR -> [Located idL]
302 collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
303 collectLocalBinders (HsIPBinds _) = []
304 collectLocalBinders EmptyLocalBinds = []
306 collectHsValBinders :: HsValBindsLR idL idR -> [Located idL]
307 collectHsValBinders (ValBindsIn binds sigs) = collectHsBindLocatedBinders binds
308 collectHsValBinders (ValBindsOut binds sigs) = foldr collect_one [] binds
310 collect_one (_,binds) acc = foldrBag (collectAcc . unLoc) acc binds
312 collectAcc :: HsBindLR idL idR -> [Located idL] -> [Located idL]
313 collectAcc (PatBind { pat_lhs = p }) acc = collectLocatedPatBinders p ++ acc
314 collectAcc (FunBind { fun_id = f }) acc = f : acc
315 collectAcc (VarBind { var_id = f }) acc = noLoc f : acc
316 collectAcc (AbsBinds { abs_exports = dbinds, abs_binds = binds }) acc
317 = [noLoc dp | (_,dp,_,_) <- dbinds] ++ acc
318 -- ++ foldr collectAcc acc binds
319 -- I don't think we want the binders from the nested binds
320 -- The only time we collect binders from a typechecked
321 -- binding (hence see AbsBinds) is in zonking in TcHsSyn
323 collectHsBindBinders :: LHsBindsLR idL idR -> [idL]
324 collectHsBindBinders binds = map unLoc (collectHsBindLocatedBinders binds)
326 collectHsBindLocatedBinders :: LHsBindsLR idL idR -> [Located idL]
327 collectHsBindLocatedBinders binds = foldrBag (collectAcc . unLoc) [] binds
331 %************************************************************************
333 Getting binders from statements
335 %************************************************************************
338 collectLStmtsBinders :: [LStmtLR idL idR] -> [Located idL]
339 collectLStmtsBinders = concatMap collectLStmtBinders
341 collectStmtsBinders :: [StmtLR idL idR] -> [Located idL]
342 collectStmtsBinders = concatMap collectStmtBinders
344 collectLStmtBinders :: LStmtLR idL idR -> [Located idL]
345 collectLStmtBinders = collectStmtBinders . unLoc
347 collectStmtBinders :: StmtLR idL idR -> [Located idL]
348 -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
349 collectStmtBinders (BindStmt pat _ _ _) = collectLocatedPatBinders pat
350 collectStmtBinders (LetStmt binds) = collectLocalBinders binds
351 collectStmtBinders (ExprStmt _ _ _) = []
352 collectStmtBinders (ParStmt xs) = collectLStmtsBinders
354 collectStmtBinders (RecStmt ss _ _ _ _) = collectLStmtsBinders ss
358 %************************************************************************
360 %* Gathering stuff out of patterns
362 %************************************************************************
364 This function @collectPatBinders@ works with the ``collectBinders''
365 functions for @HsBinds@, etc. The order in which the binders are
366 collected is important; see @HsBinds.lhs@.
368 It collects the bounds *value* variables in renamed patterns; type variables
372 collectPatBinders :: LPat a -> [a]
373 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
375 collectLocatedPatBinders :: LPat a -> [Located a]
376 collectLocatedPatBinders pat = collectl pat []
378 collectPatsBinders :: [LPat a] -> [a]
379 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
381 collectLocatedPatsBinders :: [LPat a] -> [Located a]
382 collectLocatedPatsBinders pats = foldr collectl [] pats
384 ---------------------
385 collectl (L l pat) bndrs
388 go (VarPat var) = L l var : bndrs
389 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
391 go (WildPat _) = bndrs
392 go (LazyPat pat) = collectl pat bndrs
393 go (BangPat pat) = collectl pat bndrs
394 go (AsPat a pat) = a : collectl pat bndrs
395 go (ViewPat exp pat _) = collectl pat bndrs
396 go (ParPat pat) = collectl pat bndrs
398 go (ListPat pats _) = foldr collectl bndrs pats
399 go (PArrPat pats _) = foldr collectl bndrs pats
400 go (TuplePat pats _ _) = foldr collectl bndrs pats
402 go (ConPatIn c ps) = foldr collectl bndrs (hsConPatArgs ps)
403 go (ConPatOut {pat_args=ps}) = foldr collectl bndrs (hsConPatArgs ps)
404 -- See Note [Dictionary binders in ConPatOut]
405 go (LitPat _) = bndrs
406 go (NPat _ _ _) = bndrs
407 go (NPlusKPat n _ _ _) = n : bndrs
409 go (SigPatIn pat _) = collectl pat bndrs
410 go (SigPatOut pat _) = collectl pat bndrs
411 go (TypePat ty) = bndrs
412 go (CoPat _ pat ty) = collectl (noLoc pat) bndrs
415 Note [Dictionary binders in ConPatOut]
416 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
417 Do *not* gather (a) dictionary and (b) dictionary bindings as binders
418 of a ConPatOut pattern. For most calls it doesn't matter, because
419 it's pre-typechecker and there are no ConPatOuts. But it does matter
420 more in the desugarer; for example, DsUtils.mkSelectorBinds uses
421 collectPatBinders. In a lazy pattern, for example f ~(C x y) = ...,
422 we want to generate bindings for x,y but not for dictionaries bound by
423 C. (The type checker ensures they would not be used.)
425 Desugaring of arrow case expressions needs these bindings (see DsArrows
426 and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
427 own pat-binder-collector:
429 Here's the problem. Consider
432 C :: Num a => a -> Int -> T a
434 f ~(C (n+1) m) = (n,m)
436 Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
437 and *also* uses that dictionary to match the (n+1) pattern. Yet, the
438 variables bound by the lazy pattern are n,m, *not* the dictionary d.
439 So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.
442 collectSigTysFromPats :: [InPat name] -> [LHsType name]
443 collectSigTysFromPats pats = foldr collect_lpat [] pats
445 collectSigTysFromPat :: InPat name -> [LHsType name]
446 collectSigTysFromPat pat = collect_lpat pat []
448 collect_lpat pat acc = collect_pat (unLoc pat) acc
450 collect_pat (SigPatIn pat ty) acc = collect_lpat pat (ty:acc)
451 collect_pat (TypePat ty) acc = ty:acc
453 collect_pat (LazyPat pat) acc = collect_lpat pat acc
454 collect_pat (BangPat pat) acc = collect_lpat pat acc
455 collect_pat (AsPat a pat) acc = collect_lpat pat acc
456 collect_pat (ParPat pat) acc = collect_lpat pat acc
457 collect_pat (ListPat pats _) acc = foldr collect_lpat acc pats
458 collect_pat (PArrPat pats _) acc = foldr collect_lpat acc pats
459 collect_pat (TuplePat pats _ _) acc = foldr collect_lpat acc pats
460 collect_pat (ConPatIn c ps) acc = foldr collect_lpat acc (hsConPatArgs ps)
461 collect_pat other acc = acc -- Literals, vars, wildcard