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 mkTransformStmt stmts usingExpr = TransformStmt (stmts, []) usingExpr Nothing
143 mkTransformByStmt stmts usingExpr byExpr = TransformStmt (stmts, []) usingExpr (Just byExpr)
145 mkGroupUsingStmt stmts usingExpr = GroupStmt (stmts, []) (GroupByNothing usingExpr)
146 mkGroupByStmt stmts byExpr = GroupStmt (stmts, []) (GroupBySomething (Right noSyntaxExpr) byExpr)
147 mkGroupByUsingStmt stmts byExpr usingExpr = GroupStmt (stmts, []) (GroupBySomething (Left usingExpr) byExpr)
149 mkExprStmt expr = ExprStmt expr noSyntaxExpr placeHolderType
150 mkBindStmt pat expr = BindStmt pat expr noSyntaxExpr noSyntaxExpr
151 mkRecStmt stmts = RecStmt stmts [] [] [] emptyLHsBinds
153 -------------------------------
154 --- A useful function for building @OpApps@. The operator is always a
155 -- variable, and we don't know the fixity yet.
156 mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2
158 mkHsSplice e = HsSplice unqualSplice e
160 unqualSplice = mkRdrUnqual (mkVarOccFS FSLIT("splice"))
161 -- A name (uniquified later) to
162 -- identify the splice
164 mkHsString s = HsString (mkFastString s)
167 userHsTyVarBndrs :: [Located name] -> [Located (HsTyVarBndr name)]
168 userHsTyVarBndrs bndrs = [ L loc (UserTyVar v) | L loc v <- bndrs ]
172 %************************************************************************
174 Constructing syntax with no location info
176 %************************************************************************
179 nlHsVar :: id -> LHsExpr id
180 nlHsVar n = noLoc (HsVar n)
182 nlHsLit :: HsLit -> LHsExpr id
183 nlHsLit n = noLoc (HsLit n)
185 nlVarPat :: id -> LPat id
186 nlVarPat n = noLoc (VarPat n)
188 nlLitPat :: HsLit -> LPat id
189 nlLitPat l = noLoc (LitPat l)
191 nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
192 nlHsApp f x = noLoc (HsApp f x)
194 nlHsIntLit n = noLoc (HsLit (HsInt n))
196 nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
197 nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
199 nlHsVarApps :: id -> [id] -> LHsExpr id
200 nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
202 mk f a = HsApp (noLoc f) (noLoc a)
204 nlConVarPat :: id -> [id] -> LPat id
205 nlConVarPat con vars = nlConPat con (map nlVarPat vars)
207 nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
208 nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))
210 nlConPat :: id -> [LPat id] -> LPat id
211 nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))
213 nlNullaryConPat :: id -> LPat id
214 nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))
216 nlWildConPat :: DataCon -> LPat RdrName
217 nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
218 (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))
220 nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)
221 nlWildPat = noLoc (WildPat placeHolderType) -- Pre-typechecking
223 nlHsDo :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> LHsExpr id
224 nlHsDo ctxt stmts body = noLoc (mkHsDo ctxt stmts body)
226 nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)
228 nlHsLam match = noLoc (HsLam (mkMatchGroup [match]))
229 nlHsPar e = noLoc (HsPar e)
230 nlHsIf cond true false = noLoc (HsIf cond true false)
231 nlHsCase expr matches = noLoc (HsCase expr (mkMatchGroup matches))
232 nlTuple exprs box = noLoc (ExplicitTuple exprs box)
233 nlList exprs = noLoc (ExplicitList placeHolderType exprs)
235 nlHsAppTy f t = noLoc (HsAppTy f t)
236 nlHsTyVar x = noLoc (HsTyVar x)
237 nlHsFunTy a b = noLoc (HsFunTy a b)
239 nlHsTyConApp tycon tys = foldl nlHsAppTy (nlHsTyVar tycon) tys
244 %************************************************************************
246 Bindings; with a location at the top
248 %************************************************************************
251 mkFunBind :: Located id -> [LMatch id] -> HsBind id
252 -- Not infix, with place holders for coercion and free vars
253 mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False, fun_matches = mkMatchGroup ms,
254 fun_co_fn = idHsWrapper, bind_fvs = placeHolderNames,
258 mkVarBind :: SrcSpan -> id -> LHsExpr id -> LHsBind id
259 mkVarBind loc var rhs = mk_easy_FunBind loc var [] rhs
262 mk_easy_FunBind :: SrcSpan -> id -> [LPat id]
263 -> LHsExpr id -> LHsBind id
265 mk_easy_FunBind loc fun pats expr
266 = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]
269 mk_FunBind :: SrcSpan -> id
270 -> [([LPat id], LHsExpr id)]
273 mk_FunBind loc fun [] = panic "TcGenDeriv:mk_FunBind"
274 mk_FunBind loc fun pats_and_exprs
275 = L loc $ mkFunBind (L loc fun) matches
277 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
280 mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id
281 mkMatch pats expr binds
282 = noLoc (Match (map paren pats) Nothing
283 (GRHSs (unguardedRHS expr) binds))
287 L l _ -> L l (ParPat p)
291 %************************************************************************
293 Collecting binders from HsBindGroups and HsBinds
295 %************************************************************************
297 Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.
305 it should return [x, y, f, a, b] (remember, order important).
308 collectLocalBinders :: HsLocalBindsLR idL idR -> [Located idL]
309 collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
310 collectLocalBinders (HsIPBinds _) = []
311 collectLocalBinders EmptyLocalBinds = []
313 collectHsValBinders :: HsValBindsLR idL idR -> [Located idL]
314 collectHsValBinders (ValBindsIn binds sigs) = collectHsBindLocatedBinders binds
315 collectHsValBinders (ValBindsOut binds sigs) = foldr collect_one [] binds
317 collect_one (_,binds) acc = foldrBag (collectAcc . unLoc) acc binds
319 collectAcc :: HsBindLR idL idR -> [Located idL] -> [Located idL]
320 collectAcc (PatBind { pat_lhs = p }) acc = collectLocatedPatBinders p ++ acc
321 collectAcc (FunBind { fun_id = f }) acc = f : acc
322 collectAcc (VarBind { var_id = f }) acc = noLoc f : acc
323 collectAcc (AbsBinds { abs_exports = dbinds, abs_binds = binds }) acc
324 = [noLoc dp | (_,dp,_,_) <- dbinds] ++ acc
325 -- ++ foldr collectAcc acc binds
326 -- I don't think we want the binders from the nested binds
327 -- The only time we collect binders from a typechecked
328 -- binding (hence see AbsBinds) is in zonking in TcHsSyn
330 collectHsBindBinders :: LHsBindsLR idL idR -> [idL]
331 collectHsBindBinders binds = map unLoc (collectHsBindLocatedBinders binds)
333 collectHsBindLocatedBinders :: LHsBindsLR idL idR -> [Located idL]
334 collectHsBindLocatedBinders binds = foldrBag (collectAcc . unLoc) [] binds
338 %************************************************************************
340 Getting binders from statements
342 %************************************************************************
345 collectLStmtsBinders :: [LStmtLR idL idR] -> [Located idL]
346 collectLStmtsBinders = concatMap collectLStmtBinders
348 collectStmtsBinders :: [StmtLR idL idR] -> [Located idL]
349 collectStmtsBinders = concatMap collectStmtBinders
351 collectLStmtBinders :: LStmtLR idL idR -> [Located idL]
352 collectLStmtBinders = collectStmtBinders . unLoc
354 collectStmtBinders :: StmtLR idL idR -> [Located idL]
355 -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
356 collectStmtBinders (BindStmt pat _ _ _) = collectLocatedPatBinders pat
357 collectStmtBinders (LetStmt binds) = collectLocalBinders binds
358 collectStmtBinders (ExprStmt _ _ _) = []
359 collectStmtBinders (ParStmt xs) = collectLStmtsBinders
361 collectStmtBinders (TransformStmt (stmts, _) _ _) = collectLStmtsBinders stmts
362 collectStmtBinders (GroupStmt (stmts, _) _) = collectLStmtsBinders stmts
363 collectStmtBinders (RecStmt ss _ _ _ _) = collectLStmtsBinders ss
367 %************************************************************************
369 %* Gathering stuff out of patterns
371 %************************************************************************
373 This function @collectPatBinders@ works with the ``collectBinders''
374 functions for @HsBinds@, etc. The order in which the binders are
375 collected is important; see @HsBinds.lhs@.
377 It collects the bounds *value* variables in renamed patterns; type variables
381 collectPatBinders :: LPat a -> [a]
382 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
384 collectLocatedPatBinders :: LPat a -> [Located a]
385 collectLocatedPatBinders pat = collectl pat []
387 collectPatsBinders :: [LPat a] -> [a]
388 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
390 collectLocatedPatsBinders :: [LPat a] -> [Located a]
391 collectLocatedPatsBinders pats = foldr collectl [] pats
393 ---------------------
394 collectl (L l pat) bndrs
397 go (VarPat var) = L l var : bndrs
398 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
400 go (WildPat _) = bndrs
401 go (LazyPat pat) = collectl pat bndrs
402 go (BangPat pat) = collectl pat bndrs
403 go (AsPat a pat) = a : collectl pat bndrs
404 go (ViewPat exp pat _) = collectl pat bndrs
405 go (ParPat pat) = collectl pat bndrs
407 go (ListPat pats _) = foldr collectl bndrs pats
408 go (PArrPat pats _) = foldr collectl bndrs pats
409 go (TuplePat pats _ _) = foldr collectl bndrs pats
411 go (ConPatIn c ps) = foldr collectl bndrs (hsConPatArgs ps)
412 go (ConPatOut {pat_args=ps}) = foldr collectl bndrs (hsConPatArgs ps)
413 -- See Note [Dictionary binders in ConPatOut]
414 go (LitPat _) = bndrs
415 go (NPat _ _ _) = bndrs
416 go (NPlusKPat n _ _ _) = n : bndrs
418 go (SigPatIn pat _) = collectl pat bndrs
419 go (SigPatOut pat _) = collectl pat bndrs
420 go (TypePat ty) = bndrs
421 go (CoPat _ pat ty) = collectl (noLoc pat) bndrs
424 Note [Dictionary binders in ConPatOut]
425 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
426 Do *not* gather (a) dictionary and (b) dictionary bindings as binders
427 of a ConPatOut pattern. For most calls it doesn't matter, because
428 it's pre-typechecker and there are no ConPatOuts. But it does matter
429 more in the desugarer; for example, DsUtils.mkSelectorBinds uses
430 collectPatBinders. In a lazy pattern, for example f ~(C x y) = ...,
431 we want to generate bindings for x,y but not for dictionaries bound by
432 C. (The type checker ensures they would not be used.)
434 Desugaring of arrow case expressions needs these bindings (see DsArrows
435 and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
436 own pat-binder-collector:
438 Here's the problem. Consider
441 C :: Num a => a -> Int -> T a
443 f ~(C (n+1) m) = (n,m)
445 Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
446 and *also* uses that dictionary to match the (n+1) pattern. Yet, the
447 variables bound by the lazy pattern are n,m, *not* the dictionary d.
448 So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.
451 collectSigTysFromPats :: [InPat name] -> [LHsType name]
452 collectSigTysFromPats pats = foldr collect_lpat [] pats
454 collectSigTysFromPat :: InPat name -> [LHsType name]
455 collectSigTysFromPat pat = collect_lpat pat []
457 collect_lpat pat acc = collect_pat (unLoc pat) acc
459 collect_pat (SigPatIn pat ty) acc = collect_lpat pat (ty:acc)
460 collect_pat (TypePat ty) acc = ty:acc
462 collect_pat (LazyPat pat) acc = collect_lpat pat acc
463 collect_pat (BangPat pat) acc = collect_lpat pat acc
464 collect_pat (AsPat a pat) acc = collect_lpat pat acc
465 collect_pat (ParPat pat) acc = collect_lpat pat acc
466 collect_pat (ListPat pats _) acc = foldr collect_lpat acc pats
467 collect_pat (PArrPat pats _) acc = foldr collect_lpat acc pats
468 collect_pat (TuplePat pats _ _) acc = foldr collect_lpat acc pats
469 collect_pat (ConPatIn c ps) acc = foldr collect_lpat acc (hsConPatArgs ps)
470 collect_pat other acc = acc -- Literals, vars, wildcard