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 mkHsLam :: [LPat id] -> LHsExpr id -> LHsExpr id
98 mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
100 matches = mkMatchGroup [mkSimpleMatch pats body]
102 mkMatchGroup :: [LMatch id] -> MatchGroup id
103 mkMatchGroup matches = MatchGroup matches placeHolderType
105 mkHsDictLet :: LHsBinds Id -> LHsExpr Id -> LHsExpr Id
106 -- Used for the dictionary bindings gotten from TcSimplify
107 -- We make them recursive to be on the safe side
108 mkHsDictLet binds expr
109 | isEmptyLHsBinds binds = expr
110 | otherwise = L (getLoc expr) (HsLet (HsValBinds val_binds) expr)
112 val_binds = ValBindsOut [(Recursive, binds)] []
114 mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
115 -- Used for constructing dictionary terms etc, so no locations
116 mkHsConApp data_con tys args
117 = foldl mk_app (nlHsTyApp (dataConWrapId data_con) tys) args
119 mk_app f a = noLoc (HsApp f (noLoc a))
121 mkSimpleHsAlt :: LPat id -> LHsExpr id -> LMatch id
122 -- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
123 mkSimpleHsAlt pat expr
124 = mkSimpleMatch [pat] expr
126 -------------------------------
127 -- These are the bits of syntax that contain rebindable names
128 -- See RnEnv.lookupSyntaxName
130 mkHsIntegral i = HsIntegral i noSyntaxExpr
131 mkHsFractional f = HsFractional f noSyntaxExpr
132 mkHsIsString s = HsIsString s noSyntaxExpr
133 mkHsDo ctxt stmts body = HsDo ctxt stmts body placeHolderType
135 mkNPat lit neg = NPat lit neg noSyntaxExpr placeHolderType
136 mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr
138 mkExprStmt expr = ExprStmt expr noSyntaxExpr placeHolderType
139 mkBindStmt pat expr = BindStmt pat expr noSyntaxExpr noSyntaxExpr
140 mkRecStmt stmts = RecStmt stmts [] [] [] emptyLHsBinds
142 -------------------------------
143 --- A useful function for building @OpApps@. The operator is always a
144 -- variable, and we don't know the fixity yet.
145 mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2
147 mkHsSplice e = HsSplice unqualSplice e
149 unqualSplice = mkRdrUnqual (mkVarOccFS FSLIT("splice"))
150 -- A name (uniquified later) to
151 -- identify the splice
153 mkHsString s = HsString (mkFastString s)
156 userHsTyVarBndrs :: [Located name] -> [Located (HsTyVarBndr name)]
157 userHsTyVarBndrs bndrs = [ L loc (UserTyVar v) | L loc v <- bndrs ]
161 %************************************************************************
163 Constructing syntax with no location info
165 %************************************************************************
168 nlHsVar :: id -> LHsExpr id
169 nlHsVar n = noLoc (HsVar n)
171 nlHsLit :: HsLit -> LHsExpr id
172 nlHsLit n = noLoc (HsLit n)
174 nlVarPat :: id -> LPat id
175 nlVarPat n = noLoc (VarPat n)
177 nlLitPat :: HsLit -> LPat id
178 nlLitPat l = noLoc (LitPat l)
180 nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
181 nlHsApp f x = noLoc (HsApp f x)
183 nlHsIntLit n = noLoc (HsLit (HsInt n))
185 nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
186 nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
188 nlHsVarApps :: id -> [id] -> LHsExpr id
189 nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
191 mk f a = HsApp (noLoc f) (noLoc a)
193 nlConVarPat :: id -> [id] -> LPat id
194 nlConVarPat con vars = nlConPat con (map nlVarPat vars)
196 nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
197 nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))
199 nlConPat :: id -> [LPat id] -> LPat id
200 nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))
202 nlNullaryConPat :: id -> LPat id
203 nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))
205 nlWildConPat :: DataCon -> LPat RdrName
206 nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
207 (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))
209 nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)
210 nlWildPat = noLoc (WildPat placeHolderType) -- Pre-typechecking
212 nlHsDo :: HsStmtContext Name -> [LStmt id] -> LHsExpr id -> LHsExpr id
213 nlHsDo ctxt stmts body = noLoc (mkHsDo ctxt stmts body)
215 nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)
217 nlHsLam match = noLoc (HsLam (mkMatchGroup [match]))
218 nlHsPar e = noLoc (HsPar e)
219 nlHsIf cond true false = noLoc (HsIf cond true false)
220 nlHsCase expr matches = noLoc (HsCase expr (mkMatchGroup matches))
221 nlTuple exprs box = noLoc (ExplicitTuple exprs box)
222 nlList exprs = noLoc (ExplicitList placeHolderType exprs)
224 nlHsAppTy f t = noLoc (HsAppTy f t)
225 nlHsTyVar x = noLoc (HsTyVar x)
226 nlHsFunTy a b = noLoc (HsFunTy a b)
228 nlHsTyConApp tycon tys = foldl nlHsAppTy (nlHsTyVar tycon) tys
233 %************************************************************************
235 Bindings; with a location at the top
237 %************************************************************************
240 mkFunBind :: Located id -> [LMatch id] -> HsBind id
241 -- Not infix, with place holders for coercion and free vars
242 mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False, fun_matches = mkMatchGroup ms,
243 fun_co_fn = idHsWrapper, bind_fvs = placeHolderNames,
247 mkVarBind :: SrcSpan -> RdrName -> LHsExpr RdrName -> LHsBind RdrName
248 mkVarBind loc var rhs = mk_easy_FunBind loc var [] rhs
251 mk_easy_FunBind :: SrcSpan -> RdrName -> [LPat RdrName]
252 -> LHsExpr RdrName -> LHsBind RdrName
254 mk_easy_FunBind loc fun pats expr
255 = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]
258 mk_FunBind :: SrcSpan -> RdrName
259 -> [([LPat RdrName], LHsExpr RdrName)]
262 mk_FunBind loc fun [] = panic "TcGenDeriv:mk_FunBind"
263 mk_FunBind loc fun pats_and_exprs
264 = L loc $ mkFunBind (L loc fun) matches
266 matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs]
269 mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id
270 mkMatch pats expr binds
271 = noLoc (Match (map paren pats) Nothing
272 (GRHSs (unguardedRHS expr) binds))
276 L l _ -> L l (ParPat p)
280 %************************************************************************
282 Collecting binders from HsBindGroups and HsBinds
284 %************************************************************************
286 Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.
294 it should return [x, y, f, a, b] (remember, order important).
297 collectLocalBinders :: HsLocalBinds name -> [Located name]
298 collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
299 collectLocalBinders (HsIPBinds _) = []
300 collectLocalBinders EmptyLocalBinds = []
302 collectHsValBinders :: HsValBinds name -> [Located name]
303 collectHsValBinders (ValBindsIn binds sigs) = collectHsBindLocatedBinders binds
304 collectHsValBinders (ValBindsOut binds sigs) = foldr collect_one [] binds
306 collect_one (_,binds) acc = foldrBag (collectAcc . unLoc) acc binds
308 collectAcc :: HsBind name -> [Located name] -> [Located name]
309 collectAcc (PatBind { pat_lhs = p }) acc = collectLocatedPatBinders p ++ acc
310 collectAcc (FunBind { fun_id = f }) acc = f : acc
311 collectAcc (VarBind { var_id = f }) acc = noLoc f : acc
312 collectAcc (AbsBinds { abs_exports = dbinds, abs_binds = binds }) acc
313 = [noLoc dp | (_,dp,_,_) <- dbinds] ++ acc
314 -- ++ foldr collectAcc acc binds
315 -- I don't think we want the binders from the nested binds
316 -- The only time we collect binders from a typechecked
317 -- binding (hence see AbsBinds) is in zonking in TcHsSyn
319 collectHsBindBinders :: LHsBinds name -> [name]
320 collectHsBindBinders binds = map unLoc (collectHsBindLocatedBinders binds)
322 collectHsBindLocatedBinders :: LHsBinds name -> [Located name]
323 collectHsBindLocatedBinders binds = foldrBag (collectAcc . unLoc) [] binds
327 %************************************************************************
329 Getting binders from statements
331 %************************************************************************
334 collectLStmtsBinders :: OutputableBndr id => [LStmt id] -> [Located id]
335 collectLStmtsBinders = concatMap collectLStmtBinders
337 collectStmtsBinders :: OutputableBndr id => [Stmt id] -> [Located id]
338 collectStmtsBinders = concatMap collectStmtBinders
340 collectLStmtBinders :: OutputableBndr id => LStmt id -> [Located id]
341 collectLStmtBinders = collectStmtBinders . unLoc
343 collectStmtBinders :: OutputableBndr id => Stmt id -> [Located id]
344 -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
345 collectStmtBinders (BindStmt pat _ _ _) = collectLocatedPatBinders pat
346 collectStmtBinders (LetStmt binds) = collectLocalBinders binds
347 collectStmtBinders (ExprStmt _ _ _) = []
348 collectStmtBinders (ParStmt xs) = collectLStmtsBinders
350 collectStmtBinders (RecStmt ss _ _ _ _) = collectLStmtsBinders ss
351 collectStmtBinders s = pprPanic "collectStmtBinders" (ppr s)
355 %************************************************************************
357 %* Gathering stuff out of patterns
359 %************************************************************************
361 This function @collectPatBinders@ works with the ``collectBinders''
362 functions for @HsBinds@, etc. The order in which the binders are
363 collected is important; see @HsBinds.lhs@.
365 It collects the bounds *value* variables in renamed patterns; type variables
369 collectPatBinders :: LPat a -> [a]
370 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
372 collectLocatedPatBinders :: LPat a -> [Located a]
373 collectLocatedPatBinders pat = collectl pat []
375 collectPatsBinders :: [LPat a] -> [a]
376 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
378 collectLocatedPatsBinders :: [LPat a] -> [Located a]
379 collectLocatedPatsBinders pats = foldr collectl [] pats
381 ---------------------
382 collectl (L l pat) bndrs
385 go (VarPat var) = L l var : bndrs
386 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
388 go (WildPat _) = bndrs
389 go (LazyPat pat) = collectl pat bndrs
390 go (BangPat pat) = collectl pat bndrs
391 go (AsPat a pat) = a : collectl pat bndrs
392 go (ParPat pat) = collectl pat bndrs
394 go (ListPat pats _) = foldr collectl bndrs pats
395 go (PArrPat pats _) = foldr collectl bndrs pats
396 go (TuplePat pats _ _) = foldr collectl bndrs pats
398 go (ConPatIn c ps) = foldr collectl bndrs (hsConPatArgs ps)
399 go (ConPatOut {pat_args=ps}) = foldr collectl bndrs (hsConPatArgs ps)
400 -- See Note [Dictionary binders in ConPatOut]
401 go (LitPat _) = bndrs
402 go (NPat _ _ _ _) = bndrs
403 go (NPlusKPat n _ _ _) = n : bndrs
405 go (SigPatIn pat _) = collectl pat bndrs
406 go (SigPatOut pat _) = collectl pat bndrs
407 go (TypePat ty) = bndrs
408 go (CoPat _ pat ty) = collectl (noLoc pat) bndrs
411 Note [Dictionary binders in ConPatOut]
412 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
413 Do *not* gather (a) dictionary and (b) dictionary bindings as binders
414 of a ConPatOut pattern. For most calls it doesn't matter, because
415 it's pre-typechecker and there are no ConPatOuts. But it does matter
416 more in the desugarer; for example, DsUtils.mkSelectorBinds uses
417 collectPatBinders. In a lazy pattern, for example f ~(C x y) = ...,
418 we want to generate bindings for x,y but not for dictionaries bound by
419 C. (The type checker ensures they would not be used.)
421 Desugaring of arrow case expressions needs these bindings (see DsArrows
422 and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
423 own pat-binder-collector:
425 Here's the problem. Consider
428 C :: Num a => a -> Int -> T a
430 f ~(C (n+1) m) = (n,m)
432 Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
433 and *also* uses that dictionary to match the (n+1) pattern. Yet, the
434 variables bound by the lazy pattern are n,m, *not* the dictionary d.
435 So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.
438 collectSigTysFromPats :: [InPat name] -> [LHsType name]
439 collectSigTysFromPats pats = foldr collect_lpat [] pats
441 collectSigTysFromPat :: InPat name -> [LHsType name]
442 collectSigTysFromPat pat = collect_lpat pat []
444 collect_lpat pat acc = collect_pat (unLoc pat) acc
446 collect_pat (SigPatIn pat ty) acc = collect_lpat pat (ty:acc)
447 collect_pat (TypePat ty) acc = ty:acc
449 collect_pat (LazyPat pat) acc = collect_lpat pat acc
450 collect_pat (BangPat pat) acc = collect_lpat pat acc
451 collect_pat (AsPat a pat) acc = collect_lpat pat acc
452 collect_pat (ParPat pat) acc = collect_lpat pat acc
453 collect_pat (ListPat pats _) acc = foldr collect_lpat acc pats
454 collect_pat (PArrPat pats _) acc = foldr collect_lpat acc pats
455 collect_pat (TuplePat pats _ _) acc = foldr collect_lpat acc pats
456 collect_pat (ConPatIn c ps) acc = foldr collect_lpat acc (hsConPatArgs ps)
457 collect_pat other acc = acc -- Literals, vars, wildcard