TcBinds.hs 74.7 KB
 Austin Seipp committed Dec 03, 2014 1 2 3 4 {- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998  partain committed Jan 08, 1996 5 \section[TcBinds]{TcBinds}  Austin Seipp committed Dec 03, 2014 6 -}  partain committed Jan 08, 1996 7   Herbert Valerio Riedel committed May 15, 2014 8 9 {-# LANGUAGE CPP, RankNTypes, ScopedTypeVariables #-}  Simon Peyton Jones committed Nov 29, 2011 10 module TcBinds ( tcLocalBinds, tcTopBinds, tcRecSelBinds,  Simon Peyton Jones committed Sep 17, 2012 11  tcHsBootSigs, tcPolyCheck,  Simon Peyton Jones committed Jan 14, 2015 12 13 14  PragFun, tcSpecPrags, tcSpecWrapper, tcVectDecls, TcSigInfo(..), TcSigFun, mkPragFun,  Simon Peyton Jones committed Mar 07, 2014 15  instTcTySig, instTcTySigFromId, findScopedTyVars,  Facundo Domínguez committed Dec 09, 2014 16  badBootDeclErr, mkExport ) where  partain committed Jan 08, 1996 17   ross committed Sep 20, 2003 18 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )  simonpj@microsoft.com committed Jan 25, 2006 19 import {-# SOURCE #-} TcExpr ( tcMonoExpr )  Simon Peyton Jones committed Nov 21, 2014 20 import {-# SOURCE #-} TcPatSyn ( tcInferPatSynDecl, tcCheckPatSynDecl, tcPatSynBuilderBind )  Simon Marlow committed Oct 11, 2006 21 22 import DynFlags import HsSyn  Edward Z. Yang committed Oct 24, 2014 23 import HscTypes( isHsBootOrSig )  simonpj committed Sep 13, 2002 24 import TcRnMonad  Simon Marlow committed Oct 11, 2006 25 26 27 import TcEnv import TcUnify import TcSimplify  Simon Peyton Jones committed Dec 05, 2011 28 import TcEvidence  Simon Marlow committed Oct 11, 2006 29 30 31 import TcHsType import TcPat import TcMType  cactus committed Jan 20, 2014 32 import ConLike  Simon Peyton Jones committed Jan 14, 2015 33 import Inst( deeplyInstantiate )  Simon Peyton Jones committed Nov 04, 2014 34 35 import FamInstEnv( normaliseType ) import FamInst( tcGetFamInstEnvs )  thomasw committed Nov 28, 2014 36 import Type( pprSigmaTypeExtraCts )  chak@cse.unsw.edu.au. committed Aug 19, 2011 37 import TyCon  Simon Marlow committed Oct 11, 2006 38 39 40 import TcType import TysPrim import Id  41 import Var  Simon Peyton Jones committed Aug 16, 2011 42 import VarSet  Simon Peyton Jones committed Jun 11, 2014 43 import VarEnv( TidyEnv )  ian@well-typed.com committed Nov 02, 2012 44 import Module  Simon Marlow committed Oct 11, 2006 45 import Name  simonpj committed May 18, 1999 46 import NameSet  simonpj committed Jul 19, 2005 47 import NameEnv  Simon Marlow committed Oct 11, 2006 48 import SrcLoc  simonm committed Dec 02, 1998 49 import Bag  chak@cse.unsw.edu.au. committed Feb 20, 2011 50 import ListSetOps  Simon Marlow committed Oct 11, 2006 51 52 53 54 55 import ErrUtils import Digraph import Maybes import Util import BasicTypes  simonm committed Jan 08, 1998 56 import Outputable  Ian Lynagh committed Mar 29, 2008 57 import FastString  Simon Peyton Jones committed Jun 13, 2012 58 59 60 import Type(mkStrLitTy) import Class(classTyCon) import PrelNames(ipClassName)  Simon Peyton Jones committed Jun 11, 2014 61 import TcValidity (checkValidType)  twanvl committed Jan 17, 2008 62 63  import Control.Monad  cactus committed Nov 20, 2014 64 import Data.List (partition)  simonpj@microsoft.com committed Oct 07, 2010 65 66  #include "HsVersions.h"  simonpj committed Mar 14, 1997 67   Austin Seipp committed Dec 03, 2014 68 69 70 {- ************************************************************************ * *  partain committed Jan 08, 1996 71 \subsection{Type-checking bindings}  Austin Seipp committed Dec 03, 2014 72 73 * * ************************************************************************  partain committed Jan 08, 1996 74   partain committed Mar 19, 1996 75 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because  partain committed Jan 08, 1996 76 77 78 79 80 81 82 83 84 85 it needs to know something about the {\em usage} of the things bound, so that it can create specialisations of them. So @tcBindsAndThen@ takes a function which, given an extended environment, E, typechecks the scope of the bindings returning a typechecked thing and (most important) an LIE. It is this LIE which is then used as the basis for specialising the things bound. @tcBindsAndThen@ also takes a "combiner" which glues together the bindings and the "thing" to make a new "thing".  simonpj committed Mar 14, 1997 86 The real work is done by @tcBindWithSigsAndThen@.  partain committed Jan 08, 1996 87 88 89 90 91 92 93 94 95 96  Recursive and non-recursive binds are handled in essentially the same way: because of uniques there are no scoping issues left. The only difference is that non-recursive bindings can bind primitive values. Even for non-recursive binding groups we add typings for each binder to the LVE for the following reason. When each individual binding is checked the type of its LHS is unified with that of its RHS; and type-checking the LHS of course requires that the binder is in scope.  partain committed Mar 19, 1996 97 98 99 At the top-level the LIE is sure to contain nothing but constant dictionaries, which we resolve at the module level.  Simon Peyton Jones committed Mar 02, 2012 100 101 Note [Polymorphic recursion] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~  cactus committed Nov 20, 2014 102 The game plan for polymorphic recursion in the code above is  Simon Peyton Jones committed Mar 02, 2012 103 104  * Bind any variable for which we have a type signature  cactus committed Nov 20, 2014 105  to an Id with a polymorphic type. Then when type-checking  Simon Peyton Jones committed Mar 02, 2012 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157  the RHSs we'll make a full polymorphic call. This fine, but if you aren't a bit careful you end up with a horrendous amount of partial application and (worse) a huge space leak. For example: f :: Eq a => [a] -> [a] f xs = ...f... If we don't take care, after typechecking we get f = /\a -> \d::Eq a -> let f' = f a d in \ys:[a] -> ...f'... Notice the the stupid construction of (f a d), which is of course identical to the function we're executing. In this case, the polymorphic recursion isn't being used (but that's a very common case). This can lead to a massive space leak, from the following top-level defn (post-typechecking) ff :: [Int] -> [Int] ff = f Int dEqInt Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but f' is another thunk which evaluates to the same thing... and you end up with a chain of identical values all hung onto by the CAF ff. ff = f Int dEqInt = let f' = f Int dEqInt in \ys. ...f'... = let f' = let f' = f Int dEqInt in \ys. ...f'... in \ys. ...f'... Etc. NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...), which would make the space leak go away in this case Solution: when typechecking the RHSs we always have in hand the *monomorphic* Ids for each binding. So we just need to make sure that if (Method f a d) shows up in the constraints emerging from (...f...) we just use the monomorphic Id. We achieve this by adding monomorphic Ids to the "givens" when simplifying constraints. That's what the "lies_avail" is doing. Then we get f = /\a -> \d::Eq a -> letrec fm = \ys:[a] -> ...fm... in fm  Austin Seipp committed Dec 03, 2014 158 -}  Simon Peyton Jones committed Mar 02, 2012 159   Simon Peyton Jones committed Nov 29, 2011 160 161 162 163 tcTopBinds :: HsValBinds Name -> TcM (TcGblEnv, TcLclEnv) -- The TcGblEnv contains the new tcg_binds and tcg_spects -- The TcLclEnv has an extended type envt for the new bindings tcTopBinds (ValBindsOut binds sigs)  cactus committed Jan 20, 2014 164 165 166 167 168  = do { -- Pattern synonym bindings populate the global environment (binds', (tcg_env, tcl_env)) <- tcValBinds TopLevel binds sigs $do { gbl <- getGblEnv ; lcl <- getLclEnv ; return (gbl, lcl) }  Simon Peyton Jones committed Nov 29, 2011 169 170 171 172 173 174 175 176  ; specs <- tcImpPrags sigs -- SPECIALISE prags for imported Ids ; let { tcg_env' = tcg_env { tcg_binds = foldr (unionBags . snd) (tcg_binds tcg_env) binds' , tcg_imp_specs = specs ++ tcg_imp_specs tcg_env } } ; return (tcg_env', tcl_env) }  cactus committed Nov 20, 2014 177  -- The top level bindings are flattened into a giant  Ian Lynagh committed May 18, 2008 178  -- implicitly-mutually-recursive LHsBinds  cactus committed Jan 20, 2014 179   Simon Peyton Jones committed Nov 29, 2011 180 181 182 183 184 185 tcTopBinds (ValBindsIn {}) = panic "tcTopBinds" tcRecSelBinds :: HsValBinds Name -> TcM TcGblEnv tcRecSelBinds (ValBindsOut binds sigs) = tcExtendGlobalValEnv [sel_id | L _ (IdSig sel_id) <- sigs]$ do { (rec_sel_binds, tcg_env) <- discardWarnings (tcValBinds TopLevel binds sigs getGblEnv)  cactus committed Nov 20, 2014 186  ; let tcg_env'  Edward Z. Yang committed Oct 24, 2014 187  | isHsBootOrSig (tcg_src tcg_env) = tcg_env  Simon Peyton Jones committed Nov 29, 2011 188 189 190  | otherwise = tcg_env { tcg_binds = foldr (unionBags . snd) (tcg_binds tcg_env) rec_sel_binds }  cactus committed Nov 20, 2014 191  -- Do not add the code for record-selector bindings when  Simon Peyton Jones committed Nov 29, 2011 192 193 194  -- compiling hs-boot files ; return tcg_env' } tcRecSelBinds (ValBindsIn {}) = panic "tcRecSelBinds"  simonpj committed Oct 13, 2000 195   simonpj committed Jul 19, 2005 196 tcHsBootSigs :: HsValBinds Name -> TcM [Id]  simonpj committed Jan 27, 2005 197 198 -- A hs-boot file has only one BindGroup, and it only has type -- signatures in it. The renamer checked all this  simonpj committed Aug 11, 2005 199 tcHsBootSigs (ValBindsOut binds sigs)  Ian Lynagh committed May 18, 2008 200  = do { checkTc (null binds) badBootDeclErr  waern committed Jun 10, 2011 201  ; concat <$> mapM (addLocM tc_boot_sig) (filter isTypeLSig sigs) }  simonpj committed Jan 27, 2005 202  where  thomasw committed Nov 28, 2014 203  tc_boot_sig (TypeSig lnames ty _) = mapM f lnames  waern committed Jun 10, 2011 204  where  Simon Peyton Jones committed Jan 06, 2015 205  f (L _ name) = do { sigma_ty <- tcHsSigType (FunSigCtxt name True) ty  waern committed Jun 10, 2011 206  ; return (mkVanillaGlobal name sigma_ty) }  Ian Lynagh committed May 18, 2008 207  -- Notice that we make GlobalIds, not LocalIds  Ian Lynagh committed May 18, 2008 208  tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)  simonpj committed Jul 12, 2005 209 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)  simonpj committed Oct 13, 2000 210   Simon Peyton Jones committed Jan 12, 2012 211 badBootDeclErr :: MsgDoc  Ian Lynagh committed Apr 12, 2008 212 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")  simonpj committed May 03, 2005 213   simonpj committed Jul 19, 2005 214 215 ------------------------ tcLocalBinds :: HsLocalBinds Name -> TcM thing  Ian Lynagh committed May 18, 2008 216  -> TcM (HsLocalBinds TcId, thing)  sof committed May 18, 1997 217   cactus committed Nov 20, 2014 218 tcLocalBinds EmptyLocalBinds thing_inside  Ian Lynagh committed May 18, 2008 219 220  = do { thing <- thing_inside ; return (EmptyLocalBinds, thing) }  sof committed May 18, 1997 221   Simon Peyton Jones committed Nov 29, 2011 222 223 224 225 tcLocalBinds (HsValBinds (ValBindsOut binds sigs)) thing_inside = do { (binds', thing) <- tcValBinds NotTopLevel binds sigs thing_inside ; return (HsValBinds (ValBindsOut binds' sigs), thing) } tcLocalBinds (HsValBinds (ValBindsIn {})) _ = panic "tcLocalBinds"  simonm committed Jan 08, 1998 226   simonpj committed Jul 19, 2005 227 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside  Simon Peyton Jones committed Jun 13, 2012 228 229 230  = do { ipClass <- tcLookupClass ipClassName ; (given_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM (tc_ip_bind ipClass)) ip_binds  simonpj committed Oct 23, 2002 231   cactus committed Nov 20, 2014 232  -- If the binding binds ?x = E, we must now  Ian Lynagh committed May 18, 2008 233  -- discharge any ?x constraints in expr_lie  simonpj@microsoft.com committed Oct 21, 2010 234  -- See Note [Implicit parameter untouchables]  cactus committed Nov 20, 2014 235  ; (ev_binds, result) <- checkConstraints (IPSkol ips)  simonpj@microsoft.com committed Oct 21, 2010 236  [] given_ips thing_inside  simonpj@microsoft.com committed Sep 13, 2010 237 238  ; return (HsIPBinds (IPBinds ip_binds' ev_binds), result) }  simonpj committed Oct 23, 2002 239  where  Simon Peyton Jones committed Jun 13, 2012 240  ips = [ip | L _ (IPBind (Left ip) _) <- ip_binds]  simonpj@microsoft.com committed Sep 13, 2010 241   Ian Lynagh committed May 18, 2008 242 243 244  -- I wonder if we should do these one at at time -- Consider ?x = 4 -- ?y = ?x + 1  Simon Peyton Jones committed Jun 13, 2012 245  tc_ip_bind ipClass (IPBind (Left ip) expr)  batterseapower committed May 15, 2012 246  = do { ty <- newFlexiTyVarTy openTypeKind  Simon Peyton Jones committed Jun 13, 2012 247 248  ; let p = mkStrLitTy$ hsIPNameFS ip ; ip_id <- newDict ipClass [ p, ty ]  simonpj@microsoft.com committed Sep 13, 2010 249  ; expr' <- tcMonoExpr expr ty  Simon Peyton Jones committed Jun 13, 2012 250 251 252 253 254 255 256 257  ; let d = toDict ipClass p ty fmap expr' ; return (ip_id, (IPBind (Right ip_id) d)) } tc_ip_bind _ (IPBind (Right {}) _) = panic "tc_ip_bind" -- Coerces a t into a dictionry for IP "x" t. -- co : t -> IP "x" t toDict ipClass x ty = case unwrapNewTyCon_maybe (classTyCon ipClass) of  Joachim Breitner committed Nov 27, 2013 258  Just (_,_,ax) -> HsWrap $mkWpCast$ mkTcSymCo $mkTcUnbranchedAxInstCo Representational ax [x,ty]  Simon Peyton Jones committed Jun 13, 2012 259 260  Nothing -> panic "The dictionary for IP is not a newtype?"  Austin Seipp committed Dec 03, 2014 261 {-  simonpj@microsoft.com committed Sep 17, 2010 262 263 264 265 266 267 268 Note [Implicit parameter untouchables] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We add the type variables in the types of the implicit parameters as untouchables, not so much because we really must not unify them, but rather because we otherwise end up with constraints like this Num alpha, Implic { wanted = alpha ~ Int } The constraint solver solves alpha~Int by unification, but then  cactus committed Nov 20, 2014 269 doesn't float that solved constraint out (it's not an unsolved  Simon Peyton Jones committed Aug 16, 2011 270 wanted). Result disaster: the (Num alpha) is again solved, this  simonpj@microsoft.com committed Sep 17, 2010 271 272 time by defaulting. No no no.  cactus committed Nov 20, 2014 273 However [Oct 10] this is all handled automatically by the  simonpj@microsoft.com committed Oct 21, 2010 274 275 untouchable-range idea.  Simon Peyton Jones committed Jun 24, 2014 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 Note [Placeholder PatSyn kinds] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this (Trac #9161) {-# LANGUAGE PatternSynonyms, DataKinds #-} pattern A = () b :: A b = undefined Here, the type signature for b mentions A. But A is a pattern synonym, which is typechecked (for very good reasons; a view pattern in the RHS may mention a value binding) as part of a group of bindings. It is entirely resonable to reject this, but to do so we need A to be in the kind environment when kind-checking the signature for B. Hence the tcExtendKindEnv2 patsyn_placeholder_kinds, which adds a binding A -> AGlobal (AConLike (PatSynCon _|_)) to the environment. Then TcHsType.tcTyVar will find A in the kind environment, and will give a 'wrongThingErr' as a result. But the lookup of A won't fail. The _|_ (= panic "fakePatSynCon") works because the wrongThingErr call, in tcTyVar, doesn't look inside the TcTyThing.  Austin Seipp committed Dec 03, 2014 298 -}  Simon Peyton Jones committed Jun 24, 2014 299   cactus committed Nov 20, 2014 300 tcValBinds :: TopLevelFlag  Simon Peyton Jones committed Nov 29, 2011 301 302  -> [(RecFlag, LHsBinds Name)] -> [LSig Name] -> TcM thing  cactus committed Nov 20, 2014 303  -> TcM ([(RecFlag, LHsBinds TcId)], thing)  simonpj committed Oct 27, 2005 304   Simon Peyton Jones committed Nov 29, 2011 305 tcValBinds top_lvl binds sigs thing_inside  Simon Peyton Jones committed Jun 24, 2014 306  = do { -- Typecheck the signature  thomasw committed Nov 28, 2014 307 308 309  ; (poly_ids, sig_fn, nwc_tvs) <- tcExtendKindEnv2 patsyn_placeholder_kinds$ -- See Note [Placeholder PatSyn kinds] tcTySigs sigs  Ian Lynagh committed May 18, 2008 310   Simon Peyton Jones committed Mar 02, 2012 311  ; let prag_fn = mkPragFun sigs (foldr (unionBags . snd) emptyBag binds)  Ian Lynagh committed May 18, 2008 312   cactus committed Nov 20, 2014 313  -- Extend the envt right away with all  Ian Lynagh committed May 18, 2008 314  -- the Ids declared with type signatures  thomasw committed Nov 28, 2014 315 316  -- Use tcExtendIdEnv3 to avoid extending the TcIdBinder stack ; tcExtendIdEnv3 [(idName id, id) | id <- poly_ids] (mkVarSet nwc_tvs) $do  cactus committed Jul 29, 2014 317 318  { (binds', (extra_binds', thing)) <- tcBindGroups top_lvl sig_fn prag_fn binds$ do { thing <- thing_inside  cactus committed Jul 29, 2014 319  -- See Note [Pattern synonym wrappers don't yield dependencies]  Simon Peyton Jones committed Nov 21, 2014 320  ; patsyn_workers <- mapM tcPatSynBuilderBind patsyns  cactus committed Nov 13, 2014 321  ; let extra_binds = [ (NonRecursive, worker) | worker <- patsyn_workers ]  cactus committed Jul 29, 2014 322 323  ; return (extra_binds, thing) } ; return (binds' ++ extra_binds', thing) }}  cactus committed Jun 21, 2014 324  where  cactus committed Jul 29, 2014 325 326  patsyns = [psb | (_, lbinds) <- binds, L _ (PatSynBind psb) <- bagToList lbinds]  Simon Peyton Jones committed Jun 24, 2014 327  patsyn_placeholder_kinds -- See Note [Placeholder PatSyn kinds]  cactus committed Jul 29, 2014 328  = [(name, placeholder_patsyn_tything)| PSB{ psb_id = L _ name } <- patsyns ]  Simon Peyton Jones committed Jun 24, 2014 329  placeholder_patsyn_tything  cactus committed Jul 29, 2014 330  = AGlobal $AConLike$ PatSynCon $panic "fakePatSynCon"  simonpj committed Mar 14, 1997 331   simonpj committed Jul 19, 2005 332 ------------------------  Simon Peyton Jones committed Mar 02, 2012 333 tcBindGroups :: TopLevelFlag -> TcSigFun -> PragFun  Ian Lynagh committed May 18, 2008 334 335  -> [(RecFlag, LHsBinds Name)] -> TcM thing -> TcM ([(RecFlag, LHsBinds TcId)], thing)  simonpj committed Jul 19, 2005 336 337 -- Typecheck a whole lot of value bindings, -- one strongly-connected component at a time  338 -- Here a "strongly connected component" has the strightforward  cactus committed Nov 20, 2014 339 -- meaning of a group of bindings that mention each other,  340 -- ignoring type signatures (that part comes later)  simonpj committed Jul 19, 2005 341   simonpj@microsoft.com committed Sep 13, 2010 342 tcBindGroups _ _ _ [] thing_inside  Ian Lynagh committed May 18, 2008 343 344  = do { thing <- thing_inside ; return ([], thing) }  simonpj committed Jul 19, 2005 345   simonpj@microsoft.com committed Sep 13, 2010 346 tcBindGroups top_lvl sig_fn prag_fn (group : groups) thing_inside  Ian Lynagh committed May 18, 2008 347  = do { (group', (groups', thing))  cactus committed Nov 20, 2014 348  <- tc_group top_lvl sig_fn prag_fn group$  simonpj@microsoft.com committed Sep 13, 2010 349  tcBindGroups top_lvl sig_fn prag_fn groups thing_inside  Ian Lynagh committed May 18, 2008 350  ; return (group' ++ groups', thing) }  sof committed May 18, 1997 351   simonpj committed Jul 19, 2005 352 ------------------------  cactus committed Nov 20, 2014 353 tc_group :: forall thing.  Simon Peyton Jones committed Mar 02, 2012 354  TopLevelFlag -> TcSigFun -> PragFun  Ian Lynagh committed May 18, 2008 355 356  -> (RecFlag, LHsBinds Name) -> TcM thing -> TcM ([(RecFlag, LHsBinds TcId)], thing)  simonpj committed Jul 19, 2005 357 358  -- Typecheck one strongly-connected component of the original program.  cactus committed Nov 20, 2014 359 -- We get a list of groups back, because there may  simonpj committed Jul 19, 2005 360 361 -- be specialisations etc as well  simonpj@microsoft.com committed Sep 13, 2010 362 tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside  Ian Lynagh committed May 18, 2008 363 364  -- A single non-recursive binding -- We want to keep non-recursive things non-recursive  simonpj committed Jul 19, 2005 365  -- so that we desugar unlifted bindings correctly  cactus committed Jan 20, 2014 366 367  = do { let bind = case bagToList binds of [bind] -> bind  cactus committed Jan 09, 2015 368 369  [] -> panic "tc_group: empty list of binds" _ -> panic "tc_group: NonRecursive binds is not a singleton bag"  cactus committed Jan 20, 2014 370 371  ; (bind', thing) <- tc_single top_lvl sig_fn prag_fn bind thing_inside ; return ( [(NonRecursive, bind')], thing) }  simonpj@microsoft.com committed Sep 13, 2010 372 373  tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside  cactus committed Nov 20, 2014 374 375  = -- To maximise polymorphism, we do a new -- strongly-connected-component analysis, this time omitting  Ian Lynagh committed May 18, 2008 376  -- any references to variables with type signatures.  377  -- (This used to be optional, but isn't now.)  simonpj@microsoft.com committed Sep 13, 2010 378  do { traceTc "tc_group rec" (pprLHsBinds binds)  cactus committed Jan 20, 2014 379  ; when hasPatSyn $recursivePatSynErr binds  cactus committed Jan 09, 2015 380  ; (binds1, thing) <- go sccs  simonpj@microsoft.com committed Sep 13, 2010 381  ; return ([(Recursive, binds1)], thing) }  Ian Lynagh committed May 18, 2008 382  -- Rec them all together  simonpj committed Jul 19, 2005 383  where  cactus committed Apr 13, 2014 384  hasPatSyn = anyBag (isPatSyn . unLoc) binds  cactus committed Jan 20, 2014 385 386 387  isPatSyn PatSynBind{} = True isPatSyn _ = False  cactus committed Apr 13, 2014 388  sccs :: [SCC (LHsBind Name)]  simonpj@microsoft.com committed Sep 13, 2010 389 390  sccs = stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds)  cactus committed Jan 09, 2015 391  go :: [SCC (LHsBind Name)] -> TcM (LHsBinds TcId, thing)  Simon Peyton Jones committed Aug 16, 2011 392  go (scc:sccs) = do { (binds1, ids1, closed) <- tc_scc scc  cactus committed Jan 09, 2015 393 394 395 396  ; (binds2, thing) <- tcExtendLetEnv top_lvl closed ids1$ go sccs ; return (binds1 unionBags binds2, thing) } go [] = do { thing <- thing_inside; return (emptyBag, thing) }  simonpj committed Jul 22, 2005 397   simonpj@microsoft.com committed Sep 13, 2010 398 399  tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive [bind] tc_scc (CyclicSCC binds) = tc_sub_group Recursive binds  sof committed May 18, 1997 400   simonpj@microsoft.com committed Sep 05, 2006 401  tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive  sof committed May 18, 1997 402   cactus committed Jan 20, 2014 403 404 405 406 recursivePatSynErr :: OutputableBndr name => LHsBinds name -> TcM a recursivePatSynErr binds = failWithTc $hang (ptext (sLit "Recursive pattern synonym definition with following bindings:"))  cactus committed Apr 13, 2014 407  2 (vcat$ map pprLBind . bagToList $binds)  cactus committed Jan 20, 2014 408 409 410 411 412 413 414  where pprLoc loc = parens (ptext (sLit "defined at") <+> ppr loc) pprLBind (L loc bind) = pprWithCommas ppr (collectHsBindBinders bind) <+> pprLoc loc tc_single :: forall thing. TopLevelFlag -> TcSigFun -> PragFun  cactus committed Apr 13, 2014 415  -> LHsBind Name -> TcM thing  cactus committed Jan 20, 2014 416  -> TcM (LHsBinds TcId, thing)  cactus committed Nov 20, 2014 417 418 tc_single _top_lvl sig_fn _prag_fn (L _ (PatSynBind psb@PSB{ psb_id = L _ name })) thing_inside = do { (pat_syn, aux_binds) <- tc_pat_syn_decl  cactus committed Jan 20, 2014 419  ; let tything = AConLike (PatSynCon pat_syn)  cactus committed Jan 09, 2015 420  ; thing <- tcExtendGlobalEnv [tything] thing_inside  cactus committed Jan 20, 2014 421 422  ; return (aux_binds, thing) }  cactus committed Nov 20, 2014 423 424  where tc_pat_syn_decl = case sig_fn name of  cactus committed Jan 09, 2015 425  Nothing -> tcInferPatSynDecl psb  cactus committed Nov 20, 2014 426  Just (TcPatSynInfo tpsi) -> tcCheckPatSynDecl psb tpsi  cactus committed Jan 09, 2015 427  Just _ -> panic "tc_single"  cactus committed Nov 20, 2014 428   cactus committed Jan 20, 2014 429 430 431 432 433 434 tc_single top_lvl sig_fn prag_fn lbind thing_inside = do { (binds1, ids, closed) <- tcPolyBinds top_lvl sig_fn prag_fn NonRecursive NonRecursive [lbind] ; thing <- tcExtendLetEnv top_lvl closed ids thing_inside ; return (binds1, thing) }  cactus committed Nov 20, 2014 435   thomasw committed Nov 28, 2014 436 437 438 439 440 -- | No signature or a partial signature noCompleteSig :: Maybe TcSigInfo -> Bool noCompleteSig Nothing = True noCompleteSig (Just sig) = isPartialSig sig  simonpj committed Aug 10, 2005 441 ------------------------  cactus committed Jan 09, 2015 442 mkEdges :: TcSigFun -> LHsBinds Name -> [Node BKey (LHsBind Name)]  simonpj committed Aug 10, 2005 443   cactus committed Jan 09, 2015 444 type BKey = Int -- Just number off the bindings  simonpj committed Aug 10, 2005 445 446  mkEdges sig_fn binds  447  = [ (bind, key, [key | n <- nameSetElems (bind_fvs (unLoc bind)),  Ian Lynagh committed May 18, 2008 448  Just key <- [lookupNameEnv key_map n], no_sig n ])  simonpj committed Aug 10, 2005 449 450 451 452  | (bind, key) <- keyd_binds ] where no_sig :: Name -> Bool  thomasw committed Nov 28, 2014 453  no_sig n = noCompleteSig (sig_fn n)  simonpj committed Aug 10, 2005 454 455 456  keyd_binds = bagToList binds zip [0::BKey ..]  Ian Lynagh committed May 18, 2008 457  key_map :: NameEnv BKey -- Which binding it comes from  cactus committed Apr 13, 2014 458  key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds  cactus committed Jan 09, 2015 459  , bndr <- collectHsBindBinders bind ]  simonpj committed Mar 14, 1997 460   simonpj committed Jul 19, 2005 461 ------------------------  Simon Peyton Jones committed Mar 02, 2012 462 tcPolyBinds :: TopLevelFlag -> TcSigFun -> PragFun  cactus committed Jan 09, 2015 463 464 465 466  -> RecFlag -- Whether the group is really recursive -> RecFlag -- Whether it's recursive after breaking -- dependencies based on type signatures -> [LHsBind Name] -- None are PatSynBind  chak@cse.unsw.edu.au. committed Oct 31, 2011 467  -> TcM (LHsBinds TcId, [TcId], TopLevelFlag)  simonpj committed Jul 19, 2005 468   cactus committed Jan 09, 2015 469 -- Typechecks a single bunch of values bindings all together,  simonpj committed Jul 19, 2005 470 471 472 -- and generalises them. The bunch may be only part of a recursive -- group, because we use type signatures to maximise polymorphism --  simonpj committed Jul 22, 2005 473 474 -- Returns a list because the input may be a single non-recursive binding, -- in which case the dependency order of the resulting bindings is  cactus committed Nov 20, 2014 475 476 -- important. --  simonpj committed Jul 19, 2005 477 -- Knows nothing about the scope of the bindings  cactus committed Jan 09, 2015 478 -- None of the bindings are pattern synonyms  simonpj committed Jul 19, 2005 479   simonpj@microsoft.com committed Sep 13, 2010 480 481 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc bind_list = setSrcSpan loc$  cactus committed Nov 20, 2014 482  recoverM (recoveryCode binder_names sig_fn) $do  simonpj@microsoft.com committed Mar 31, 2011 483  -- Set up main recover; take advantage of any type sigs  simonpj committed Sep 30, 2004 484   Austin Seipp committed Sep 09, 2014 485  { traceTc "------------------------------------------------" Outputable.empty  Simon Peyton Jones committed May 09, 2012 486  ; traceTc "Bindings for {" (ppr binder_names)  Ian Lynagh committed Jan 19, 2012 487  ; dflags <- getDynFlags  Simon Peyton Jones committed Aug 16, 2011 488  ; type_env <- getLclTypeEnv  cactus committed Nov 20, 2014 489  ; let plan = decideGeneralisationPlan dflags type_env  Simon Peyton Jones committed Mar 02, 2012 490  binder_names bind_list sig_fn  simonpj@microsoft.com committed Sep 13, 2010 491  ; traceTc "Generalisation plan" (ppr plan)  Simon Peyton Jones committed May 09, 2012 492  ; result@(tc_binds, poly_ids, _) <- case plan of  cactus committed Jan 20, 2014 493 494 495  NoGen -> tcPolyNoGen rec_tc prag_fn sig_fn bind_list InferGen mn cl -> tcPolyInfer rec_tc prag_fn sig_fn mn cl bind_list CheckGen lbind sig -> tcPolyCheck rec_tc prag_fn sig lbind  simonpj@microsoft.com committed Sep 13, 2010 496   chak@cse.unsw.edu.au. committed Oct 31, 2011 497  -- Check whether strict bindings are ok  Ian Lynagh committed May 18, 2008 498 499  -- These must be non-recursive etc, and are not generalised -- They desugar to a case expression in the end  Simon Peyton Jones committed May 09, 2012 500 501 502 503  ; checkStrictBinds top_lvl rec_group bind_list tc_binds poly_ids ; traceTc "} End of bindings for" (vcat [ ppr binder_names, ppr rec_group , vcat [ppr id <+> ppr (idType id) | id <- poly_ids] ])  simonpj@microsoft.com committed Sep 13, 2010 504   Simon Peyton Jones committed Aug 16, 2011 505  ; return result }  simonpj@microsoft.com committed Sep 13, 2010 506  where  cactus committed Apr 13, 2014 507 508  binder_names = collectHsBindListBinders bind_list loc = foldr1 combineSrcSpans (map getLoc bind_list)  cactus committed Nov 20, 2014 509  -- The mbinds have been dependency analysed and  simonpj@microsoft.com committed Mar 31, 2011 510  -- may no longer be adjacent; so find the narrowest  chak@cse.unsw.edu.au. committed Oct 31, 2011 511  -- span that includes them all  simonpj@microsoft.com committed Sep 13, 2010 512   513 ------------------  Simon Peyton Jones committed Sep 17, 2012 514 tcPolyNoGen -- No generalisation whatsoever  Simon Peyton Jones committed Sep 10, 2013 515  :: RecFlag -- Whether it's recursive after breaking  simonpj@microsoft.com committed Sep 13, 2010 516  -- dependencies based on type signatures  Simon Peyton Jones committed Sep 17, 2012 517  -> PragFun -> TcSigFun  cactus committed Apr 13, 2014 518  -> [LHsBind Name]  Simon Peyton Jones committed Aug 16, 2011 519  -> TcM (LHsBinds TcId, [TcId], TopLevelFlag)  simonpj@microsoft.com committed Sep 13, 2010 520   Simon Peyton Jones committed Sep 10, 2013 521 522 tcPolyNoGen rec_tc prag_fn tc_sig_fn bind_list = do { (binds', mono_infos) <- tcMonoBinds rec_tc tc_sig_fn  cactus committed Nov 20, 2014 523  (LetGblBndr prag_fn)  Simon Peyton Jones committed Sep 17, 2012 524  bind_list  simonpj@microsoft.com committed Sep 13, 2010 525  ; mono_ids' <- mapM tc_mono_info mono_infos  Simon Peyton Jones committed Aug 16, 2011 526  ; return (binds', mono_ids', NotTopLevel) }  simonpj@microsoft.com committed Sep 13, 2010 527 528  where tc_mono_info (name, _, mono_id)  Simon Peyton Jones committed Feb 16, 2012 529  = do { mono_ty' <- zonkTcType (idType mono_id)  chak@cse.unsw.edu.au. committed Oct 31, 2011 530  -- Zonk, mainly to expose unboxed types to checkStrictBinds  simonpj@microsoft.com committed Sep 13, 2010 531  ; let mono_id' = setIdType mono_id mono_ty'  simonpj@microsoft.com committed Oct 07, 2010 532  ; _specs <- tcSpecPrags mono_id' (prag_fn name)  533  ; return mono_id' }  chak@cse.unsw.edu.au. committed Oct 31, 2011 534 535 536 537  -- NB: tcPrags generates error messages for -- specialisation pragmas for non-overloaded sigs -- Indeed that is why we call it here! -- So we can safely ignore _specs  simonpj@microsoft.com committed Sep 13, 2010 538 539  ------------------  Simon Peyton Jones committed Sep 10, 2013 540 tcPolyCheck :: RecFlag -- Whether it's recursive after breaking  chak@cse.unsw.edu.au. committed Oct 31, 2011 541  -- dependencies based on type signatures  Simon Peyton Jones committed Jan 06, 2015 542 543  -> PragFun -> TcSigInfo  cactus committed Apr 13, 2014 544  -> LHsBind Name  chak@cse.unsw.edu.au. committed Oct 31, 2011 545  -> TcM (LHsBinds TcId, [TcId], TopLevelFlag)  cactus committed Nov 20, 2014 546 -- There is just one binding,  simonpj@microsoft.com committed Sep 13, 2010 547 548 -- it binds a single variable, -- it has a signature,  Simon Peyton Jones committed Sep 10, 2013 549 tcPolyCheck rec_tc prag_fn  cactus committed Nov 20, 2014 550  sig@(TcSigInfo { sig_id = poly_id, sig_tvs = tvs_w_scoped  thomasw committed Nov 28, 2014 551  , sig_nwcs = sig_nwcs, sig_theta = theta  Simon Peyton Jones committed Jan 06, 2015 552 553  , sig_tau = tau, sig_loc = loc , sig_warn_redundant = warn_redundant })  cactus committed Apr 13, 2014 554  bind  thomasw committed Nov 28, 2014 555 556  = ASSERT( null sig_nwcs ) -- We should be in tcPolyInfer if there are wildcards do { ev_vars <- newEvVars theta  Simon Peyton Jones committed Jan 06, 2015 557 558  ; let ctxt = FunSigCtxt (idName poly_id) warn_redundant skol_info = SigSkol ctxt (mkPhiTy theta tau)  Simon Peyton Jones committed Aug 16, 2011 559  prag_sigs = prag_fn (idName poly_id)  Simon Peyton Jones committed Mar 07, 2014 560  tvs = map snd tvs_w_scoped  cactus committed Nov 20, 2014 561 562  ; (ev_binds, (binds', [mono_info])) <- setSrcSpan loc$  Simon Peyton Jones committed Mar 02, 2012 563  checkConstraints skol_info tvs ev_vars $ cactus committed Jan 20, 2014 564  tcMonoBinds rec_tc (\_ -> Just sig) LetLclBndr [bind]  simonpj@microsoft.com committed Sep 13, 2010 565   Simon Peyton Jones committed Aug 16, 2011 566 567  ; spec_prags <- tcSpecPrags poly_id prag_sigs ; poly_id <- addInlinePrags poly_id prag_sigs  simonpj@microsoft.com committed Sep 13, 2010 568   Simon Peyton Jones committed Aug 16, 2011 569 570 571 572 573  ; let (_, _, mono_id) = mono_info export = ABE { abe_wrap = idHsWrapper , abe_poly = poly_id , abe_mono = mono_id , abe_prags = SpecPrags spec_prags }  cactus committed Nov 20, 2014 574  abs_bind = L loc$ AbsBinds  simonpj@microsoft.com committed Sep 13, 2010 575  { abs_tvs = tvs  Simon Peyton Jones committed Jan 06, 2015 576  , abs_ev_vars = ev_vars, abs_ev_binds = [ev_binds]  simonpj@microsoft.com committed Sep 13, 2010 577  , abs_exports = [export], abs_binds = binds' }  Simon Peyton Jones committed Aug 16, 2011 578 579  closed | isEmptyVarSet (tyVarsOfType (idType poly_id)) = TopLevel | otherwise = NotTopLevel  cactus committed Apr 13, 2014 580  ; return (unitBag abs_bind, [poly_id], closed) }  simonpj@microsoft.com committed Sep 13, 2010 581   cactus committed Nov 20, 2014 582 583 584 tcPolyCheck _rec_tc _prag_fn sig _bind = pprPanic "tcPolyCheck" (ppr sig)  585 ------------------  cactus committed Nov 20, 2014 586 tcPolyInfer  Simon Peyton Jones committed Sep 10, 2013 587  :: RecFlag -- Whether it's recursive after breaking  simonpj@microsoft.com committed Sep 13, 2010 588  -- dependencies based on type signatures  cactus committed Nov 20, 2014 589  -> PragFun -> TcSigFun  Simon Peyton Jones committed Sep 17, 2012 590 591  -> Bool -- True <=> apply the monomorphism restriction -> Bool -- True <=> free vars have closed types  cactus committed Apr 13, 2014 592  -> [LHsBind Name]  Simon Peyton Jones committed Aug 16, 2011 593  -> TcM (LHsBinds TcId, [TcId], TopLevelFlag)  Simon Peyton Jones committed Sep 10, 2013 594 tcPolyInfer rec_tc prag_fn tc_sig_fn mono closed bind_list  Simon Peyton Jones committed Jan 06, 2015 595 596  = do { ((binds', mono_infos), tclvl, wanted) <- pushLevelAndCaptureConstraints $ Simon Peyton Jones committed Sep 10, 2013 597  tcMonoBinds rec_tc tc_sig_fn LetLclBndr bind_list  simonpj@microsoft.com committed Sep 13, 2010 598   simonpj@microsoft.com committed Jan 12, 2011 599  ; let name_taus = [(name, idType mono_id) | (name, _, mono_id) <- mono_infos]  Simon Peyton Jones committed May 22, 2013 600  ; traceTc "simplifyInfer call" (ppr name_taus $$ppr wanted)  Simon Peyton Jones committed Jun 11, 2014 601  ; (qtvs, givens, mr_bites, ev_binds)  Simon Peyton Jones committed Dec 02, 2014 602  <- simplifyInfer tclvl mono name_taus wanted  simonpj@microsoft.com committed Sep 13, 2010 603   thomasw committed Nov 28, 2014 604 605 606 607  ; inferred_theta <- zonkTcThetaType (map evVarPred givens) ; exports <- checkNoErrs mapM (mkExport prag_fn qtvs inferred_theta) mono_infos  simonpj@microsoft.com committed Sep 13, 2010 608  ; loc <- getSrcSpanM  Simon Peyton Jones committed Aug 16, 2011 609  ; let poly_ids = map abe_poly exports  chak@cse.unsw.edu.au. committed Oct 31, 2011 610 611  final_closed | closed && not mr_bites = TopLevel | otherwise = NotTopLevel  cactus committed Nov 20, 2014 612  abs_bind = L loc  Simon Peyton Jones committed Aug 16, 2011 613  AbsBinds { abs_tvs = qtvs  Simon Peyton Jones committed Jan 06, 2015 614  , abs_ev_vars = givens, abs_ev_binds = [ev_binds]  Simon Peyton Jones committed Aug 16, 2011 615  , abs_exports = exports, abs_binds = binds' }  simonpj@microsoft.com committed Sep 13, 2010 616   Simon Peyton Jones committed Sep 01, 2011 617 618  ; traceTc "Binding:" (ppr final_closed$$ ppr (poly_ids zip map idType poly_ids))  cactus committed Apr 13, 2014 619  ; return (unitBag abs_bind, poly_ids, final_closed) }  Simon Peyton Jones committed Aug 16, 2011 620  -- poly_ids are guaranteed zonked by mkExport  simonpj committed Jul 19, 2005 621 622  --------------  Simon Peyton Jones committed Oct 03, 2013 623 mkExport :: PragFun  chak@cse.unsw.edu.au. committed Oct 31, 2011 624  -> [TyVar] -> TcThetaType -- Both already zonked  Ian Lynagh committed May 18, 2008 625  -> MonoBindInfo  Simon Peyton Jones committed Aug 16, 2011 626  -> TcM (ABExport Id)  Simon Peyton Jones committed Oct 03, 2013 627 628 629 630 -- Only called for generalisation plan IferGen, not by CheckGen or NoGen -- -- mkExport generates exports with -- zonked type variables,  Ian Lynagh committed May 18, 2008 631 -- zonked poly_ids  simonpj@microsoft.com committed Sep 18, 2006 632 633 634 635 -- The former is just because no further unifications will change -- the quantified type variables, so we can fix their final form -- right now. -- The latter is needed because the poly_ids are used to extend the  Simon Peyton Jones committed Oct 03, 2013 636 -- type environment; see the invariant on TcEnv.tcExtendIdEnv  simonpj@microsoft.com committed Sep 18, 2006 637   Simon Peyton Jones committed Aug 16, 2011 638 -- Pre-condition: the qtvs and theta are already zonked  simonpj@microsoft.com committed Sep 18, 2006 639   thomasw committed Nov 28, 2014 640 mkExport prag_fn qtvs inferred_theta (poly_name, mb_sig, mono_id)  Simon Peyton Jones committed Feb 16, 2012 641  = do { mono_ty <- zonkTcType (idType mono_id)  642   Simon Peyton Jones committed Jun 11, 2014 643  ; poly_id <- case mb_sig of  thomasw committed Nov 28, 2014 644 645 646 647 648 649 650  Nothing -> mkInferredPolyId poly_name qtvs inferred_theta mono_ty Just (TcPatSynInfo _) -> panic "mkExport" Just sig | isPartialSig sig -> do { final_theta <- completeTheta inferred_theta sig ; mkInferredPolyId poly_name qtvs final_theta mono_ty } | otherwise -> return (sig_id sig)  Simon Peyton Jones committed Jun 11, 2014 651 652  -- NB: poly_id has a zonked type  Simon Peyton Jones committed Aug 16, 2011 653  ; poly_id <- addInlinePrags poly_id prag_sigs  simonpj@microsoft.com committed Oct 07, 2010 654  ; spec_prags <- tcSpecPrags poly_id prag_sigs  Ian Lynagh committed May 18, 2008 655  -- tcPrags requires a zonked poly_id  simonpj@microsoft.com committed Sep 18, 2006 656   thomasw committed Nov 28, 2014 657  ; let sel_poly_ty = mkSigmaTy qtvs inferred_theta mono_ty  Simon Peyton Jones committed Oct 03, 2013 658  ; traceTc "mkExport: check sig"  thomasw committed Nov 28, 2014 659  (vcat [ ppr poly_name, ppr sel_poly_ty, ppr (idType poly_id) ])  Simon Peyton Jones committed Aug 16, 2011 660   chak@cse.unsw.edu.au. committed Oct 31, 2011 661 662 663  -- Perform the impedence-matching and ambiguity check -- right away. If it fails, we want to fail now (and recover -- in tcPolyBinds). If we delay checking, we get an error cascade.  Simon Peyton Jones committed Oct 03, 2013 664  -- Remember we are in the tcPolyInfer case, so the type envt is  chak@cse.unsw.edu.au. committed Oct 31, 2011 665 666  -- closed (unless we are doing NoMonoLocalBinds in which case all bets -- are off)  667  -- See Note [Impedence matching]  Simon Peyton Jones committed Jun 11, 2014 668  ; (wrap, wanted) <- addErrCtxtM (mk_bind_msg inferred True poly_name (idType poly_id))$  Simon Peyton Jones committed Aug 16, 2011 669  captureConstraints $ Simon Peyton Jones committed Nov 21, 2014 670  tcSubType_NC sig_ctxt sel_poly_ty (idType poly_id)  Simon Peyton Jones committed Oct 03, 2013 671  ; ev_binds <- simplifyTop wanted  Simon Peyton Jones committed Aug 16, 2011 672 673 674 675 676  ; return (ABE { abe_wrap = mkWpLet (EvBinds ev_binds) <.> wrap , abe_poly = poly_id , abe_mono = mono_id , abe_prags = SpecPrags spec_prags }) }  simonpj@microsoft.com committed Sep 18, 2006 677  where  Simon Peyton Jones committed Aug 16, 2011 678 679 680  inferred = isNothing mb_sig prag_sigs = prag_fn poly_name sig_ctxt = InfSigCtxt poly_name  Simon Peyton Jones committed Jun 11, 2014 681 682 683 684 685 686  mkInferredPolyId :: Name -> [TyVar] -> TcThetaType -> TcType -> TcM Id -- In the inference case (no signature) this stuff figures out -- the right type variables and theta to quantify over -- See Note [Validity of inferred types] mkInferredPolyId poly_name qtvs theta mono_ty  Simon Peyton Jones committed Nov 04, 2014 687 688 689  = do { fam_envs <- tcGetFamInstEnvs ; let (_co, norm_mono_ty) = normaliseType fam_envs Nominal mono_ty  Simon Peyton Jones committed Nov 06, 2014 690 691  -- Unification may not have normalised the type, -- (see Note [Lazy flattening] in TcFlatten) so do it  Simon Peyton Jones committed Nov 04, 2014 692 693 694  -- here to make it as uncomplicated as possible. -- Example: f :: [F Int] -> Bool -- should be rewritten to f :: [Char] -> Bool, if possible  Simon Peyton Jones committed Nov 06, 2014 695   Simon Peyton Jones committed Nov 04, 2014 696  my_tvs2 = closeOverKinds (growThetaTyVars theta (tyVarsOfType norm_mono_ty))  Simon Peyton Jones committed Jun 11, 2014 697  -- Include kind variables! Trac #7916  Simon Peyton Jones committed Nov 06, 2014 698   Simon Peyton Jones committed Nov 04, 2014 699 700 701 702 703 704  my_tvs = filter (elemVarSet my_tvs2) qtvs -- Maintain original order my_theta = filter (quantifyPred my_tvs2) theta inferred_poly_ty = mkSigmaTy my_tvs my_theta norm_mono_ty ; addErrCtxtM (mk_bind_msg True False poly_name inferred_poly_ty)$ checkValidType (InfSigCtxt poly_name) inferred_poly_ty  Simon Peyton Jones committed Nov 21, 2014 705   Simon Peyton Jones committed Nov 04, 2014 706  ; return (mkLocalId poly_name inferred_poly_ty) }  Simon Peyton Jones committed Jun 11, 2014 707 708 709  mk_bind_msg :: Bool -> Bool -> Name -> TcType -> TidyEnv -> TcM (TidyEnv, SDoc) mk_bind_msg inferred want_ambig poly_name poly_ty tidy_env  Simon Peyton Jones committed Nov 21, 2014 710 711  = do { (tidy_env', tidy_ty) <- zonkTidyTcType tidy_env poly_ty ; return (tidy_env', mk_msg tidy_ty) }  Simon Peyton Jones committed Jun 11, 2014 712  where  Simon Peyton Jones committed Nov 21, 2014 713 714 715 716 717  mk_msg ty = vcat [ ptext (sLit "When checking that") <+> quotes (ppr poly_name) <+> ptext (sLit "has the") <+> what <+> ptext (sLit "type") , nest 2 (ppr poly_name <+> dcolon <+> ppr ty) , ppWhen want_ambig \$ ptext (sLit "Probable cause: the inferred type is ambiguous") ]  Simon Peyton Jones committed Jun 11, 2014 718 719  what | inferred = ptext (sLit "inferred") | otherwise = ptext (sLit "specified")  thomasw committed Nov 28, 2014 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740  -- | Report the inferred constraints for an extra-constraints wildcard/hole as -- an error message, unless the PartialTypeSignatures flag is enabled. In this -- case, the extra inferred constraints are accepted without complaining. -- Returns the annotated constraints combined with the inferred constraints. completeTheta :: TcThetaType -> TcSigInfo -> TcM TcThetaType completeTheta _ (TcPatSynInfo _) = panic "Extra-constraints wildcard not supported in a pattern signature" completeTheta inferred_theta sig@(TcSigInfo { sig_id = poly_id , sig_extra_cts = mb_extra_cts , sig_theta = annotated_theta }) | Just loc <- mb_extra_cts = do { annotated_theta <- zonkTcThetaType annotated_theta ; let inferred_diff = minusList inferred_theta annotated_theta final_theta = annotated_theta ++ inferred_diff ; partial_sigs <- xoptM Opt_PartialTypeSignatures ; warn_partial_sigs <- woptM Opt_WarnPartialTypeSignatures ; msg <- mkLongErrAt loc (mk_msg inferred_diff partial_sigs) empty ; case partial_sigs of  Simon Peyton Jones committed Jan 09, 2015 741  True | warn_partial_sigs -> reportWarning msg  thomasw committed Nov 28, 2014 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758  | otherwise -> return () False -> reportError msg ; return final_theta } | otherwise = zonkTcThetaType annotated_theta -- No extra-constraints wildcard means no extra constraints will be added -- to the context, so just return the possibly empty (zonked) -- annotated_theta. where pts_hint = text "To use the inferred type, enable PartialTypeSignatures" mk_msg inferred_diff suppress_hint = vcat [ hang ((text "Found hole") <+> quotes (char '_')) 2 (text "with inferred constraints:") <+> pprTheta inferred_diff , if suppress_hint then empty else pts_hint , typeSigCtxt (idName poly_id) sig ]  simonpj committed Jul 19, 2005 759   Austin Seipp committed Dec 03, 2014 760 {-  Simon Peyton Jones committed Jan 06, 2015 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 Note [Partial type signatures and generalisation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When we have a partial type signature, like f :: _ -> Int then we *always* use the InferGen plan, and hence tcPolyInfer. We do this even for a local binding with -XMonoLocalBinds. Reasons: * The TcSigInfo for 'f' has a unification variable for the '_', whose TcLevel is one level deeper than the current level. (See pushTcLevelM in tcTySig.) But NoGen doesn't increase the TcLevel like InferGen, so we lose the level invariant. * The signature might be f :: forall a. _ -> a so it really is polymorphic. It's not clear what it would mean to use NoGen on this, and indeed the ASSERT in tcLhs, in the (Just sig) case, checks that if there is a signature then we are using LetLclBndr, and hence a nested AbsBinds with increased TcLevel It might be possible to fix these difficulties somehow, but there doesn't seem much point. Indeed, adding a partial type signature is a way to get per-binding inferred generalisation.  Simon Peyton Jones committed Jun 11, 2014 784 785 Note [Validity of inferred types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  cactus committed Nov 20, 2014 786 We need to check inferred type for validity, in case it uses language  Simon Peyton Jones committed Jun 11, 2014 787 788 789 790 791 792 793 794 795 796 extensions that are not turned on. The principle is that if the user simply adds the inferred type to the program source, it'll compile fine. See #8883. Examples that might fail: - an inferred theta that requires type equalities e.g. (F a ~ G b) or multi-parameter type classes - an inferred type that includes unboxed tuples However we don't do the ambiguity check (checkValidType omits it for  cactus committed Nov 20, 2014 797 InfSigCtxt) because the impedence-matching stage, which follows  Simon Peyton Jones committed Jun 11, 2014 798 799 800 801 802 immediately, will do it and we don't want two error messages. Moreover, because of the impedence matching stage, the ambiguity-check suggestion of -XAllowAmbiguiousTypes will not work.  803 804 805 806 807 808 809 810 811 812 Note [Impedence matching] ~~~~~~~~~~~~~~~~~~~~~~~~~ Consider f 0 x = x f n x = g [] (not x) g [] y = f 10 y g _ y = f 9 y After typechecking we'll get  cactus committed Nov 20, 2014 813 814  f_mono_ty :: a -> Bool -> Bool g_mono_ty :: [b] -> Bool -> Bool  815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 with constraints (Eq a, Num a) Note that f is polymorphic in 'a' and g in 'b'; and these are not linked. The types we really want for f and g are f :: forall a. (Eq a, Num a) => a -> Bool -> Bool g :: forall b. [b] -> Bool -> Bool We can get these by "impedence matching": tuple :: forall a b. (Eq a, Num a) => (a -> Bool -> Bool, [b] -> Bool -> Bool) tuple a b d1 d1 = let ...bind f_mono, g_mono in (f_mono, g_mono) f a d1 d2 = case tuple a Any d1 d2 of (f, g) -> f g b = case tuple Integer b dEqInteger dNumInteger of (f,g) -> g Suppose the shared quantified tyvars are qtvs and constraints theta.  cactus committed Nov 20, 2014 831 Then we want to check that  832  f's polytype is more polymorphic than forall qtvs. theta => f_mono_ty  cactus committed Nov 20, 2014 833 and the proof is the impedence matcher.  834 835 836 837 838 839  Notice that the impedence matcher may do defaulting. See Trac #7173. It also cleverly does an ambiguity check; for example, rejecting f :: F a -> a where F is a non-injective type function.  Austin Seipp committed Dec 03, 2014 840 -}  841   Simon Peyton Jones committed Jan 14, 2015 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915