MkCore.lhs 22.9 KB
 batterseapower committed Jul 31, 2008 1 2 3 4 5 6 7 8 9 \begin{code} -- | Handy functions for creating much Core syntax module MkCore ( -- * Constructing normal syntax mkCoreLet, mkCoreLets, mkCoreApp, mkCoreApps, mkCoreConApps, mkCoreLams, -- * Constructing boxed literals  batterseapower committed Aug 07, 2008 10 11 12  mkWordExpr, mkWordExprWord, mkIntExpr, mkIntExprInt, mkIntegerExpr,  batterseapower committed Jul 31, 2008 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128  mkFloatExpr, mkDoubleExpr, mkCharExpr, mkStringExpr, mkStringExprFS, -- * Constructing general big tuples -- $big_tuples mkChunkified, -- * Constructing small tuples mkCoreVarTup, mkCoreVarTupTy, mkCoreTup, mkCoreTupTy, -- * Constructing big tuples mkBigCoreVarTup, mkBigCoreVarTupTy, mkBigCoreTup, mkBigCoreTupTy, -- * Deconstructing small tuples mkSmallTupleSelector, mkSmallTupleCase, -- * Deconstructing big tuples mkTupleSelector, mkTupleCase, -- * Constructing list expressions mkNilExpr, mkConsExpr, mkListExpr, mkFoldrExpr, mkBuildExpr ) where #include "HsVersions.h" import Id import Var ( setTyVarUnique ) import CoreSyn import CoreUtils ( exprType, needsCaseBinding, bindNonRec ) import Literal import HscTypes import TysWiredIn import PrelNames import MkId ( seqId ) import Type import TypeRep import TysPrim ( alphaTyVar ) import DataCon ( DataCon, dataConWorkId ) import FastString import UniqSupply import BasicTypes import Util ( notNull, zipEqual ) import Panic import Constants import Data.Char ( ord ) import Data.Word infixl 4 mkCoreApp, mkCoreApps \end{code} %************************************************************************ %* * \subsection{Basic CoreSyn construction} %* * %************************************************************************ \begin{code} -- | Bind a binding group over an expression, using a @let@ or @case@ as -- appropriate (see "CoreSyn#let_app_invariant") mkCoreLet :: CoreBind -> CoreExpr -> CoreExpr mkCoreLet (NonRec bndr rhs) body -- See Note [CoreSyn let/app invariant] | needsCaseBinding (idType bndr) rhs = Case rhs bndr (exprType body) [(DEFAULT,[],body)] mkCoreLet bind body = Let bind body -- | Bind a list of binding groups over an expression. The leftmost binding -- group becomes the outermost group in the resulting expression mkCoreLets :: [CoreBind] -> CoreExpr -> CoreExpr mkCoreLets binds body = foldr mkCoreLet body binds -- | Construct an expression which represents the application of one expression -- to the other mkCoreApp :: CoreExpr -> CoreExpr -> CoreExpr -- Check the invariant that the arg of an App is ok-for-speculation if unlifted -- See CoreSyn Note [CoreSyn let/app invariant] mkCoreApp fun (Type ty) = App fun (Type ty) mkCoreApp fun arg = mk_val_app fun arg arg_ty res_ty where (arg_ty, res_ty) = splitFunTy (exprType fun) -- | Construct an expression which represents the application of a number of -- expressions to another. The leftmost expression in the list is applied first mkCoreApps :: CoreExpr -> [CoreExpr] -> CoreExpr -- Slightly more efficient version of (foldl mkCoreApp) mkCoreApps fun args = go fun (exprType fun) args where go fun _ [] = fun go fun fun_ty (Type ty : args) = go (App fun (Type ty)) (applyTy fun_ty ty) args go fun fun_ty (arg : args) = go (mk_val_app fun arg arg_ty res_ty) res_ty args where (arg_ty, res_ty) = splitFunTy fun_ty -- | Construct an expression which represents the application of a number of -- expressions to that of a data constructor expression. The leftmost expression -- in the list is applied first mkCoreConApps :: DataCon -> [CoreExpr] -> CoreExpr mkCoreConApps con args = mkCoreApps (Var (dataConWorkId con)) args ----------- mk_val_app :: CoreExpr -> CoreExpr -> Type -> Type -> CoreExpr mk_val_app (Var f App Type ty1 App Type _ App arg1) arg2 _ res_ty | f == seqId -- Note [Desugaring seq (1), (2)] = Case arg1 case_bndr res_ty [(DEFAULT,[],arg2)] where case_bndr = case arg1 of Var v1 | isLocalId v1 -> v1 -- Note [Desugaring seq (2) and (3)]  simonpj@microsoft.com committed Sep 15, 2008 129  _ -> mkWildId ty1  batterseapower committed Jul 31, 2008 130 131 132 133 134 135 136 137  mk_val_app fun arg arg_ty _ -- See Note [CoreSyn let/app invariant] | not (needsCaseBinding arg_ty arg) = App fun arg -- The vastly common case mk_val_app fun arg arg_ty res_ty = Case arg (mkWildId arg_ty) res_ty [(DEFAULT,[],App fun (Var arg_id))] where  simonpj@microsoft.com committed Sep 15, 2008 138  arg_id = mkWildId arg_ty -- Lots of shadowing, but it doesn't matter,  batterseapower committed Jul 31, 2008 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219  -- because 'fun ' should not have a free wild-id \end{code} Note [Desugaring seq (1)] cf Trac #1031 ~~~~~~~~~~~~~~~~~~~~~~~~~ f x y = x seq (y seq (# x,y #)) The [CoreSyn let/app invariant] means that, other things being equal, because the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus: f x y = case (y seq (# x,y #)) of v -> x seq v But that is bad for two reasons: (a) we now evaluate y before x, and (b) we can't bind v to an unboxed pair Seq is very, very special! So we recognise it right here, and desugar to case x of _ -> case y of _ -> (# x,y #) Note [Desugaring seq (2)] cf Trac #2231 ~~~~~~~~~~~~~~~~~~~~~~~~~ Consider let chp = case b of { True -> fst x; False -> 0 } in chp seq ...chp... Here the seq is designed to plug the space leak of retaining (snd x) for too long. If we rely on the ordinary inlining of seq, we'll get let chp = case b of { True -> fst x; False -> 0 } case chp of _ { I# -> ...chp... } But since chp is cheap, and the case is an alluring contet, we'll inline chp into the case scrutinee. Now there is only one use of chp, so we'll inline a second copy. Alas, we've now ruined the purpose of the seq, by re-introducing the space leak: case (case b of {True -> fst x; False -> 0}) of I# _ -> ...case b of {True -> fst x; False -> 0}... We can try to avoid doing this by ensuring that the binder-swap in the case happens, so we get his at an early stage: case chp of chp2 { I# -> ...chp2... } But this is fragile. The real culprit is the source program. Perhaps we should have said explicitly let !chp2 = chp in ...chp2... But that's painful. So the code here does a little hack to make seq more robust: a saturated application of 'seq' is turned *directly* into the case expression. So we desugar to: let chp = case b of { True -> fst x; False -> 0 } case chp of chp { I# -> ...chp... } Notice the shadowing of the case binder! And now all is well. The reason it's a hack is because if you define mySeq=seq, the hack won't work on mySeq. Note [Desugaring seq (3)] cf Trac #2409 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The isLocalId ensures that we don't turn True seq e into case True of True { ... } which stupidly tries to bind the datacon 'True'. \begin{code} -- The functions from this point don't really do anything cleverer than -- their counterparts in CoreSyn, but they are here for consistency -- | Create a lambda where the given expression has a number of variables -- bound over it. The leftmost binder is that bound by the outermost -- lambda in the result mkCoreLams :: [CoreBndr] -> CoreExpr -> CoreExpr mkCoreLams = mkLams \end{code} %************************************************************************ %* * \subsection{Making literals} %* * %************************************************************************ \begin{code} -- | Create a 'CoreExpr' which will evaluate to the given @Int@  batterseapower committed Aug 07, 2008 220 221 222 223 224 225 226 227 228 229 mkIntExpr :: Integer -> CoreExpr -- Result = I# i :: Int mkIntExpr i = mkConApp intDataCon [mkIntLit i] -- | Create a 'CoreExpr' which will evaluate to the given @Int@ mkIntExprInt :: Int -> CoreExpr -- Result = I# i :: Int mkIntExprInt i = mkConApp intDataCon [mkIntLitInt i] -- | Create a 'CoreExpr' which will evaluate to the a @Word@ with the given value mkWordExpr :: Integer -> CoreExpr mkWordExpr w = mkConApp wordDataCon [mkWordLit w]  batterseapower committed Jul 31, 2008 230 231  -- | Create a 'CoreExpr' which will evaluate to the given @Word@  batterseapower committed Aug 07, 2008 232 233 mkWordExprWord :: Word -> CoreExpr mkWordExprWord w = mkConApp wordDataCon [mkWordLitWord w]  batterseapower committed Jul 31, 2008 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595  -- | Create a 'CoreExpr' which will evaluate to the given @Integer@ mkIntegerExpr :: MonadThings m => Integer -> m CoreExpr -- Result :: Integer mkIntegerExpr i | inIntRange i -- Small enough, so start from an Int = do integer_id <- lookupId smallIntegerName return (mkSmallIntegerLit integer_id i) -- Special case for integral literals with a large magnitude: -- They are transformed into an expression involving only smaller -- integral literals. This improves constant folding. | otherwise = do -- Big, so start from a string plus_id <- lookupId plusIntegerName times_id <- lookupId timesIntegerName integer_id <- lookupId smallIntegerName let lit i = mkSmallIntegerLit integer_id i plus a b = Var plus_id App a App b times a b = Var times_id App a App b -- Transform i into (x1 + (x2 + (x3 + (...) * b) * b) * b) with abs xi <= b horner :: Integer -> Integer -> CoreExpr horner b i | abs q <= 1 = if r == 0 || r == i then lit i else lit r plus lit (i-r) | r == 0 = horner b q times lit b | otherwise = lit r plus (horner b q times lit b) where (q,r) = i quotRem b return (horner tARGET_MAX_INT i) where mkSmallIntegerLit :: Id -> Integer -> CoreExpr mkSmallIntegerLit small_integer i = mkApps (Var small_integer) [mkIntLit i] -- | Create a 'CoreExpr' which will evaluate to the given @Float@ mkFloatExpr :: Float -> CoreExpr mkFloatExpr f = mkConApp floatDataCon [mkFloatLitFloat f] -- | Create a 'CoreExpr' which will evaluate to the given @Double@ mkDoubleExpr :: Double -> CoreExpr mkDoubleExpr d = mkConApp doubleDataCon [mkDoubleLitDouble d] -- | Create a 'CoreExpr' which will evaluate to the given @Char@ mkCharExpr :: Char -> CoreExpr -- Result = C# c :: Int mkCharExpr c = mkConApp charDataCon [mkCharLit c] -- | Create a 'CoreExpr' which will evaluate to the given @String@ mkStringExpr :: MonadThings m => String -> m CoreExpr -- Result :: String -- | Create a 'CoreExpr' which will evaluate to a string morally equivalent to the given @FastString@ mkStringExprFS :: MonadThings m => FastString -> m CoreExpr -- Result :: String mkStringExpr str = mkStringExprFS (mkFastString str) mkStringExprFS str | nullFS str = return (mkNilExpr charTy) | lengthFS str == 1 = do let the_char = mkCharExpr (headFS str) return (mkConsExpr charTy the_char (mkNilExpr charTy)) | all safeChar chars = do unpack_id <- lookupId unpackCStringName return (App (Var unpack_id) (Lit (MachStr str))) | otherwise = do unpack_id <- lookupId unpackCStringUtf8Name return (App (Var unpack_id) (Lit (MachStr str))) where chars = unpackFS str safeChar c = ord c >= 1 && ord c <= 0x7F \end{code} %************************************************************************ %* * \subsection{Tuple constructors} %* * %************************************************************************ \begin{code} --$big_tuples -- #big_tuples# -- -- GHCs built in tuples can only go up to 'mAX_TUPLE_SIZE' in arity, but -- we might concievably want to build such a massive tuple as part of the -- output of a desugaring stage (notably that for list comprehensions). -- -- We call tuples above this size \"big tuples\", and emulate them by -- creating and pattern matching on >nested< tuples that are expressible -- by GHC. -- -- Nesting policy: it's better to have a 2-tuple of 10-tuples (3 objects) -- than a 10-tuple of 2-tuples (11 objects), so we want the leaves of any -- construction to be big. -- -- If you just use the 'mkBigCoreTup', 'mkBigCoreVarTupTy', 'mkTupleSelector' -- and 'mkTupleCase' functions to do all your work with tuples you should be -- fine, and not have to worry about the arity limitation at all. -- | Lifts a \"small\" constructor into a \"big\" constructor by recursive decompositon mkChunkified :: ([a] -> a) -- ^ \"Small\" constructor function, of maximum input arity 'mAX_TUPLE_SIZE' -> [a] -- ^ Possible \"big\" list of things to construct from -> a -- ^ Constructed thing made possible by recursive decomposition mkChunkified small_tuple as = mk_big_tuple (chunkify as) where -- Each sub-list is short enough to fit in a tuple mk_big_tuple [as] = small_tuple as mk_big_tuple as_s = mk_big_tuple (chunkify (map small_tuple as_s)) chunkify :: [a] -> [[a]] -- ^ Split a list into lists that are small enough to have a corresponding -- tuple arity. The sub-lists of the result all have length <= 'mAX_TUPLE_SIZE' -- But there may be more than 'mAX_TUPLE_SIZE' sub-lists chunkify xs | n_xs <= mAX_TUPLE_SIZE = [xs] | otherwise = split xs where n_xs = length xs split [] = [] split xs = take mAX_TUPLE_SIZE xs : split (drop mAX_TUPLE_SIZE xs) \end{code} Creating tuples and their types for Core expressions @mkBigCoreVarTup@ builds a tuple; the inverse to @mkTupleSelector@. * If it has only one element, it is the identity function. * If there are more elements than a big tuple can have, it nests the tuples. \begin{code} -- | Build a small tuple holding the specified variables mkCoreVarTup :: [Id] -> CoreExpr mkCoreVarTup ids = mkCoreTup (map Var ids) -- | Bulid the type of a small tuple that holds the specified variables mkCoreVarTupTy :: [Id] -> Type mkCoreVarTupTy ids = mkCoreTupTy (map idType ids) -- | Build a small tuple holding the specified expressions mkCoreTup :: [CoreExpr] -> CoreExpr mkCoreTup [] = Var unitDataConId mkCoreTup [c] = c mkCoreTup cs = mkConApp (tupleCon Boxed (length cs)) (map (Type . exprType) cs ++ cs) -- | Build the type of a small tuple that holds the specified type of thing mkCoreTupTy :: [Type] -> Type mkCoreTupTy [ty] = ty mkCoreTupTy tys = mkTupleTy Boxed (length tys) tys -- | Build a big tuple holding the specified variables mkBigCoreVarTup :: [Id] -> CoreExpr mkBigCoreVarTup ids = mkBigCoreTup (map Var ids) -- | Build the type of a big tuple that holds the specified variables mkBigCoreVarTupTy :: [Id] -> Type mkBigCoreVarTupTy ids = mkBigCoreTupTy (map idType ids) -- | Build a big tuple holding the specified expressions mkBigCoreTup :: [CoreExpr] -> CoreExpr mkBigCoreTup = mkChunkified mkCoreTup -- | Build the type of a big tuple that holds the specified type of thing mkBigCoreTupTy :: [Type] -> Type mkBigCoreTupTy = mkChunkified mkCoreTupTy \end{code} %************************************************************************ %* * \subsection{Tuple destructors} %* * %************************************************************************ \begin{code} -- | Builds a selector which scrutises the given -- expression and extracts the one name from the list given. -- If you want the no-shadowing rule to apply, the caller -- is responsible for making sure that none of these names -- are in scope. -- -- If there is just one 'Id' in the tuple, then the selector is -- just the identity. -- -- If necessary, we pattern match on a \"big\" tuple. mkTupleSelector :: [Id] -- ^ The 'Id's to pattern match the tuple against -> Id -- ^ The 'Id' to select -> Id -- ^ A variable of the same type as the scrutinee -> CoreExpr -- ^ Scrutinee -> CoreExpr -- ^ Selector expression -- mkTupleSelector [a,b,c,d] b v e -- = case e of v { -- (p,q) -> case p of p { -- (a,b) -> b }} -- We use 'tpl' vars for the p,q, since shadowing does not matter. -- -- In fact, it's more convenient to generate it innermost first, getting -- -- case (case e of v -- (p,q) -> p) of p -- (a,b) -> b mkTupleSelector vars the_var scrut_var scrut = mk_tup_sel (chunkify vars) the_var where mk_tup_sel [vars] the_var = mkSmallTupleSelector vars the_var scrut_var scrut mk_tup_sel vars_s the_var = mkSmallTupleSelector group the_var tpl_v $mk_tup_sel (chunkify tpl_vs) tpl_v where tpl_tys = [mkCoreTupTy (map idType gp) | gp <- vars_s] tpl_vs = mkTemplateLocals tpl_tys [(tpl_v, group)] = [(tpl,gp) | (tpl,gp) <- zipEqual "mkTupleSelector" tpl_vs vars_s, the_var elem gp ] \end{code} \begin{code} -- | Like 'mkTupleSelector' but for tuples that are guaranteed -- never to be \"big\". -- -- > mkSmallTupleSelector [x] x v e = [| e |] -- > mkSmallTupleSelector [x,y,z] x v e = [| case e of v { (x,y,z) -> x } |] mkSmallTupleSelector :: [Id] -- The tuple args -> Id -- The selected one -> Id -- A variable of the same type as the scrutinee -> CoreExpr -- Scrutinee -> CoreExpr mkSmallTupleSelector [var] should_be_the_same_var _ scrut = ASSERT(var == should_be_the_same_var) scrut mkSmallTupleSelector vars the_var scrut_var scrut = ASSERT( notNull vars ) Case scrut scrut_var (idType the_var) [(DataAlt (tupleCon Boxed (length vars)), vars, Var the_var)] \end{code} \begin{code} -- | A generalization of 'mkTupleSelector', allowing the body -- of the case to be an arbitrary expression. -- -- To avoid shadowing, we use uniques to invent new variables. -- -- If necessary we pattern match on a \"big\" tuple. mkTupleCase :: UniqSupply -- ^ For inventing names of intermediate variables -> [Id] -- ^ The tuple identifiers to pattern match on -> CoreExpr -- ^ Body of the case -> Id -- ^ A variable of the same type as the scrutinee -> CoreExpr -- ^ Scrutinee -> CoreExpr -- ToDo: eliminate cases where none of the variables are needed. -- -- mkTupleCase uniqs [a,b,c,d] body v e -- = case e of v { (p,q) -> -- case p of p { (a,b) -> -- case q of q { (c,d) -> -- body }}} mkTupleCase uniqs vars body scrut_var scrut = mk_tuple_case uniqs (chunkify vars) body where -- This is the case where don't need any nesting mk_tuple_case _ [vars] body = mkSmallTupleCase vars body scrut_var scrut -- This is the case where we must make nest tuples at least once mk_tuple_case us vars_s body = let (us', vars', body') = foldr one_tuple_case (us, [], body) vars_s in mk_tuple_case us' (chunkify vars') body' one_tuple_case chunk_vars (us, vs, body) = let (us1, us2) = splitUniqSupply us scrut_var = mkSysLocal (fsLit "ds") (uniqFromSupply us1) (mkCoreTupTy (map idType chunk_vars)) body' = mkSmallTupleCase chunk_vars body scrut_var (Var scrut_var) in (us2, scrut_var:vs, body') \end{code} \begin{code} -- | As 'mkTupleCase', but for a tuple that is small enough to be guaranteed -- not to need nesting. mkSmallTupleCase :: [Id] -- ^ The tuple args -> CoreExpr -- ^ Body of the case -> Id -- ^ A variable of the same type as the scrutinee -> CoreExpr -- ^ Scrutinee -> CoreExpr mkSmallTupleCase [var] body _scrut_var scrut = bindNonRec var scrut body mkSmallTupleCase vars body scrut_var scrut -- One branch no refinement? = Case scrut scrut_var (exprType body) [(DataAlt (tupleCon Boxed (length vars)), vars, body)] \end{code} %************************************************************************ %* * \subsection{Common list manipulation expressions} %* * %************************************************************************ Call the constructor Ids when building explicit lists, so that they interact well with rules. \begin{code} -- | Makes a list @[]@ for lists of the specified type mkNilExpr :: Type -> CoreExpr mkNilExpr ty = mkConApp nilDataCon [Type ty] -- | Makes a list @(:)@ for lists of the specified type mkConsExpr :: Type -> CoreExpr -> CoreExpr -> CoreExpr mkConsExpr ty hd tl = mkConApp consDataCon [Type ty, hd, tl] -- | Make a list containing the given expressions, where the list has the given type mkListExpr :: Type -> [CoreExpr] -> CoreExpr mkListExpr ty xs = foldr (mkConsExpr ty) (mkNilExpr ty) xs -- | Make a fully applied 'foldr' expression mkFoldrExpr :: MonadThings m => Type -- ^ Element type of the list -> Type -- ^ Fold result type -> CoreExpr -- ^ "Cons" function expression for the fold -> CoreExpr -- ^ "Nil" expression for the fold -> CoreExpr -- ^ List expression being folded acress -> m CoreExpr mkFoldrExpr elt_ty result_ty c n list = do foldr_id <- lookupId foldrName return (Var foldr_id App Type elt_ty App Type result_ty App c App n App list) -- | Make a 'build' expression applied to a locally-bound worker function mkBuildExpr :: (MonadThings m, MonadUnique m) => Type -- ^ Type of list elements to be built -> ((Id, Type) -> (Id, Type) -> m CoreExpr) -- ^ Function that, given information about the 'Id's -- of the binders for the build worker function, returns -- the body of that worker -> m CoreExpr mkBuildExpr elt_ty mk_build_inside = do [n_tyvar] <- newTyVars [alphaTyVar] let n_ty = mkTyVarTy n_tyvar c_ty = mkFunTys [elt_ty, n_ty] n_ty [c, n] <- sequence [mkSysLocalM (fsLit "c") c_ty, mkSysLocalM (fsLit "n") n_ty] build_inside <- mk_build_inside (c, c_ty) (n, n_ty) build_id <- lookupId buildName return$ Var build_id App Type elt_ty App mkLams [n_tyvar, c, n] build_inside where newTyVars tyvar_tmpls = do uniqs <- getUniquesM return (zipWith setTyVarUnique tyvar_tmpls uniqs) \end{code}