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Diffstat (limited to 'compiler/deSugar/Desugar.lhs')
| -rw-r--r-- | compiler/deSugar/Desugar.lhs | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/compiler/deSugar/Desugar.lhs b/compiler/deSugar/Desugar.lhs new file mode 100644 index 0000000000..45dc113cc1 --- /dev/null +++ b/compiler/deSugar/Desugar.lhs @@ -0,0 +1,298 @@ +% +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +% +\section[Desugar]{@deSugar@: the main function} + +\begin{code} +module Desugar ( deSugar, deSugarExpr ) where + +#include "HsVersions.h" + +import DynFlags ( DynFlag(..), DynFlags(..), dopt, GhcMode(..) ) +import StaticFlags ( opt_SccProfilingOn ) +import DriverPhases ( isHsBoot ) +import HscTypes ( ModGuts(..), HscEnv(..), + Dependencies(..), ForeignStubs(..), TypeEnv, IsBootInterface ) +import HsSyn ( RuleDecl(..), RuleBndr(..), LHsExpr, LRuleDecl ) +import TcRnTypes ( TcGblEnv(..), ImportAvails(..) ) +import MkIface ( mkUsageInfo ) +import Id ( Id, setIdExported, idName ) +import Name ( Name, isExternalName, nameIsLocalOrFrom, nameOccName ) +import CoreSyn +import PprCore ( pprRules, pprCoreExpr ) +import DsMonad +import DsExpr ( dsLExpr ) +import DsBinds ( dsTopLHsBinds, decomposeRuleLhs, AutoScc(..) ) +import DsForeign ( dsForeigns ) +import DsExpr () -- Forces DsExpr to be compiled; DsBinds only + -- depends on DsExpr.hi-boot. +import Module ( Module, moduleEnvElts, delModuleEnv, moduleFS ) +import RdrName ( GlobalRdrEnv ) +import NameSet +import VarSet +import Bag ( Bag, isEmptyBag, emptyBag ) +import Rules ( roughTopNames ) +import CoreLint ( showPass, endPass ) +import CoreFVs ( ruleRhsFreeVars, exprsFreeNames ) +import Packages ( PackageState(thPackageId), PackageIdH(..) ) +import ErrUtils ( doIfSet, dumpIfSet_dyn, printBagOfWarnings, + errorsFound, WarnMsg ) +import ListSetOps ( insertList ) +import Outputable +import UniqSupply ( mkSplitUniqSupply ) +import SrcLoc ( Located(..) ) +import DATA_IOREF ( readIORef ) +import Maybes ( catMaybes ) +import FastString +import Util ( sortLe ) +\end{code} + +%************************************************************************ +%* * +%* The main function: deSugar +%* * +%************************************************************************ + +\begin{code} +deSugar :: HscEnv -> TcGblEnv -> IO (Bag WarnMsg, Maybe ModGuts) +-- Can modify PCS by faulting in more declarations + +deSugar hsc_env + tcg_env@(TcGblEnv { tcg_mod = mod, + tcg_src = hsc_src, + tcg_type_env = type_env, + tcg_imports = imports, + tcg_home_mods = home_mods, + tcg_exports = exports, + tcg_dus = dus, + tcg_inst_uses = dfun_uses_var, + tcg_th_used = th_var, + tcg_keep = keep_var, + tcg_rdr_env = rdr_env, + tcg_fix_env = fix_env, + tcg_deprecs = deprecs, + tcg_binds = binds, + tcg_fords = fords, + tcg_rules = rules, + tcg_insts = insts }) + = do { showPass dflags "Desugar" + + -- Desugar the program + ; ((all_prs, ds_rules, ds_fords), warns) + <- case ghcMode (hsc_dflags hsc_env) of + JustTypecheck -> return (([], [], NoStubs), emptyBag) + _ -> initDs hsc_env mod rdr_env type_env $ do + { core_prs <- dsTopLHsBinds auto_scc binds + ; (ds_fords, foreign_prs) <- dsForeigns fords + ; let all_prs = foreign_prs ++ core_prs + local_bndrs = mkVarSet (map fst all_prs) + ; ds_rules <- mappM (dsRule mod local_bndrs) rules + ; return (all_prs, catMaybes ds_rules, ds_fords) + } + + -- If warnings are considered errors, leave. + ; if errorsFound dflags (warns, emptyBag) + then return (warns, Nothing) + else do + + { -- Add export flags to bindings + keep_alive <- readIORef keep_var + ; let final_prs = addExportFlags ghci_mode exports keep_alive + all_prs ds_rules + ds_binds = [Rec final_prs] + -- Notice that we put the whole lot in a big Rec, even the foreign binds + -- When compiling PrelFloat, which defines data Float = F# Float# + -- we want F# to be in scope in the foreign marshalling code! + -- You might think it doesn't matter, but the simplifier brings all top-level + -- things into the in-scope set before simplifying; so we get no unfolding for F#! + + -- Lint result if necessary + ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds + + -- Dump output + ; doIfSet (dopt Opt_D_dump_ds dflags) + (printDump (ppr_ds_rules ds_rules)) + + ; dfun_uses <- readIORef dfun_uses_var -- What dfuns are used + ; th_used <- readIORef th_var -- Whether TH is used + ; let used_names = allUses dus `unionNameSets` dfun_uses + thPackage = thPackageId (pkgState dflags) + pkgs | ExtPackage th_id <- thPackage, th_used + = insertList th_id (imp_dep_pkgs imports) + | otherwise + = imp_dep_pkgs imports + + dep_mods = moduleEnvElts (delModuleEnv (imp_dep_mods imports) mod) + -- M.hi-boot can be in the imp_dep_mods, but we must remove + -- it before recording the modules on which this one depends! + -- (We want to retain M.hi-boot in imp_dep_mods so that + -- loadHiBootInterface can see if M's direct imports depend + -- on M.hi-boot, and hence that we should do the hi-boot consistency + -- check.) + + dir_imp_mods = imp_mods imports + + ; usages <- mkUsageInfo hsc_env home_mods dir_imp_mods dep_mods used_names + + ; let + -- Modules don't compare lexicographically usually, + -- but we want them to do so here. + le_mod :: Module -> Module -> Bool + le_mod m1 m2 = moduleFS m1 <= moduleFS m2 + le_dep_mod :: (Module, IsBootInterface) -> (Module, IsBootInterface) -> Bool + le_dep_mod (m1,_) (m2,_) = m1 `le_mod` m2 + + deps = Deps { dep_mods = sortLe le_dep_mod dep_mods, + dep_pkgs = sortLe (<=) pkgs, + dep_orphs = sortLe le_mod (imp_orphs imports) } + -- sort to get into canonical order + + mod_guts = ModGuts { + mg_module = mod, + mg_boot = isHsBoot hsc_src, + mg_exports = exports, + mg_deps = deps, + mg_home_mods = home_mods, + mg_usages = usages, + mg_dir_imps = [m | (m,_,_) <- moduleEnvElts dir_imp_mods], + mg_rdr_env = rdr_env, + mg_fix_env = fix_env, + mg_deprecs = deprecs, + mg_types = type_env, + mg_insts = insts, + mg_rules = ds_rules, + mg_binds = ds_binds, + mg_foreign = ds_fords } + + ; return (warns, Just mod_guts) + }} + + where + dflags = hsc_dflags hsc_env + ghci_mode = ghcMode (hsc_dflags hsc_env) + auto_scc | opt_SccProfilingOn = TopLevel + | otherwise = NoSccs + +deSugarExpr :: HscEnv + -> Module -> GlobalRdrEnv -> TypeEnv + -> LHsExpr Id + -> IO CoreExpr +deSugarExpr hsc_env this_mod rdr_env type_env tc_expr + = do { showPass dflags "Desugar" + ; us <- mkSplitUniqSupply 'd' + + -- Do desugaring + ; (core_expr, ds_warns) <- initDs hsc_env this_mod rdr_env type_env $ + dsLExpr tc_expr + + -- Display any warnings + -- Note: if -Werror is used, we don't signal an error here. + ; doIfSet (not (isEmptyBag ds_warns)) + (printBagOfWarnings dflags ds_warns) + + -- Dump output + ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr) + + ; return core_expr + } + where + dflags = hsc_dflags hsc_env + + +-- addExportFlags +-- Set the no-discard flag if either +-- a) the Id is exported +-- b) it's mentioned in the RHS of an orphan rule +-- c) it's in the keep-alive set +-- +-- It means that the binding won't be discarded EVEN if the binding +-- ends up being trivial (v = w) -- the simplifier would usually just +-- substitute w for v throughout, but we don't apply the substitution to +-- the rules (maybe we should?), so this substitution would make the rule +-- bogus. + +-- You might wonder why exported Ids aren't already marked as such; +-- it's just because the type checker is rather busy already and +-- I didn't want to pass in yet another mapping. + +addExportFlags ghci_mode exports keep_alive prs rules + = [(add_export bndr, rhs) | (bndr,rhs) <- prs] + where + add_export bndr + | dont_discard bndr = setIdExported bndr + | otherwise = bndr + + orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule + | rule <- rules, + not (isLocalRule rule) ] + -- A non-local rule keeps alive the free vars of its right-hand side. + -- (A "non-local" is one whose head function is not locally defined.) + -- Local rules are (later, after gentle simplification) + -- attached to the Id, and that keeps the rhs free vars alive. + + dont_discard bndr = is_exported name + || name `elemNameSet` keep_alive + || bndr `elemVarSet` orph_rhs_fvs + where + name = idName bndr + + -- In interactive mode, we don't want to discard any top-level + -- entities at all (eg. do not inline them away during + -- simplification), and retain them all in the TypeEnv so they are + -- available from the command line. + -- + -- isExternalName separates the user-defined top-level names from those + -- introduced by the type checker. + is_exported :: Name -> Bool + is_exported | ghci_mode == Interactive = isExternalName + | otherwise = (`elemNameSet` exports) + +ppr_ds_rules [] = empty +ppr_ds_rules rules + = text "" $$ text "-------------- DESUGARED RULES -----------------" $$ + pprRules rules +\end{code} + + + +%************************************************************************ +%* * +%* Desugaring transformation rules +%* * +%************************************************************************ + +\begin{code} +dsRule :: Module -> IdSet -> LRuleDecl Id -> DsM (Maybe CoreRule) +dsRule mod in_scope (L loc (HsRule name act vars lhs tv_lhs rhs fv_rhs)) + = putSrcSpanDs loc $ + do { let bndrs = [var | RuleBndr (L _ var) <- vars] + ; lhs' <- dsLExpr lhs + ; rhs' <- dsLExpr rhs + + ; case decomposeRuleLhs bndrs lhs' of { + Nothing -> do { dsWarn msg; return Nothing } ; + Just (bndrs', fn_id, args) -> do + + -- Substitute the dict bindings eagerly, + -- and take the body apart into a (f args) form + { let local_rule = nameIsLocalOrFrom mod fn_name + -- NB we can't use isLocalId in the orphan test, + -- because isLocalId isn't true of class methods + fn_name = idName fn_id + lhs_names = fn_name : nameSetToList (exprsFreeNames args) + -- No need to delete bndrs, because + -- exprsFreeNames finds only External names + orph = case filter (nameIsLocalOrFrom mod) lhs_names of + (n:ns) -> Just (nameOccName n) + [] -> Nothing + + rule = Rule { ru_name = name, ru_fn = fn_name, ru_act = act, + ru_bndrs = bndrs', ru_args = args, ru_rhs = rhs', + ru_rough = roughTopNames args, + ru_local = local_rule, ru_orph = orph } + ; return (Just rule) + } } } + where + msg = hang (ptext SLIT("RULE left-hand side too complicated to desugar; ignored")) + 2 (ppr lhs) +\end{code} |