%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (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"
-module Desugar ( deSugar, pprDsWarnings
-#if __GLASGOW_HASKELL__ < 200
- , DsMatchContext
- , DsWarnFlavour -- fluff needed for closure,
- -- removed when compiling with 1.4
-#endif
- ) where
-
-IMP_Ubiq(){-uitous-}
-
-import HsSyn ( HsBinds, HsExpr, MonoBinds,
- SYN_IE(RecFlag), nonRecursive
- )
-import TcHsSyn ( SYN_IE(TypecheckedHsBinds), SYN_IE(TypecheckedHsExpr)
- )
+import CmdLineOpts ( DynFlag(..), dopt, opt_SccProfilingOn )
+import HscTypes ( ModGuts(..), ModGuts, HscEnv(..), GhciMode(..),
+ Dependencies(..), TypeEnv,
+ unQualInScope, availsToNameSet )
+import HsSyn ( RuleDecl(..), RuleBndr(..), HsExpr(..), LHsExpr,
+ HsBindGroup(..), LRuleDecl, HsBind(..) )
+import TcRnTypes ( TcGblEnv(..), ImportAvails(..) )
+import MkIface ( mkUsageInfo )
+import Id ( Id, setIdLocalExported, idName )
+import Name ( Name, isExternalName )
import CoreSyn
-import Name ( isExported )
+import PprCore ( pprIdRules, pprCoreExpr )
+import Subst ( substExpr, mkSubst, mkInScopeSet )
import DsMonad
-import DsBinds ( dsBinds )
-import DsUtils
-
-import Bag ( unionBags )
-import CmdLineOpts ( opt_DoCoreLinting, opt_SccGroup )
-import CostCentre ( IsCafCC(..), mkAutoCC )
-import CoreLift ( liftCoreBindings )
-import CoreLint ( lintCoreBindings )
-import Id ( nullIdEnv, mkIdEnv, idType,
- SYN_IE(DictVar), GenId, SYN_IE(Id) )
-import Outputable ( PprStyle(..) )
-import UniqSupply ( splitUniqSupply, UniqSupply )
+import DsExpr ( dsLExpr )
+import DsBinds ( dsHsBinds, AutoScc(..) )
+import DsForeign ( dsForeigns )
+import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
+ -- depends on DsExpr.hi-boot.
+import Module ( Module, moduleEnvElts, emptyModuleEnv )
+import Id ( Id )
+import RdrName ( GlobalRdrEnv )
+import NameSet
+import VarEnv
+import VarSet
+import Bag ( isEmptyBag, mapBag, emptyBag, bagToList )
+import CoreLint ( showPass, endPass )
+import CoreFVs ( ruleRhsFreeVars )
+import ErrUtils ( doIfSet, dumpIfSet_dyn, pprBagOfWarnings,
+ mkWarnMsg, errorsFound, WarnMsg )
+import Outputable
+import UniqSupply ( mkSplitUniqSupply )
+import SrcLoc ( Located(..), SrcSpan, unLoc )
+import DATA_IOREF ( readIORef )
+import FastString
\end{code}
-The only trick here is to get the @DsMonad@ stuff off to a good
-start.
+%************************************************************************
+%* *
+%* The main function: deSugar
+%* *
+%************************************************************************
\begin{code}
-deSugar :: UniqSupply -- name supply
- -> FAST_STRING -- module name
+deSugar :: HscEnv -> TcGblEnv -> IO (Maybe ModGuts)
+-- Can modify PCS by faulting in more declarations
- -> (TypecheckedHsBinds, -- input: recsel, class, instance, and value
- TypecheckedHsBinds, -- bindings; see "tcModule" (which produces
- TypecheckedHsBinds, -- them)
- TypecheckedHsBinds,
- TypecheckedHsBinds)
--- ToDo: handling of const_inst thingies is certainly WRONG ***************************
+deSugar hsc_env
+ tcg_env@(TcGblEnv { tcg_mod = mod,
+ tcg_type_env = type_env,
+ tcg_imports = imports,
+ tcg_exports = exports,
+ tcg_dus = dus,
+ tcg_inst_uses = dfun_uses_var,
+ tcg_rdr_env = rdr_env,
+ tcg_fix_env = fix_env,
+ tcg_deprecs = deprecs,
+ tcg_insts = insts })
+ = do { showPass dflags "Desugar"
- -> ([CoreBinding], -- output
- DsWarnings) -- Shadowing complaints
+ -- Do desugaring
+ ; let { is_boot = imp_dep_mods imports }
+ ; (results, warnings) <- initDs hsc_env mod type_env is_boot $
+ dsProgram ghci_mode tcg_env
-deSugar us mod_name (recsel_binds, clas_binds, inst_binds, val_binds, const_inst_binds)
- = let
- (us0, us0a) = splitUniqSupply us
- (us1, us1a) = splitUniqSupply us0a
- (us2, us2a) = splitUniqSupply us1a
- (us3, us3a) = splitUniqSupply us2a
- (us4, us5) = splitUniqSupply us3a
+ ; let { (ds_binds, ds_rules, ds_fords) = results
+ ; warns = mapBag mk_warn warnings
+ ; warn_doc = pprBagOfWarnings warns }
+
+ -- Display any warnings
+ ; doIfSet (not (isEmptyBag warnings))
+ (printErrs warn_doc)
+
+ -- If warnings are considered errors, leave.
+ ; if errorsFound dflags (warns, emptyBag)
+ then return Nothing
+ else do
+
+ -- 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
+ ; let used_names = allUses dus `unionNameSets` dfun_uses
+ ; usages <- mkUsageInfo hsc_env imports used_names
+ ; let
+ deps = Deps { dep_mods = moduleEnvElts (imp_dep_mods imports),
+ dep_pkgs = imp_dep_pkgs imports,
+ dep_orphs = imp_orphs imports }
+ mod_guts = ModGuts {
+ mg_module = mod,
+ mg_exports = exports,
+ mg_deps = deps,
+ mg_usages = usages,
+ mg_dir_imps = [m | (m,_) <- moduleEnvElts (imp_mods imports)],
+ 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 (Just mod_guts)
+ }}
+
+ where
+ dflags = hsc_dflags hsc_env
+ ghci_mode = hsc_mode hsc_env
+ print_unqual = unQualInScope rdr_env
+
+ -- Desugarer warnings are SDocs; here we
+ -- add the info about whether or not to print unqualified
+ mk_warn :: (SrcSpan,SDoc) -> WarnMsg
+ mk_warn (loc, sdoc) = mkWarnMsg loc print_unqual sdoc
+
+
+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
+ ; let { is_boot = emptyModuleEnv } -- Assume no hi-boot files when
+ -- doing stuff from the command line
+ ; (core_expr, ds_warns) <- initDs hsc_env this_mod type_env is_boot $
+ dsLExpr tc_expr
+
+ -- Display any warnings
+ -- Note: if -Werror is used, we don't signal an error here.
+ ; doIfSet (not (isEmptyBag ds_warns))
+ (printErrs (pprBagOfWarnings (mapBag mk_warn ds_warns)))
+
+ -- Dump output
+ ; dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr core_expr)
+ ; return core_expr
+ }
+ where
+ dflags = hsc_dflags hsc_env
+ print_unqual = unQualInScope rdr_env
- module_and_group = (mod_name, grp_name)
- grp_name = case opt_SccGroup of
- Just xx -> _PK_ xx
- Nothing -> mod_name -- default: module name
+ mk_warn :: (SrcSpan,SDoc) -> WarnMsg
+ mk_warn (loc,sdoc) = mkWarnMsg loc print_unqual sdoc
- (core_const_binds, shadows1)
- = initDs us0 nullIdEnv mod_name (dsBinds Nothing const_inst_binds)
- core_const_prs = pairsFromCoreBinds core_const_binds
- (core_clas_binds, shadows2)
- = initDs us1 nullIdEnv mod_name (dsBinds Nothing clas_binds)
- core_clas_prs = pairsFromCoreBinds core_clas_binds
+dsProgram ghci_mode (TcGblEnv { tcg_exports = exports,
+ tcg_keep = keep_alive,
+ tcg_binds = binds,
+ tcg_fords = fords,
+ tcg_rules = rules })
+ = dsHsBinds auto_scc binds [] `thenDs` \ core_prs ->
+ dsForeigns fords `thenDs` \ (ds_fords, foreign_prs) ->
+ let
+ all_prs = foreign_prs ++ core_prs
+ local_bndrs = mkVarSet (map fst all_prs)
+ in
+ mappM (dsRule local_bndrs) rules `thenDs` \ ds_rules ->
+ let
+ final_prs = addExportFlags ghci_mode exports keep_alive
+ local_bndrs 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#!
+ in
+ returnDs (ds_binds, ds_rules, ds_fords)
+ where
+ auto_scc | opt_SccProfilingOn = TopLevel
+ | otherwise = NoSccs
+
+-- 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 bndrs prs rules
+ = [(add_export bndr, rhs) | (bndr,rhs) <- prs]
+ where
+ add_export bndr | dont_discard bndr = setIdLocalExported bndr
+ | otherwise = bndr
+
+ orph_rhs_fvs = unionVarSets [ ruleRhsFreeVars rule
+ | (id, rule) <- rules,
+ not (id `elemVarSet` bndrs) ]
+ -- An orphan rule must keep alive the free vars
+ -- of its right-hand side.
+ -- Non-orphan rules are attached to the Id (bndr_with_rules above)
+ -- 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
- (core_inst_binds, shadows3)
- = initDs us2 nullIdEnv mod_name (dsBinds Nothing inst_binds)
- core_inst_prs = pairsFromCoreBinds core_inst_binds
+ -- 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)
- (core_val_binds, shadows4)
- = initDs us3 nullIdEnv mod_name (dsBinds (Just module_and_group) val_binds)
- core_val_pairs = pairsFromCoreBinds core_val_binds
+ppr_ds_rules [] = empty
+ppr_ds_rules rules
+ = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
+ pprIdRules rules
+\end{code}
- (core_recsel_binds, shadows5)
- = initDs us4 nullIdEnv mod_name (dsBinds Nothing recsel_binds)
- core_recsel_prs = pairsFromCoreBinds core_recsel_binds
- final_binds
- = if (null core_clas_prs && null core_inst_prs
- && null core_recsel_prs {-???dont know???-} && null core_const_prs) then
- -- we don't have to make the whole thing recursive
- core_clas_binds ++ core_val_binds
- else -- gotta make it recursive (sigh)
- [Rec (core_clas_prs ++ core_inst_prs
- ++ core_const_prs ++ core_val_pairs ++ core_recsel_prs)]
+%************************************************************************
+%* *
+%* Desugaring transformation rules
+%* *
+%************************************************************************
- lift_final_binds = liftCoreBindings us5 final_binds
+\begin{code}
+dsRule :: IdSet -> LRuleDecl Id -> DsM (Id, CoreRule)
+dsRule in_scope (L loc (HsRule name act vars lhs rhs))
+ = putSrcSpanDs loc $
+ ds_lhs all_vars lhs `thenDs` \ (fn, args) ->
+ dsLExpr rhs `thenDs` \ core_rhs ->
+ returnDs (fn, Rule name act tpl_vars args core_rhs)
+ where
+ tpl_vars = [var | RuleBndr (L _ var) <- vars]
+ all_vars = mkInScopeSet (extendVarSetList in_scope tpl_vars)
- really_final_binds = if opt_DoCoreLinting
- then lintCoreBindings PprDebug "Desugarer" False lift_final_binds
- else lift_final_binds
+ds_lhs all_vars lhs
+ = let
+ (dict_binds, body) =
+ case unLoc lhs of
+ (HsLet [HsBindGroup dict_binds _ _] body) -> (dict_binds, body)
+ other -> (emptyBag, lhs)
+ in
+ mappM ds_dict_bind (bagToList dict_binds) `thenDs` \ dict_binds' ->
+ dsLExpr body `thenDs` \ body' ->
- shadows = shadows1 `unionBags` shadows2 `unionBags`
- shadows3 `unionBags` shadows4 `unionBags` shadows5
+ -- Substitute the dict bindings eagerly,
+ -- and take the body apart into a (f args) form
+ let
+ subst_env = mkSubstEnv [id | (id,rhs) <- dict_binds']
+ [ContEx subst_env rhs | (id,rhs) <- dict_binds']
+ -- Note recursion here... substitution won't terminate
+ -- if there is genuine recursion... which there isn't
+
+ subst = mkSubst all_vars subst_env
+ body'' = substExpr subst body'
+ in
+
+ -- Now unpack the resulting body
+ let
+ pair = case collectArgs body'' of
+ (Var fn, args) -> (fn, args)
+ other -> pprPanic "dsRule" (ppr lhs)
in
- (really_final_binds, shadows)
+ returnDs pair
+
+ds_dict_bind (L _ (VarBind id rhs)) =
+ dsLExpr rhs `thenDs` \ rhs' ->
+ returnDs (id,rhs')
\end{code}
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