%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section[Desugar]{@deSugar@: the main function}
+
+The Desugarer: turning HsSyn into Core.
\begin{code}
module Desugar ( deSugar, deSugarExpr ) where
-#include "HsVersions.h"
-
-import DynFlags ( DynFlag(..), DynFlags(..), dopt, GhcMode(..) )
-import StaticFlags ( opt_SccProfilingOn,
- opt_AutoSccsOnAllToplevs,
- opt_AutoSccsOnExportedToplevs )
-import DriverPhases ( isHsBoot )
-import HscTypes ( ModGuts(..), HscEnv(..), availsToNameSet,
- 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 DynFlags
+import StaticFlags
+import HscTypes
+import HsSyn
+import TcRnTypes
+import MkIface
+import Id
+import Name
import CoreSyn
-import PprCore ( pprRules, pprCoreExpr )
+import PprCore
import DsMonad
-import DsExpr ( dsLExpr )
-import DsBinds ( dsTopLHsBinds, decomposeRuleLhs, AutoScc(..) )
-import DsForeign ( dsForeigns )
+import DsExpr
+import DsBinds
+import DsForeign
import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
-- depends on DsExpr.hi-boot.
import Module
-import UniqFM ( eltsUFM, delFromUFM )
-import PackageConfig ( thPackageId )
-import RdrName ( GlobalRdrEnv )
+import RdrName
import NameSet
-import VarSet
-import Rules ( roughTopNames )
-import CoreLint ( showPass, endPass )
-import CoreFVs ( ruleRhsFreeVars, exprsFreeNames )
-import ErrUtils ( doIfSet, dumpIfSet_dyn )
-import ListSetOps ( insertList )
+import Rules
+import CoreMonad ( endPass )
+import ErrUtils
import Outputable
-import SrcLoc ( Located(..) )
-import DATA_IOREF ( readIORef )
-import Maybes ( catMaybes )
+import SrcLoc
+import Maybes
import FastString
-import Util ( sortLe )
+import Coverage
+
+import Data.IORef
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-deSugar :: HscEnv -> TcGblEnv -> IO (Maybe ModGuts)
+-- | Main entry point to the desugarer.
+deSugar :: HscEnv -> ModLocation -> TcGblEnv -> IO (Messages, 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_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,
- tcg_fam_insts = fam_insts })
- = do { showPass dflags "Desugar"
+ mod_loc
+ tcg_env@(TcGblEnv { tcg_mod = mod,
+ tcg_src = hsc_src,
+ tcg_type_env = type_env,
+ tcg_imports = imports,
+ tcg_exports = exports,
+ tcg_keep = keep_var,
+ tcg_rdr_env = rdr_env,
+ tcg_fix_env = fix_env,
+ tcg_inst_env = inst_env,
+ tcg_fam_inst_env = fam_inst_env,
+ tcg_warns = warns,
+ tcg_anns = anns,
+ tcg_binds = binds,
+ tcg_fords = fords,
+ tcg_rules = rules,
+ tcg_insts = insts,
+ tcg_fam_insts = fam_insts,
+ tcg_hpc = other_hpc_info })
+
+ = do { let dflags = hsc_dflags hsc_env
+ ; showPass dflags "Desugar"
-- Desugar the program
; let export_set = availsToNameSet exports
- ; let auto_scc = mkAutoScc mod export_set
-
- ; mb_res <- case ghcMode dflags of
- JustTypecheck -> return (Just ([], [], NoStubs))
- _ -> 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)
- }
+ ; let auto_scc = mkAutoScc dflags mod export_set
+ ; let target = hscTarget dflags
+ ; let hpcInfo = emptyHpcInfo other_hpc_info
+ ; (msgs, mb_res)
+ <- case target of
+ HscNothing ->
+ return (emptyMessages,
+ Just ([], [], NoStubs, hpcInfo, emptyModBreaks))
+ _ -> do
+ (binds_cvr,ds_hpc_info, modBreaks)
+ <- if (opt_Hpc
+ || target == HscInterpreted)
+ && (not (isHsBoot hsc_src))
+ then addCoverageTicksToBinds dflags mod mod_loc (typeEnvTyCons type_env) binds
+ else return (binds, hpcInfo, emptyModBreaks)
+ initDs hsc_env mod rdr_env type_env $ do
+ core_prs <- dsTopLHsBinds auto_scc binds_cvr
+ (ds_fords, foreign_prs) <- dsForeigns fords
+ let all_prs = foreign_prs ++ core_prs
+ ds_rules <- mapM dsRule rules
+ return (all_prs, catMaybes ds_rules, ds_fords, ds_hpc_info, modBreaks)
+
; case mb_res of {
- Nothing -> return Nothing ;
- Just (all_prs, ds_rules, ds_fords) -> do
+ Nothing -> return (msgs, Nothing) ;
+ Just (all_prs, ds_rules, ds_fords,ds_hpc_info, modBreaks) -> do
{ -- Add export flags to bindings
keep_alive <- readIORef keep_var
- ; let final_prs = addExportFlags ghci_mode export_set
- keep_alive all_prs ds_rules
+ ; let final_prs = addExportFlags target export_set
+ keep_alive all_prs
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#
-- 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
+ ; endPass dflags "Desugar" Opt_D_dump_ds ds_binds ds_rules
-- 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
- pkgs | th_used = insertList thPackageId (imp_dep_pkgs imports)
- | otherwise = imp_dep_pkgs imports
-
- dep_mods = eltsUFM (delFromUFM (imp_dep_mods imports) (moduleName 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 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 = moduleNameFS (moduleName m1)
- <= moduleNameFS (moduleName m2)
- le_dep_mod :: (ModuleName, IsBootInterface) -> (ModuleName, IsBootInterface) -> Bool
- le_dep_mod (m1,_) (m2,_) = moduleNameFS m1 <= moduleNameFS 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_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_fam_insts = fam_insts,
- mg_rules = ds_rules,
- mg_binds = ds_binds,
- mg_foreign = ds_fords }
-
- ; return (Just mod_guts)
+ ; used_names <- mkUsedNames tcg_env
+ ; deps <- mkDependencies tcg_env
+
+ ; let mod_guts = ModGuts {
+ mg_module = mod,
+ mg_boot = isHsBoot hsc_src,
+ mg_exports = exports,
+ mg_deps = deps,
+ mg_used_names = used_names,
+ mg_dir_imps = imp_mods imports,
+ mg_rdr_env = rdr_env,
+ mg_fix_env = fix_env,
+ mg_warns = warns,
+ mg_anns = anns,
+ mg_types = type_env,
+ mg_insts = insts,
+ mg_fam_insts = fam_insts,
+ mg_inst_env = inst_env,
+ mg_fam_inst_env = fam_inst_env,
+ mg_rules = ds_rules,
+ mg_binds = ds_binds,
+ mg_foreign = ds_fords,
+ mg_hpc_info = ds_hpc_info,
+ mg_modBreaks = modBreaks,
+ mg_vect_info = noVectInfo
+ }
+ ; return (msgs, Just mod_guts)
}}}
- where
- dflags = hsc_dflags hsc_env
- ghci_mode = ghcMode (hsc_dflags hsc_env)
-
-mkAutoScc :: Module -> NameSet -> AutoScc
-mkAutoScc mod exports
+mkAutoScc :: DynFlags -> Module -> NameSet -> AutoScc
+mkAutoScc dflags mod exports
| not opt_SccProfilingOn -- No profiling
= NoSccs
- | opt_AutoSccsOnAllToplevs -- Add auto-scc on all top-level things
- = AddSccs mod (\id -> True)
- | opt_AutoSccsOnExportedToplevs -- Only on exported things
+ -- Add auto-scc on all top-level things
+ | dopt Opt_AutoSccsOnAllToplevs dflags
+ = AddSccs mod (\id -> not $ isDerivedOccName $ getOccName id)
+ -- See #1641. This is pretty yucky, but I can't see a better way
+ -- to identify compiler-generated Ids, and at least this should
+ -- catch them all.
+ -- Only on exported things
+ | dopt Opt_AutoSccsOnExportedToplevs dflags
= AddSccs mod (\id -> idName id `elemNameSet` exports)
| otherwise
= NoSccs
-
deSugarExpr :: HscEnv
-> Module -> GlobalRdrEnv -> TypeEnv
-> LHsExpr Id
- -> IO (Maybe CoreExpr)
+ -> IO (Messages, Maybe CoreExpr)
-- Prints its own errors; returns Nothing if error occurred
-deSugarExpr hsc_env this_mod rdr_env type_env tc_expr
- = do { let dflags = hsc_dflags hsc_env
- ; showPass dflags "Desugar"
+deSugarExpr hsc_env this_mod rdr_env type_env tc_expr = do
+ let dflags = hsc_dflags hsc_env
+ showPass dflags "Desugar"
- -- Do desugaring
- ; mb_core_expr <- initDs hsc_env this_mod rdr_env type_env $
- dsLExpr tc_expr
+ -- Do desugaring
+ (msgs, mb_core_expr) <- initDs hsc_env this_mod rdr_env type_env $
+ dsLExpr tc_expr
- ; case mb_core_expr of {
- Nothing -> return Nothing ;
- Just expr -> do {
+ case mb_core_expr of
+ Nothing -> return (msgs, Nothing)
+ Just expr -> do
- -- Dump output
- dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
+ -- Dump output
+ dumpIfSet_dyn dflags Opt_D_dump_ds "Desugared" (pprCoreExpr expr)
- ; return (Just expr) } } }
+ return (msgs, Just expr)
-- addExportFlags
-- Set the no-discard flag if either
-- 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
+addExportFlags :: HscTarget -> NameSet -> NameSet -> [(Id, t)]
+ -> [(Id, t)]
+addExportFlags target exports keep_alive prs
= [(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
-- 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
+ is_exported | target == HscInterpreted = isExternalName
| otherwise = (`elemNameSet` exports)
+ppr_ds_rules :: [CoreRule] -> SDoc
ppr_ds_rules [] = empty
ppr_ds_rules rules
- = text "" $$ text "-------------- DESUGARED RULES -----------------" $$
+ = blankLine $$ text "-------------- DESUGARED RULES -----------------" $$
pprRules rules
\end{code}
%************************************************************************
\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))
+dsRule :: LRuleDecl Id -> DsM (Maybe CoreRule)
+dsRule (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
+ do { let bndrs' = [var | RuleBndr (L _ var) <- vars]
+
+ ; lhs' <- unsetOptM Opt_EnableRewriteRules $
+ dsLExpr lhs -- Note [Desugaring RULE lhss]
+
; rhs' <- dsLExpr rhs
- ; case decomposeRuleLhs bndrs lhs' of {
- Nothing -> do { warnDs 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
-
- -- A rule is an orphan only if none of the variables
- -- mentioned on its left-hand side are locally defined
- 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 }
+ ; case decomposeRuleLhs (mkLams bndrs' lhs') of {
+ Nothing -> do { warnDs msg; return Nothing } ;
+ Just (bndrs, fn_id, args) -> do
+
+ { let local_rule = isLocalId fn_id
+ -- NB: isLocalId is False of implicit Ids. This is good becuase
+ -- we don't want to attach rules to the bindings of implicit Ids,
+ -- because they don't show up in the bindings until just before code gen
+ fn_name = idName fn_id
+ rule = mkRule local_rule name act fn_name bndrs args rhs'
; return (Just rule)
} } }
where
- msg = hang (ptext SLIT("RULE left-hand side too complicated to desugar; ignored"))
+ msg = hang (ptext (sLit "RULE left-hand side too complicated to desugar; ignored"))
2 (ppr lhs)
\end{code}
+
+Note [Desugaring RULE left hand sides]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For the LHS of a RULE we do *not* want to desugar
+ [x] to build (\cn. x `c` n)
+We want to leave explicit lists simply as chains
+of cons's. We can achieve that slightly indirectly by
+switching off EnableRewriteRules. See DsExpr.dsExplicitList.
+
+That keeps the desugaring of list comprehensions simple too.