The Desugarer: turning HsSyn into Core.
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module Desugar ( deSugar, deSugarExpr ) where
-#include "HsVersions.h"
-
import DynFlags
import StaticFlags
import HscTypes
import Id
import Name
import CoreSyn
-import OccurAnal
import PprCore
import DsMonad
import DsExpr
import DsExpr () -- Forces DsExpr to be compiled; DsBinds only
-- depends on DsExpr.hi-boot.
import Module
-import UniqFM
-import PackageConfig
import RdrName
import NameSet
-import VarSet
import Rules
-import CoreLint
-import CoreFVs
+import CoreMonad ( endPass )
import ErrUtils
-import ListSetOps
import Outputable
import SrcLoc
import Maybes
import FastString
-import Util
import Coverage
-import IOEnv
+
import Data.IORef
\end{code}
%************************************************************************
\begin{code}
-deSugar :: HscEnv -> ModLocation -> 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_type_env = type_env,
tcg_imports = imports,
tcg_exports = exports,
- 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_inst_env = inst_env,
tcg_fam_inst_env = fam_inst_env,
- tcg_deprecs = deprecs,
+ tcg_warns = warns,
+ tcg_anns = anns,
tcg_binds = binds,
tcg_fords = fords,
tcg_rules = rules,
-- Desugar the program
; let export_set = availsToNameSet exports
- ; let auto_scc = mkAutoScc mod export_set
+ ; let auto_scc = mkAutoScc dflags mod export_set
; let target = hscTarget dflags
; let hpcInfo = emptyHpcInfo other_hpc_info
- ; mb_res <- case target of
- HscNothing -> return (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
- local_bndrs = mkVarSet (map fst all_prs)
- ; ds_rules <- mappM (dsRule mod local_bndrs) rules
- ; return (all_prs, catMaybes ds_rules, ds_fords, ds_hpc_info, modBreaks)
- }
+ ; (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 ;
+ 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 target export_set
- keep_alive all_prs ds_rules
+ 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)
mg_dir_imps = imp_mods imports,
mg_rdr_env = rdr_env,
mg_fix_env = fix_env,
- mg_deprecs = deprecs,
+ mg_warns = warns,
+ mg_anns = anns,
mg_types = type_env,
mg_insts = insts,
mg_fam_insts = fam_insts,
mg_modBreaks = modBreaks,
mg_vect_info = noVectInfo
}
- ; return (Just mod_guts)
+ ; return (msgs, Just mod_guts)
}}}
-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 target 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
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 (occurAnalyseExpr lhs') of {
- Nothing -> do { warnDs msg; return Nothing } ;
- Just (fn_id, args) -> do
-
-- Substitute the dict bindings eagerly,
-- and take the body apart into a (f args) form
+ ; 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 = 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 }
+ 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.
+
+That keeps the desugaring of list comprehensions simple too.
projects / ghc-hetmet.git / blobdiff