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[Git][ghc/ghc][wip/T23109a] More eperiments
by Simon Peyton Jones (＠simonpj) 17 Apr '25

17 Apr '25

Simon Peyton Jones pushed to branch wip/T23109a at Glasgow Haskell Compiler / GHC Commits: bc27b6c9 by Simon Peyton Jones at 2025-04-17T13:12:48+01:00 More eperiments * Don't inline toplevel things so much * Don't float constants so vigorously in the first float-out - - - - - 3 changed files: - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Pipeline.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs Changes: ===================================== compiler/GHC/Core/Opt/OccurAnal.hs ===================================== @@ -1096,14 +1096,14 @@ mkNonRecRhsCtxt lvl bndr unf certainly_inline -- See Note [Cascading inlines] = -- mkNonRecRhsCtxt is only used for non-join points, so occAnalBind -- has set the OccInfo for this binder before calling occAnalNonRecRhs + -- Distressing delicacy ... has to line up with preInlineUnconditionally case idOccInfo bndr of OneOcc { occ_in_lam = NotInsideLam, occ_n_br = 1 } - -> active && not stable_unf && not top_bottoming + -> active && not (isTopLevel lvl) && not stable_unf _ -> False active = isAlwaysActive (idInlineActivation bndr) stable_unf = isStableUnfolding unf - top_bottoming = isTopLevel lvl && isDeadEndId bndr ----------------- occAnalRecBind :: OccEnv -> TopLevelFlag -> ImpRuleEdges -> [(Var,CoreExpr)] ===================================== compiler/GHC/Core/Opt/Pipeline.hs ===================================== @@ -217,7 +217,7 @@ getCoreToDo dflags hpt_rule_base extra_vars if full_laziness then CoreDoFloatOutwards $ FloatOutSwitches { floatOutLambdas = Just 0 - , floatOutConstants = True + , floatOutConstants = False -- Initially , floatOutOverSatApps = False , floatToTopLevelOnly = False , floatJoinsToTop = False -- Initially, don't float join points at all @@ -284,7 +284,7 @@ getCoreToDo dflags hpt_rule_base extra_vars -- f_el22 (f_el21 r_midblock) runWhen full_laziness $ CoreDoFloatOutwards $ FloatOutSwitches { floatOutLambdas = floatLamArgs dflags - , floatOutConstants = True + , floatOutConstants = True -- For SpecConstr and CSE , floatOutOverSatApps = True , floatToTopLevelOnly = False , floatJoinsToTop = True }, ===================================== compiler/GHC/Core/Opt/Simplify/Utils.hs ===================================== @@ -1461,12 +1461,18 @@ preInlineUnconditionally env top_lvl bndr rhs rhs_env extend_subst_with inl_rhs = extendIdSubst env bndr $! (mkContEx rhs_env inl_rhs) one_occ IAmDead = True -- Happens in ((\x.1) v) - one_occ OneOcc{ occ_n_br = 1 - , occ_in_lam = NotInsideLam } = isNotTopLevel top_lvl || early_phase + one_occ OneOcc{ occ_n_br = 1 + , occ_in_lam = NotInsideLam + , occ_int_cxt = int_cxt } + = isNotTopLevel top_lvl -- Get rid of allocation + || (int_cxt==IsInteresting) -- Function is applied + || (early_phase && not (isConLikeUnfolding unf)) -- See early_phase one_occ OneOcc{ occ_n_br = 1 , occ_in_lam = IsInsideLam - , occ_int_cxt = IsInteresting } = canInlineInLam rhs - one_occ _ = False + , occ_int_cxt = IsInteresting } + = canInlineInLam rhs + one_occ _ + = False pre_inline_unconditionally = sePreInline env active = isActive (sePhase env) (inlinePragmaActivation inline_prag) @@ -1641,9 +1647,10 @@ postInlineUnconditionally env bind_cxt old_bndr bndr rhs | otherwise = smallEnoughToInline uf_opts unfolding -- See Note [Post-inline for single-use things] - check_one_occ NotInsideLam _ n_br = code_dup_ok n_br - check_one_occ IsInsideLam NotInteresting _ = False - check_one_occ IsInsideLam IsInteresting n_br = is_cheap && code_dup_ok n_br + check_one_occ NotInsideLam NotInteresting n_br = not is_top_lvl && code_dup_ok n_br + check_one_occ NotInsideLam IsInteresting n_br = code_dup_ok n_br + check_one_occ IsInsideLam NotInteresting _ = False + check_one_occ IsInsideLam IsInteresting n_br = is_cheap && code_dup_ok n_br -- IsInteresting: inlining inside a lambda only with good reason -- See the notes on int_cxt in preInlineUnconditionally -- is_cheap: check for acceptable work duplication, using isCheapUnfolding View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bc27b6c9b536a8200cd2b8750e4744f… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bc27b6c9b536a8200cd2b8750e4744f… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/fendor/ghci-debugger-unitid
by Hannes Siebenhandl (＠fendor) 17 Apr '25

17 Apr '25

Hannes Siebenhandl pushed new branch wip/fendor/ghci-debugger-unitid at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/fendor/ghci-debugger-unitid You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/fendor/ghci-multiple-home-units-with-debugger] Make GHCi debugger compatible with multiple home units
by Hannes Siebenhandl (＠fendor) 17 Apr '25

17 Apr '25

Hannes Siebenhandl pushed to branch wip/fendor/ghci-multiple-home-units-with-debugger at Glasgow Haskell Compiler / GHC Commits: f071532b by fendor at 2025-04-17T13:33:14+02:00 Make GHCi debugger compatible with multiple home units FIXME: proper commit message - - - - - 11 changed files: - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/HsToCore/Breakpoints.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Runtime/Interpreter.hs - compiler/GHC/StgToByteCode.hs - libraries/ghci/GHCi/Message.hs - libraries/ghci/GHCi/Run.hs - rts/Exception.cmm - rts/Interpreter.c Changes: ===================================== compiler/GHC/ByteCode/Asm.hs ===================================== @@ -732,13 +732,16 @@ assembleI platform i = case i of CCALL off m_addr i -> do np <- addr m_addr emit_ bci_CCALL [wOp off, Op np, SmallOp i] PRIMCALL -> emit_ bci_PRIMCALL [] - BRK_FUN arr tick_mod tickx info_mod infox cc -> + BRK_FUN arr tick_mod tick_mod_id tickx info_mod info_mod_id infox cc -> do p1 <- ptr (BCOPtrBreakArray arr) tick_addr <- addr tick_mod + tick_unitid_addr <- addr tick_mod_id info_addr <- addr info_mod + info_unitid_addr <- addr info_mod_id np <- addr cc emit_ bci_BRK_FUN [ Op p1 , Op tick_addr, Op info_addr + , Op tick_unitid_addr, Op info_unitid_addr , SmallOp tickx, SmallOp infox , Op np ] ===================================== compiler/GHC/ByteCode/Instr.hs ===================================== @@ -37,6 +37,7 @@ import GHC.Stg.Syntax import GHCi.BreakArray (BreakArray) import Language.Haskell.Syntax.Module.Name (ModuleName) import GHC.Types.Unique +import GHC.Unit.Types (UnitId) -- ---------------------------------------------------------------------------- -- Bytecode instructions @@ -233,8 +234,10 @@ data BCInstr -- Breakpoints | BRK_FUN (ForeignRef BreakArray) (RemotePtr ModuleName) -- breakpoint tick module + (RemotePtr UnitId) -- breakpoint tick module unit id !Word16 -- breakpoint tick index (RemotePtr ModuleName) -- breakpoint info module + (RemotePtr UnitId) -- breakpoint info module unit id !Word16 -- breakpoint info index (RemotePtr CostCentre) @@ -403,10 +406,10 @@ instance Outputable BCInstr where ppr ENTER = text "ENTER" ppr (RETURN pk) = text "RETURN " <+> ppr pk ppr (RETURN_TUPLE) = text "RETURN_TUPLE" - ppr (BRK_FUN _ _tick_mod tickx _info_mod infox _) + ppr (BRK_FUN _ _tick_mod _tick_mod_id tickx _info_mod _info_mod_id infox _) = text "BRK_FUN" <+> text "<breakarray>" - <+> text "<tick_module>" <+> ppr tickx - <+> text "<info_module>" <+> ppr infox + <+> text "<tick_module>" <+> text "<tick_module_unitid>" <+> ppr tickx + <+> text "<info_module>" <+> text "<info_module_unitid>" <+> ppr infox <+> text "<cc>" #if MIN_VERSION_rts(1,0,3) ppr (BCO_NAME nm) = text "BCO_NAME" <+> text (show nm) ===================================== compiler/GHC/ByteCode/Types.hs ===================================== @@ -50,6 +50,7 @@ import GHC.Stack.CCS import GHC.Cmm.Expr ( GlobalRegSet, emptyRegSet, regSetToList ) import GHC.Iface.Syntax import Language.Haskell.Syntax.Module.Name (ModuleName) +import GHC.Unit.Types (UnitId) -- ----------------------------------------------------------------------------- -- Compiled Byte Code @@ -263,6 +264,9 @@ data ModBreaks , modBreaks_breakInfo :: IntMap CgBreakInfo -- ^ info about each breakpoint from the bytecode generator , modBreaks_module :: RemotePtr ModuleName + -- ^ info about the module in which we are setting the breakpoint + , modBreaks_module_unitid :: RemotePtr UnitId + -- ^ The 'UnitId' of the 'ModuleName' } seqModBreaks :: ModBreaks -> () @@ -273,7 +277,8 @@ seqModBreaks ModBreaks{..} = rnf modBreaks_decls `seq` rnf modBreaks_ccs `seq` rnf (fmap seqCgBreakInfo modBreaks_breakInfo) `seq` - rnf modBreaks_module + rnf modBreaks_module `seq` + rnf modBreaks_module_unitid -- | Construct an empty ModBreaks emptyModBreaks :: ModBreaks @@ -286,6 +291,7 @@ emptyModBreaks = ModBreaks , modBreaks_ccs = array (0,-1) [] , modBreaks_breakInfo = IntMap.empty , modBreaks_module = toRemotePtr nullPtr + , modBreaks_module_unitid = toRemotePtr nullPtr } {- ===================================== compiler/GHC/HsToCore/Breakpoints.hs ===================================== @@ -34,7 +34,7 @@ mkModBreaks interp mod extendedMixEntries breakArray <- GHCi.newBreakArray interp count ccs <- mkCCSArray interp mod count entries - mod_ptr <- GHCi.newModuleName interp (moduleName mod) + (mod_ptr, mod_id_ptr) <- GHCi.newModule interp mod let locsTicks = listArray (0,count-1) [ tick_loc t | t <- entries ] varsTicks = listArray (0,count-1) [ tick_ids t | t <- entries ] @@ -46,6 +46,7 @@ mkModBreaks interp mod extendedMixEntries , modBreaks_decls = declsTicks , modBreaks_ccs = ccs , modBreaks_module = mod_ptr + , modBreaks_module_unitid = mod_id_ptr } mkCCSArray ===================================== compiler/GHC/Runtime/Eval.hs ===================================== @@ -345,7 +345,7 @@ handleRunStatus step expr bindings final_ids status history0 = do -- Just case: we stopped at a breakpoint EvalBreak apStack_ref (Just eval_break) resume_ctxt ccs -> do - ibi <- liftIO $ evalBreakpointToId (hsc_HPT hsc_env) eval_break + let ibi = evalBreakpointToId eval_break tick_brks <- liftIO $ readModBreaks hsc_env (ibi_tick_mod ibi) let span = modBreaks_locs tick_brks ! ibi_tick_index ibi ===================================== compiler/GHC/Runtime/Interpreter.hs ===================================== @@ -21,7 +21,7 @@ module GHC.Runtime.Interpreter , mkCostCentres , costCentreStackInfo , newBreakArray - , newModuleName + , newModule , storeBreakpoint , breakpointStatus , getBreakpointVar @@ -93,9 +93,7 @@ import GHC.Utils.Outputable(brackets, ppr, showSDocUnsafe) import GHC.Utils.Fingerprint import GHC.Unit.Module -import GHC.Unit.Module.ModIface import GHC.Unit.Home.ModInfo -import GHC.Unit.Home.PackageTable import GHC.Unit.Env #if defined(HAVE_INTERNAL_INTERPRETER) @@ -119,6 +117,7 @@ import qualified GHC.InfoProv as InfoProv import GHC.Builtin.Names import GHC.Types.Name +import qualified GHC.Unit.Home.Graph as HUG -- Standard libraries import GHC.Exts @@ -377,9 +376,13 @@ newBreakArray interp size = do breakArray <- interpCmd interp (NewBreakArray size) mkFinalizedHValue interp breakArray -newModuleName :: Interp -> ModuleName -> IO (RemotePtr ModuleName) -newModuleName interp mod_name = - castRemotePtr <$> interpCmd interp (NewBreakModule (moduleNameString mod_name)) +newModule :: Interp -> Module -> IO (RemotePtr ModuleName, RemotePtr UnitId) +newModule interp mod = do + let + mod_name = moduleNameString $ moduleName mod + mod_id = unitIdString $ toUnitId $ moduleUnit mod + (mod_ptr, mod_id_ptr) <- interpCmd interp (NewBreakModule mod_name mod_id) + pure (castRemotePtr mod_ptr, castRemotePtr mod_id_ptr) storeBreakpoint :: Interp -> ForeignRef BreakArray -> Int -> Int -> IO () storeBreakpoint interp ref ix cnt = do -- #19157 @@ -415,19 +418,21 @@ seqHValue interp unit_env ref = status <- interpCmd interp (Seq hval) handleSeqHValueStatus interp unit_env status -evalBreakpointToId :: HomePackageTable -> EvalBreakpoint -> IO InternalBreakpointId -evalBreakpointToId hpt eval_break = - let load_mod x = mi_module . hm_iface . expectJust <$> lookupHpt hpt (mkModuleName x) - in do - tickl <- load_mod (eb_tick_mod eval_break) - infol <- load_mod (eb_info_mod eval_break) - return - InternalBreakpointId - { ibi_tick_mod = tickl - , ibi_tick_index = eb_tick_index eval_break - , ibi_info_mod = infol - , ibi_info_index = eb_info_index eval_break - } +evalBreakpointToId :: EvalBreakpoint -> InternalBreakpointId +evalBreakpointToId eval_break = + let + mkUnitId u = RealUnit (Definite $ stringToUnitId u) + + toModule u n = mkModule (mkUnitId u) (mkModuleName n) + tickl = toModule (eb_tick_mod_unit eval_break) (eb_tick_mod eval_break) + infol = toModule (eb_info_mod_unit eval_break) (eb_info_mod eval_break) + in + InternalBreakpointId + { ibi_tick_mod = tickl + , ibi_tick_index = eb_tick_index eval_break + , ibi_info_mod = infol + , ibi_info_index = eb_info_index eval_break + } -- | Process the result of a Seq or ResumeSeq message. #2950 handleSeqHValueStatus :: Interp -> UnitEnv -> EvalStatus () -> IO (EvalResult ()) @@ -447,12 +452,12 @@ handleSeqHValueStatus interp unit_env eval_status = mkGeneralSrcSpan (fsLit "<unknown>") Just break -> do - bi <- evalBreakpointToId (ue_hpt unit_env) break + let bi = evalBreakpointToId break -- Just case: Stopped at a breakpoint, extract SrcSpan information -- from the breakpoint. breaks_tick <- getModBreaks . expectJust <$> - lookupHpt (ue_hpt unit_env) (moduleName (ibi_tick_mod bi)) + HUG.lookupHugByModule (ibi_tick_mod bi) (ue_home_unit_graph unit_env) put $ brackets . ppr $ (modBreaks_locs breaks_tick) ! ibi_tick_index bi ===================================== compiler/GHC/StgToByteCode.hs ===================================== @@ -416,7 +416,7 @@ schemeER_wrk d p (StgTick (Breakpoint tick_ty tick_no fvs tick_mod) rhs) = do Nothing -> pure code Just current_mod_breaks -> break_info hsc_env tick_mod current_mod mb_current_mod_breaks >>= \case Nothing -> pure code - Just ModBreaks {modBreaks_flags = breaks, modBreaks_module = tick_mod_ptr, modBreaks_ccs = cc_arr} -> do + Just ModBreaks {modBreaks_flags = breaks, modBreaks_module = tick_mod_ptr, modBreaks_module_unitid = tick_mod_id_ptr, modBreaks_ccs = cc_arr} -> do platform <- profilePlatform <$> getProfile let idOffSets = getVarOffSets platform d p fvs ty_vars = tyCoVarsOfTypesWellScoped (tick_ty:map idType fvs) @@ -425,6 +425,7 @@ schemeER_wrk d p (StgTick (Breakpoint tick_ty tick_no fvs tick_mod) rhs) = do breakInfo = dehydrateCgBreakInfo ty_vars (map toWord idOffSets) tick_ty let info_mod_ptr = modBreaks_module current_mod_breaks + info_mod_id_ptr = modBreaks_module_unitid current_mod_breaks infox <- newBreakInfo breakInfo let cc | Just interp <- hsc_interp hsc_env @@ -437,7 +438,7 @@ schemeER_wrk d p (StgTick (Breakpoint tick_ty tick_no fvs tick_mod) rhs) = do in if fromIntegral r == x then r else pprPanic "schemeER_wrk: breakpoint tick/info index too large!" (ppr x) - breakInstr = BRK_FUN breaks tick_mod_ptr (toW16 tick_no) info_mod_ptr (toW16 infox) cc + breakInstr = BRK_FUN breaks tick_mod_ptr tick_mod_id_ptr (toW16 tick_no) info_mod_ptr info_mod_id_ptr (toW16 infox) cc return $ breakInstr `consOL` code schemeER_wrk d p rhs = schemeE d 0 p rhs ===================================== libraries/ghci/GHCi/Message.hs ===================================== @@ -23,6 +23,7 @@ module GHCi.Message , getMessage, putMessage, getTHMessage, putTHMessage , Pipe, mkPipeFromHandles, mkPipeFromContinuations, remoteCall, remoteTHCall, readPipe, writePipe , BreakModule + , BreakUnitId , LoadedDLL ) where @@ -245,8 +246,9 @@ data Message a where -- | Allocate a string for a breakpoint module name. -- This uses an empty dummy type because @ModuleName@ isn't available here. NewBreakModule - :: String - -> Message (RemotePtr BreakModule) + :: String -- ^ @ModuleName@ + -> String -- ^ @UnitId@ for the given @ModuleName@ + -> Message (RemotePtr BreakModule, RemotePtr BreakUnitId) deriving instance Show (Message a) @@ -410,10 +412,12 @@ data EvalStatus_ a b instance Binary a => Binary (EvalStatus_ a b) data EvalBreakpoint = EvalBreakpoint - { eb_tick_mod :: String -- ^ Breakpoint tick module - , eb_tick_index :: Int -- ^ Breakpoint tick index - , eb_info_mod :: String -- ^ Breakpoint info module - , eb_info_index :: Int -- ^ Breakpoint info index + { eb_tick_mod :: String -- ^ Breakpoint tick module + , eb_tick_mod_unit :: String -- ^ Breakpoint tick module unit id + , eb_tick_index :: Int -- ^ Breakpoint tick index + , eb_info_mod :: String -- ^ Breakpoint info module + , eb_info_mod_unit :: String -- ^ Breakpoint tick module unit id + , eb_info_index :: Int -- ^ Breakpoint info index } deriving (Generic, Show) @@ -430,6 +434,10 @@ instance Binary a => Binary (EvalResult a) -- that type isn't available here. data BreakModule +-- | A dummy type that tags the pointer to a breakpoint's @UnitId@, because +-- that type isn't available here. +data BreakUnitId + -- | A dummy type that tags pointers returned by 'LoadDLL'. data LoadedDLL @@ -580,7 +588,7 @@ getMessage = do 36 -> Msg <$> (Seq <$> get) 37 -> Msg <$> return RtsRevertCAFs 38 -> Msg <$> (ResumeSeq <$> get) - 39 -> Msg <$> (NewBreakModule <$> get) + 39 -> Msg <$> (NewBreakModule <$> get <*> get) 40 -> Msg <$> (LookupSymbolInDLL <$> get <*> get) 41 -> Msg <$> (WhereFrom <$> get) _ -> error $ "Unknown Message code " ++ (show b) @@ -627,7 +635,7 @@ putMessage m = case m of Seq a -> putWord8 36 >> put a RtsRevertCAFs -> putWord8 37 ResumeSeq a -> putWord8 38 >> put a - NewBreakModule name -> putWord8 39 >> put name + NewBreakModule name unitid -> putWord8 39 >> put name >> put unitid LookupSymbolInDLL dll str -> putWord8 40 >> put dll >> put str WhereFrom a -> putWord8 41 >> put a ===================================== libraries/ghci/GHCi/Run.hs ===================================== @@ -95,7 +95,10 @@ run m = case m of MkCostCentres mod ccs -> mkCostCentres mod ccs CostCentreStackInfo ptr -> ccsToStrings (fromRemotePtr ptr) NewBreakArray sz -> mkRemoteRef =<< newBreakArray sz - NewBreakModule name -> newModuleName name + NewBreakModule name unitid -> do + namePtr <- newModuleName name + uidPtr <- newUnitId unitid + pure (namePtr, uidPtr) SetupBreakpoint ref ix cnt -> do arr <- localRef ref; _ <- setupBreakpoint arr ix cnt @@ -335,7 +338,7 @@ withBreakAction opts breakMVar statusMVar act -- as soon as it is hit, or in resetBreakAction below. onBreak :: BreakpointCallback - onBreak tick_mod# tickx# info_mod# infox# is_exception apStack = do + onBreak tick_mod# tick_mod_uid# tickx# info_mod# info_mod_uid# infox# is_exception apStack = do tid <- myThreadId let resume = ResumeContext { resumeBreakMVar = breakMVar @@ -349,8 +352,10 @@ withBreakAction opts breakMVar statusMVar act then pure Nothing else do tick_mod <- peekCString (Ptr tick_mod#) + tick_mod_uid <- peekCString (Ptr tick_mod_uid#) info_mod <- peekCString (Ptr info_mod#) - pure (Just (EvalBreakpoint tick_mod (I# tickx#) info_mod (I# infox#))) + info_mod_uid <- peekCString (Ptr info_mod_uid#) + pure (Just (EvalBreakpoint tick_mod tick_mod_uid (I# tickx#) info_mod info_mod_uid (I# infox#))) putMVar statusMVar $ EvalBreak apStack_r breakpoint resume_r ccs takeMVar breakMVar @@ -400,8 +405,10 @@ resetStepFlag = poke stepFlag 0 type BreakpointCallback = Addr# -- pointer to the breakpoint tick module name + -> Addr# -- pointer to the breakpoint tick module unit id -> Int# -- breakpoint tick index -> Addr# -- pointer to the breakpoint info module name + -> Addr# -- pointer to the breakpoint info module unit id -> Int# -- breakpoint info index -> Bool -- exception? -> HValue -- the AP_STACK, or exception @@ -414,8 +421,8 @@ noBreakStablePtr :: StablePtr BreakpointCallback noBreakStablePtr = unsafePerformIO $ newStablePtr noBreakAction noBreakAction :: BreakpointCallback -noBreakAction _ _ _ _ False _ = putStrLn "*** Ignoring breakpoint" -noBreakAction _ _ _ _ True _ = return () -- exception: just continue +noBreakAction _ _ _ _ _ _ False _ = putStrLn "*** Ignoring breakpoint" +noBreakAction _ _ _ _ _ _ True _ = return () -- exception: just continue -- Malloc and copy the bytes. We don't have any way to monitor the -- lifetime of this memory, so it just leaks. @@ -453,6 +460,10 @@ newModuleName :: String -> IO (RemotePtr BreakModule) newModuleName name = castRemotePtr . toRemotePtr <$> newCString name +newUnitId :: String -> IO (RemotePtr BreakUnitId) +newUnitId name = + castRemotePtr . toRemotePtr <$> newCString name + getIdValFromApStack :: HValue -> Int -> IO (Maybe HValue) getIdValFromApStack apStack (I# stackDepth) = do case getApStackVal# apStack stackDepth of ===================================== rts/Exception.cmm ===================================== @@ -535,12 +535,16 @@ retry_pop_stack: // be per-thread. CInt[rts_stop_on_exception] = 0; ("ptr" ioAction) = ccall deRefStablePtr (W_[rts_breakpoint_io_action] "ptr"); - Sp = Sp - WDS(13); - Sp(12) = exception; - Sp(11) = stg_raise_ret_info; - Sp(10) = exception; - Sp(9) = ghczminternal_GHCziInternalziTypes_True_closure; // True <=> an exception - Sp(8) = stg_ap_ppv_info; + Sp = Sp - WDS(17); + Sp(16) = exception; + Sp(15) = stg_raise_ret_info; + Sp(14) = exception; + Sp(13) = ghczminternal_GHCziInternalziTypes_True_closure; // True <=> an exception + Sp(12) = stg_ap_ppv_info; + Sp(11) = 0; + Sp(10) = stg_ap_n_info; + Sp(9) = 0; + Sp(8) = stg_ap_n_info; Sp(7) = 0; Sp(6) = stg_ap_n_info; Sp(5) = 0; ===================================== rts/Interpreter.c ===================================== @@ -1245,9 +1245,9 @@ run_BCO: /* check for a breakpoint on the beginning of a let binding */ case bci_BRK_FUN: { - int arg1_brk_array, arg2_tick_mod, arg3_info_mod, arg4_tick_index, arg5_info_index; + int arg1_brk_array, arg2_tick_mod, arg3_info_mod, arg4_tick_mod_id, arg5_info_mod_id, arg6_tick_index, arg7_info_index; #if defined(PROFILING) - int arg6_cc; + int arg8_cc; #endif StgArrBytes *breakPoints; int returning_from_break; @@ -1264,10 +1264,12 @@ run_BCO: arg1_brk_array = BCO_GET_LARGE_ARG; arg2_tick_mod = BCO_GET_LARGE_ARG; arg3_info_mod = BCO_GET_LARGE_ARG; - arg4_tick_index = BCO_NEXT; - arg5_info_index = BCO_NEXT; + arg4_tick_mod_id = BCO_GET_LARGE_ARG; + arg5_info_mod_id = BCO_GET_LARGE_ARG; + arg6_tick_index = BCO_NEXT; + arg7_info_index = BCO_NEXT; #if defined(PROFILING) - arg6_cc = BCO_GET_LARGE_ARG; + arg8_cc = BCO_GET_LARGE_ARG; #else BCO_GET_LARGE_ARG; #endif @@ -1280,7 +1282,7 @@ run_BCO: #if defined(PROFILING) cap->r.rCCCS = pushCostCentre(cap->r.rCCCS, - (CostCentre*)BCO_LIT(arg6_cc)); + (CostCentre*)BCO_LIT(arg8_cc)); #endif // if we are returning from a break then skip this section @@ -1292,11 +1294,11 @@ run_BCO: // stop the current thread if either the // "rts_stop_next_breakpoint" flag is true OR if the // ignore count for this particular breakpoint is zero - StgInt ignore_count = ((StgInt*)breakPoints->payload)[arg4_tick_index]; + StgInt ignore_count = ((StgInt*)breakPoints->payload)[arg6_tick_index]; if (rts_stop_next_breakpoint == false && ignore_count > 0) { // decrement and write back ignore count - ((StgInt*)breakPoints->payload)[arg4_tick_index] = --ignore_count; + ((StgInt*)breakPoints->payload)[arg6_tick_index] = --ignore_count; } else if (rts_stop_next_breakpoint == true || ignore_count == 0) { @@ -1330,8 +1332,10 @@ run_BCO: // continue execution of this BCO when the IO action returns. // // ioAction :: Addr# -- the breakpoint tick module + // -> Addr# -- the breakpoint tick module unit id // -> Int# -- the breakpoint tick index // -> Addr# -- the breakpoint info module + // -> Addr# -- the breakpoint info module unit id // -> Int# -- the breakpoint info index // -> Bool -- exception? // -> HValue -- the AP_STACK, or exception @@ -1340,17 +1344,21 @@ run_BCO: ioAction = (StgClosure *) deRefStablePtr ( rts_breakpoint_io_action); - Sp_subW(15); - SpW(14) = (W_)obj; - SpW(13) = (W_)&stg_apply_interp_info; - SpW(12) = (W_)new_aps; - SpW(11) = (W_)False_closure; // True <=> an exception - SpW(10) = (W_)&stg_ap_ppv_info; - SpW(9) = (W_)arg5_info_index; + Sp_subW(19); + SpW(18) = (W_)obj; + SpW(17) = (W_)&stg_apply_interp_info; + SpW(16) = (W_)new_aps; + SpW(15) = (W_)False_closure; // True <=> an exception + SpW(14) = (W_)&stg_ap_ppv_info; + SpW(13) = (W_)arg7_info_index; + SpW(12) = (W_)&stg_ap_n_info; + SpW(11) = (W_)BCO_LIT(arg5_info_mod_id); + SpW(10) = (W_)&stg_ap_n_info; + SpW(9) = (W_)BCO_LIT(arg3_info_mod); SpW(8) = (W_)&stg_ap_n_info; - SpW(7) = (W_)BCO_LIT(arg3_info_mod); + SpW(7) = (W_)arg6_tick_index; SpW(6) = (W_)&stg_ap_n_info; - SpW(5) = (W_)arg4_tick_index; + SpW(5) = (W_)BCO_LIT(arg4_tick_mod_id); SpW(4) = (W_)&stg_ap_n_info; SpW(3) = (W_)BCO_LIT(arg2_tick_mod); SpW(2) = (W_)&stg_ap_n_info; View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f071532b8f1b11ef4a09989f879d8fb… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f071532b8f1b11ef4a09989f879d8fb… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/fendor/ghci-multiple-home-units] 3 commits: ghci: Use loadInterfaceForModule rather than loadSrcInterface in mkTopLevEnv
by Hannes Siebenhandl (＠fendor) 17 Apr '25

17 Apr '25

Hannes Siebenhandl pushed to branch wip/fendor/ghci-multiple-home-units at Glasgow Haskell Compiler / GHC Commits: 259ab6b7 by Matthew Pickering at 2025-04-17T13:30:37+02:00 ghci: Use loadInterfaceForModule rather than loadSrcInterface in mkTopLevEnv loadSrcInterface takes a user given `ModuleName` and resolves it to the module which needs to be loaded (taking into account module renaming/visibility etc). loadInterfaceForModule takes a specific module and loads it. The modules in `ImpDeclSpec` have already been resolved to the actual module to get the information from during renaming. Therefore we just need to fetch the precise interface from disk (and not attempt to rename it again). Fixes #25951 - - - - - 368a358b by fendor at 2025-04-17T13:30:37+02:00 Make GHCi commands compatible with multiple home units FIXME: proper commit message - - - - - f56a7898 by fendor at 2025-04-17T13:30:37+02:00 Add testcases for GHCi multiple home units Adds the following testcases: * Evaluate code with a single home unit using 'initMulti' initialisation logic * More complicated testcase with multiple home units, testing reload logic and code evaluation. - - - - - 35 changed files: - compiler/GHC.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Runtime/Context.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Unit/Home/Graph.hs - compiler/GHC/Unit/Types.hs - ghc/GHCi/UI.hs - ghc/GHCi/UI/Info.hs - ghc/GHCi/UI/Monad.hs - ghc/Main.hs - testsuite/driver/testlib.py - + testsuite/tests/ghci/prog-mhu001/Makefile - + testsuite/tests/ghci/prog-mhu001/e/E.hs - + testsuite/tests/ghci/prog-mhu001/prog-mhu001.T - + testsuite/tests/ghci/prog-mhu001/prog-mhu001.script - + testsuite/tests/ghci/prog-mhu001/prog-mhu001.stdout - + testsuite/tests/ghci/prog-mhu001/unitE - + testsuite/tests/ghci/prog-mhu002/Makefile - + testsuite/tests/ghci/prog-mhu002/a/A.hs - + testsuite/tests/ghci/prog-mhu002/b/B.hs - + testsuite/tests/ghci/prog-mhu002/c/C.hs - + testsuite/tests/ghci/prog-mhu002/d/Main.hs - + testsuite/tests/ghci/prog-mhu002/prog-mhu002.T - + testsuite/tests/ghci/prog-mhu002/prog-mhu002.script - + testsuite/tests/ghci/prog-mhu002/prog-mhu002.stderr - + testsuite/tests/ghci/prog-mhu002/prog-mhu002.stdout - + testsuite/tests/ghci/prog-mhu002/unitA - + testsuite/tests/ghci/prog-mhu002/unitB - + testsuite/tests/ghci/prog-mhu002/unitC - + testsuite/tests/ghci/prog-mhu002/unitD - + testsuite/tests/ghci/scripts/GhciPackageRename.hs - + testsuite/tests/ghci/scripts/GhciPackageRename.script - + testsuite/tests/ghci/scripts/GhciPackageRename.stdout - testsuite/tests/ghci/scripts/all.T The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/3e0b1649b2ca60207aa57e144af655… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/3e0b1649b2ca60207aa57e144af655… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/andreask/interpreter_primops] Fix some macros.
by Andreas Klebinger (＠AndreasK) 17 Apr '25

17 Apr '25

Andreas Klebinger pushed to branch wip/andreask/interpreter_primops at Glasgow Haskell Compiler / GHC Commits: 69ac44b9 by Andreas Klebinger at 2025-04-17T13:26:53+02:00 Fix some macros. - - - - - 1 changed file: - rts/Interpreter.c Changes: ===================================== rts/Interpreter.c ===================================== @@ -199,11 +199,11 @@ See also Note [Width of parameters] for some more motivation. (RTS_LIKELY(((StgWord*) Sp_plusW(n)) < ((s)->stack + (s)->stack_size - sizeofW(StgUnderflowFrame)))) -#define WDS_TO_W64(n) (n * sizeof(StgWord64) / sizeof(StgWord)) +#define W64S_TO_WDS(n) ((n) * sizeof(StgWord64) / sizeof(StgWord)) // Always safe to use - Return the value at the address #define ReadSpW(n) (*((StgWord*) SafeSpWP(n))) -#define ReadSpW64(n) (*((StgWord64*) SafeSpWP(WDS_TO_W64(n)))) +#define ReadSpW64(n) (*((StgWord64*) SafeSpWP(W64S_TO_WDS(n)))) // Perhaps confusingly this still reads a full word, merely the offset is in bytes. #define ReadSpB(n) (*((StgWord*) SafeSpBP(n))) @@ -249,9 +249,9 @@ See ticket #25750 #define SafeSpWP(n) \ ((StgWord*) ((WITHIN_CAP_CHUNK_BOUNDS_W(n)) ? Sp_plusW(n) : slow_spw(Sp, cap->r.rCurrentTSO->stackobj, n))) #define SafeSpBP(off_w) \ - ( (StgWord*) (WITHIN_CAP_CHUNK_BOUNDS_W((1+(off_w))/sizeof(StgWord))) ? \ + ( (StgWord*) ((WITHIN_CAP_CHUNK_BOUNDS_W((1+(off_w))/sizeof(StgWord))) ? \ Sp_plusB(off_w) : \ - (StgWord*) ((ptrdiff_t)((off_w) % sizeof(StgWord)) + (StgWord8*)slow_spw(Sp, cap->r.rCurrentTSO->stackobj, (off_w)/sizeof(StgWord)))) + (StgWord*) ((ptrdiff_t)((off_w) % sizeof(StgWord)) + (StgWord8*)slow_spw(Sp, cap->r.rCurrentTSO->stackobj, (off_w)/sizeof(StgWord))))) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/69ac44b9961e33059b8932b9775c24d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/69ac44b9961e33059b8932b9775c24d… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] template-haskell: Remove `addrToByteArrayName` and `addrToByteArray`
by Marge Bot (＠marge-bot) 17 Apr '25

17 Apr '25

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 386f1854 by Teo Camarasu at 2025-04-17T04:31:55-04:00 template-haskell: Remove `addrToByteArrayName` and `addrToByteArray` These were part of the implementation of the `Lift ByteArray` instance and were errornously exported because this module lacked an explicit export list. They have no usages on Hackage. Resolves #24782 - - - - - 3 changed files: - libraries/template-haskell/Language/Haskell/TH/Syntax.hs - libraries/template-haskell/changelog.md - testsuite/tests/interface-stability/template-haskell-exports.stdout Changes: ===================================== libraries/template-haskell/Language/Haskell/TH/Syntax.hs ===================================== @@ -1,6 +1,6 @@ {-# LANGUAGE MagicHash #-} {-# LANGUAGE TemplateHaskellQuotes #-} -{-# LANGUAGE Trustworthy #-} +{-# LANGUAGE Safe #-} {-# LANGUAGE UnboxedTuples #-} module Language.Haskell.TH.Syntax ( @@ -190,16 +190,11 @@ module Language.Haskell.TH.Syntax ( nothingName, rightName, trueName, - addrToByteArrayName, - addrToByteArray, ) where -import Data.Array.Byte import GHC.Boot.TH.Lift import GHC.Boot.TH.Syntax -import GHC.Exts -import GHC.ST import System.FilePath -- This module completely re-exports 'GHC.Boot.TH.Syntax', @@ -211,17 +206,3 @@ makeRelativeToProject fp | isRelative fp = do root <- getPackageRoot return (root </> fp) makeRelativeToProject fp = return fp - --- The following two defintions are copied from 'Data.Byte.Array' --- in order to preserve the old export list of 'TH.Syntax'. --- They will soon be removed as part of #24782. - -addrToByteArrayName :: Name -addrToByteArrayName = 'addrToByteArray - -addrToByteArray :: Int -> Addr# -> ByteArray -addrToByteArray (I# len) addr = runST $ ST $ - \s -> case newByteArray# len s of - (# s', mb #) -> case copyAddrToByteArray# addr mb 0# len s' of - s'' -> case unsafeFreezeByteArray# mb s'' of - (# s''', ret #) -> (# s''', ByteArray ret #) ===================================== libraries/template-haskell/changelog.md ===================================== @@ -13,6 +13,8 @@ * Remove the `Language.Haskell.TH.Lib.Internal` module. This module has long been deprecated, and exposes compiler internals. Users should use `Language.Haskell.TH.Lib` instead, which exposes a stable version of this API. + + * Remove `addrToByteArrayName` and `addrToByteArray` from `Language.Haskell.TH.Syntax`. These were part of the implementation of the `Lift ByteArray` instance and were errornously exported because this module lacked an explicit export list. They have no usages on Hackage. ## 2.23.0.0 ===================================== testsuite/tests/interface-stability/template-haskell-exports.stdout ===================================== @@ -1369,7 +1369,7 @@ module Language.Haskell.TH.Quote where quoteFile :: QuasiQuoter -> QuasiQuoter module Language.Haskell.TH.Syntax where - -- Safety: Trustworthy + -- Safety: Safe type AnnLookup :: * data AnnLookup = AnnLookupModule Module | AnnLookupName Name type AnnTarget :: * @@ -1780,8 +1780,6 @@ module Language.Haskell.TH.Syntax where addModFinalizer :: Q () -> Q () addTempFile :: GHC.Internal.Base.String -> Q GHC.Internal.IO.FilePath addTopDecls :: [Dec] -> Q () - addrToByteArray :: GHC.Internal.Types.Int -> GHC.Internal.Prim.Addr# -> Data.Array.Byte.ByteArray - addrToByteArrayName :: Name badIO :: forall a. GHC.Internal.Base.String -> GHC.Internal.Types.IO a bindCode :: forall (m :: * -> *) a (r :: GHC.Internal.Types.RuntimeRep) (b :: TYPE r). GHC.Internal.Base.Monad m => m a -> (a -> Code m b) -> Code m b bindCode_ :: forall (m :: * -> *) a (r :: GHC.Internal.Types.RuntimeRep) (b :: TYPE r). GHC.Internal.Base.Monad m => m a -> Code m b -> Code m b View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/386f18548e3c66d04f648a9d34f167a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/386f18548e3c66d04f648a9d34f167a… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] Refactor Handling of Multiple Default Declarations
by Marge Bot (＠marge-bot) 17 Apr '25

17 Apr '25

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: e0f3ff11 by Patrick at 2025-04-17T04:31:12-04:00 Refactor Handling of Multiple Default Declarations Fixes: #25912, #25914, #25934 Previously, GHC discarded all loaded defaults (tcg_default) when local defaults were encountered during typechecking. According to the exportable-named-default proposal (sections 2.4.2 and 2.4.3), local defaults should be merged into tcg_default, retaining any defaults already present while overriding where necessary. Key Changes: * Introduce DefaultProvenance to track the origin of default declarations (local, imported, or built-in), replacing the original cd_module in ClassDefaults with cd_provenance :: DefaultProvenance. * Rename tcDefaults to tcDefaultDecls, limiting its responsibility to only converting renamed class defaults into ClassDefaults. * Add extendDefaultEnvWithLocalDefaults to merge local defaults into the environment, with proper duplication checks: - Duplicate local defaults for a class trigger an error. - Local defaults override imported or built-in defaults. * Update and add related notes: Note [Builtin class defaults], Note [DefaultProvenance]. * Add regression tests: T25912, T25914, T25934. Thanks sam and simon for the help on this patch. Co-authored-by: sheaf <sam.derbyshire(a)gmail.com> - - - - - 17 changed files: - compiler/GHC/IfaceToCore.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Default.hs - compiler/GHC/Tc/Gen/Export.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Types/DefaultEnv.hs - + testsuite/tests/default/T25912.hs - + testsuite/tests/default/T25912.stdout - + testsuite/tests/default/T25912_helper.hs - + testsuite/tests/default/T25914.hs - + testsuite/tests/default/T25934.hs - testsuite/tests/default/all.T - testsuite/tests/default/default-fail03.stderr - testsuite/tests/linters/notes.stdout - testsuite/tests/module/mod58.stderr Changes: ===================================== compiler/GHC/IfaceToCore.hs ===================================== @@ -118,7 +118,7 @@ import GHC.Types.Var.Set import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Env -import GHC.Types.DefaultEnv ( ClassDefaults(..), DefaultEnv, mkDefaultEnv ) +import GHC.Types.DefaultEnv ( ClassDefaults(..), DefaultEnv, mkDefaultEnv, DefaultProvenance(..) ) import GHC.Types.Id import GHC.Types.Id.Make import GHC.Types.Id.Info @@ -1333,7 +1333,7 @@ tcIfaceDefault this_mod IfaceDefault { ifDefaultCls = cls_name ; let warn = fmap fromIfaceWarningTxt iface_warn ; return ClassDefaults { cd_class = cls , cd_types = tys' - , cd_module = Just this_mod + , cd_provenance = DP_Imported this_mod , cd_warn = warn } } where tyThingConClass :: TyThing -> Class ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -85,7 +85,7 @@ import GHC.Tc.Types.Rank (Rank(..)) import GHC.Tc.Types.TH import GHC.Tc.Utils.TcType -import GHC.Types.DefaultEnv (ClassDefaults(ClassDefaults, cd_types, cd_module)) +import GHC.Types.DefaultEnv (ClassDefaults(ClassDefaults, cd_types, cd_provenance), DefaultProvenance (..)) import GHC.Types.Error import GHC.Types.Error.Codes import GHC.Types.Hint @@ -582,11 +582,19 @@ instance Diagnostic TcRnMessage where TcRnMultipleDefaultDeclarations cls dup_things -> mkSimpleDecorated $ hang (text "Multiple default declarations for class" <+> quotes (ppr cls)) - 2 (vcat (map pp dup_things)) + 2 (pp dup_things) where - pp :: LDefaultDecl GhcRn -> SDoc - pp (L locn DefaultDecl {}) - = text "here was another default declaration" <+> ppr (locA locn) + pp :: ClassDefaults -> SDoc + pp (ClassDefaults { cd_provenance = prov }) + = case prov of + DP_Local { defaultDeclLoc = loc, defaultDeclH98 = isH98 } + -> let + what = + if isH98 + then text "default declaration" + else text "named default declaration" + in text "conflicting" <+> what <+> text "at:" <+> ppr loc + _ -> empty -- doesn't happen, as local defaults override imported and built-in defaults TcRnBadDefaultType ty deflt_clss -> mkSimpleDecorated $ hang (text "The default type" <+> quotes (ppr ty) <+> text "is not an instance of") @@ -7139,7 +7147,7 @@ pprPatersonCondFailure (PCF_TyFam tc) InTyFamEquation _lhs rhs = -------------------------------------------------------------------------------- defaultTypesAndImport :: ClassDefaults -> SDoc -defaultTypesAndImport ClassDefaults{cd_types, cd_module = Just cdm} = +defaultTypesAndImport ClassDefaults{cd_types, cd_provenance = DP_Imported cdm} = hang (parens $ pprWithCommas ppr cd_types) 2 (text "imported from" <+> ppr cdm) defaultTypesAndImport ClassDefaults{cd_types} = parens (pprWithCommas ppr cd_types) ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -1504,7 +1504,7 @@ data TcRnMessage where Text cases: module/mod58 -} - TcRnMultipleDefaultDeclarations :: Class -> [LDefaultDecl GhcRn] -> TcRnMessage + TcRnMultipleDefaultDeclarations :: Class -> ClassDefaults -> TcRnMessage {-| TcRnWarnClashingDefaultImports is a warning that occurs when a module imports more than one default declaration for the same class, and they are not all ===================================== compiler/GHC/Tc/Gen/Default.hs ===================================== @@ -5,9 +5,10 @@ -} {-# LANGUAGE MultiWayIf #-} {-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE LambdaCase #-} -- | Typechecking @default@ declarations -module GHC.Tc.Gen.Default ( tcDefaults ) where +module GHC.Tc.Gen.Default ( tcDefaultDecls, extendDefaultEnvWithLocalDefaults ) where import GHC.Prelude import GHC.Hs @@ -16,7 +17,7 @@ import GHC.Builtin.Names import GHC.Core.Class import GHC.Core.Predicate ( Pred (..), classifyPredType ) -import GHC.Data.Maybe ( firstJusts ) +import GHC.Data.Maybe ( firstJusts, maybeToList ) import GHC.Tc.Errors.Types import GHC.Tc.Gen.HsType @@ -30,20 +31,17 @@ import GHC.Tc.Utils.TcMType ( newWanted ) import GHC.Tc.Utils.TcType import GHC.Types.Basic ( TypeOrKind(..) ) -import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults (..), defaultEnv ) +import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults (..), lookupDefaultEnv, insertDefaultEnv, DefaultProvenance (..) ) import GHC.Types.SrcLoc -import GHC.Unit.Types (Module, ghcInternalUnit, moduleUnit) +import GHC.Unit.Types (ghcInternalUnit, moduleUnit) -import GHC.Utils.Misc (fstOf3, sndOf3) import GHC.Utils.Outputable import qualified GHC.LanguageExtensions as LangExt -import Data.Function (on) -import Data.List.NonEmpty ( NonEmpty (..), groupBy ) +import Data.List.NonEmpty ( NonEmpty (..) ) import qualified Data.List.NonEmpty as NE -import Data.Maybe (fromMaybe) import Data.Traversable ( for ) {- Note [Named default declarations] @@ -86,7 +84,7 @@ The moving parts are as follows: * The `DefaultEnv` of all defaults in scope in a module is kept in the `tcg_default` field of `TcGblEnv`. -* This field is populated by `GHC.Tc.Gen.Default.tcDefaults` which typechecks +* This field is populated by `GHC.Tc.Gen.Default.tcDefaultDecls` which typechecks any local or imported `default` declarations. * Only a single default declaration can be in effect in any single module for @@ -103,7 +101,7 @@ The moving parts are as follows: in effect be `default Num (Integer, Double)` as specified by Haskell Language Report. - See Note [Default class defaults] in GHC.Tc.Utils.Env + See Note [Builtin class defaults] in GHC.Tc.Utils.Env * Beside the defaults, the `ExtendedDefaultRules` and `OverloadedStrings` extensions also affect the traditional `default` declarations that don't name @@ -120,61 +118,54 @@ The moving parts are as follows: tracked separately from `ImportAvails`, and returned separately from them by `GHC.Rename.Names.rnImports`. -* Class defaults are exported explicitly, as the example above shows. A module's - exported defaults are tracked in `tcg_default_exports`, which are then - transferred to `mg_defaults`, `md_defaults`, and `mi_defaults_`. +* Class defaults are exported explicitly. + For example, + module M( ..., default C, ... ) + exports the defaults for class C. + + A module's exported defaults are computed by exports_from_avail, + tracked in tcg_default_exports, which are then transferred to mg_defaults, + md_defaults, and mi_defaults_. + + Only defaults explicitly exported are actually exported. + (i.e. No defaults are exported in a module header like: + module M where ...) + See Note [Default exports] in GHC.Tc.Gen.Export * Since the class defaults merely help the solver infer the correct types, they leave no trace in Haskell Core. -} --- See Note [Named default declarations] -tcDefaults :: [LDefaultDecl GhcRn] - -> TcM DefaultEnv -- Defaulting types to heave - -- into Tc monad for later use - -- in Disambig. - -tcDefaults [] - = getDeclaredDefaultTys -- No default declaration, so get the - -- default types from the envt; - -- i.e. use the current ones - -- (the caller will put them back there) - -- It's important not to return defaultDefaultTys here (which - -- we used to do) because in a TH program, tcDefaults [] is called - -- repeatedly, once for each group of declarations between top-level - -- splices. We don't want to carefully set the default types in - -- one group, only for the next group to ignore them and install - -- defaultDefaultTys - -tcDefaults decls - = do { tcg_env <- getGblEnv - ; let - here = tcg_mod tcg_env - is_internal_unit = moduleUnit here == ghcInternalUnit - ; case (is_internal_unit, decls) of - -- Some internal GHC modules contain @default ()@ to declare that no defaults can take place - -- in the module. - -- We shortcut the treatment of such a default declaration with no class nor types: we won't - -- try to point 'cd_class' to 'Num' since it may not even exist yet. - { (True, [L _ (DefaultDecl _ Nothing [])]) - -> return $ defaultEnv [] - -- Otherwise we take apart the declaration into the class constructor and its default types. - ; _ -> - do { h2010_dflt_clss <- getH2010DefaultClasses - ; decls' <- mapMaybeM (declarationParts h2010_dflt_clss) decls - ; let - -- Find duplicate default declarations - decl_tag (mb_cls, _, _) = - case mb_cls of - Nothing -> Nothing - Just cls -> if cls `elem` h2010_dflt_clss - then Nothing - else Just cls - decl_groups = groupBy ((==) `on` decl_tag) decls' - ; decls_without_dups <- mapM (reportDuplicates here h2010_dflt_clss) decl_groups - ; return $ defaultEnv (concat decls_without_dups) - } } } +-- | Typecheck a collection of default declarations. These can be either: +-- +-- - Haskell 98 default declarations, of the form @default (Float, Double)@ +-- - Named default declarations, of the form @default Cls(Int, Char)@. +-- See Note [Named default declarations] +tcDefaultDecls :: [LDefaultDecl GhcRn] -> TcM [LocatedA ClassDefaults] +tcDefaultDecls decls = + do + tcg_env <- getGblEnv + let here = tcg_mod tcg_env + is_internal_unit = moduleUnit here == ghcInternalUnit + case (is_internal_unit, decls) of + -- No default declarations + (_, []) -> return [] + -- As per Remark [default () in ghc-internal] in Note [Builtin class defaults], + -- some modules in ghc-internal include an empty `default ()` declaration, in order + -- to disable built-in defaults. This is no longer necessary (see `GHC.Tc.Utils.Env.tcGetDefaultTys`), + -- but we must still make sure not to error if we fail to look up e.g. the 'Num' + -- typeclass when typechecking such a default declaration. To do this, we wrap + -- calls of 'tcLookupClass' in 'tryTc'. + (True, [L _ (DefaultDecl _ Nothing [])]) -> do + h2010_dflt_clss <- foldMapM (fmap maybeToList . fmap fst . tryTc . tcLookupClass) =<< getH2010DefaultNames + case NE.nonEmpty h2010_dflt_clss of + Nothing -> return [] + Just h2010_dflt_clss' -> toClassDefaults h2010_dflt_clss' decls + -- Otherwise we take apart the declaration into the class constructor and its default types. + _ -> do + h2010_dflt_clss <- getH2010DefaultClasses + toClassDefaults h2010_dflt_clss decls where getH2010DefaultClasses :: TcM (NonEmpty Class) -- All the classes subject to defaulting with a Haskell 2010 default @@ -186,18 +177,18 @@ tcDefaults decls -- No extensions: Num -- OverloadedStrings: add IsString -- ExtendedDefaults: add Show, Eq, Ord, Foldable, Traversable - getH2010DefaultClasses - = do { num_cls <- tcLookupClass numClassName - ; ovl_str <- xoptM LangExt.OverloadedStrings + getH2010DefaultClasses = mapM tcLookupClass =<< getH2010DefaultNames + getH2010DefaultNames + = do { ovl_str <- xoptM LangExt.OverloadedStrings ; ext_deflt <- xoptM LangExt.ExtendedDefaultRules - ; deflt_str <- if ovl_str - then mapM tcLookupClass [isStringClassName] - else return [] - ; deflt_interactive <- if ext_deflt - then mapM tcLookupClass interactiveClassNames - else return [] - ; let extra_clss = deflt_str ++ deflt_interactive - ; return $ num_cls :| extra_clss + ; let deflt_str = if ovl_str + then [isStringClassName] + else [] + ; let deflt_interactive = if ext_deflt + then interactiveClassNames + else [] + ; let extra_clss_names = deflt_str ++ deflt_interactive + ; return $ numClassName :| extra_clss_names } declarationParts :: NonEmpty Class -> LDefaultDecl GhcRn -> TcM (Maybe (Maybe Class, LDefaultDecl GhcRn, [Type])) declarationParts h2010_dflt_clss decl@(L locn (DefaultDecl _ mb_cls_name dflt_hs_tys)) @@ -220,20 +211,49 @@ tcDefaults decls ; return (Just cls, decl, tau_tys) } } - reportDuplicates :: Module -> NonEmpty Class -> NonEmpty (Maybe Class, LDefaultDecl GhcRn, [Type]) -> TcM [ClassDefaults] - reportDuplicates here h2010_dflt_clss ((mb_cls, _, tys) :| []) - = pure [ ClassDefaults{cd_class = c, cd_types = tys, cd_module = Just here, cd_warn = Nothing } - | c <- case mb_cls of - Nothing -> NE.toList h2010_dflt_clss - Just cls -> [cls] - ] - -- Report an error on multiple default declarations for the same class in the same module. - -- See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module - reportDuplicates _ (num_cls :| _) decls@((_, L locn _, _) :| _) - = setSrcSpan (locA locn) (addErrTc $ dupDefaultDeclErr cls (sndOf3 <$> decls)) - >> pure [] + toClassDefaults :: NonEmpty Class -> [LDefaultDecl GhcRn] -> TcM [LocatedA ClassDefaults] + toClassDefaults h2010_dflt_clss dfs = do + dfs <- mapMaybeM (declarationParts h2010_dflt_clss) dfs + return $ concatMap (go False) dfs where - cls = fromMaybe num_cls $ firstJusts (fmap fstOf3 decls) + go h98 = \case + (Nothing, rn_decl, tys) -> concatMap (go True) [(Just cls, rn_decl, tys) | cls <- NE.toList h2010_dflt_clss] + (Just cls, (L locn _), tys) -> [(L locn $ ClassDefaults cls tys (DP_Local (locA locn) h98) Nothing)] + +-- | Extend the default environment with the local default declarations +-- and do the action in the extended environment. +extendDefaultEnvWithLocalDefaults :: [LocatedA ClassDefaults] -> TcM a -> TcM a +extendDefaultEnvWithLocalDefaults decls action = do + tcg_env <- getGblEnv + let default_env = tcg_default tcg_env + new_default_env <- insertDefaultDecls default_env decls + updGblEnv (\gbl -> gbl { tcg_default = new_default_env } ) $ action + +-- | Insert local default declarations into the default environment. +-- +-- See 'insertDefaultDecl'. +insertDefaultDecls :: DefaultEnv -> [LocatedA ClassDefaults] -> TcM DefaultEnv +insertDefaultDecls = foldrM insertDefaultDecl +-- | Insert a local default declaration into the default environment. +-- +-- If the class already has a local default declaration in the DefaultEnv, +-- report an error and return the original DefaultEnv. Otherwise, override +-- any existing default declarations (e.g. imported default declarations). +-- +-- See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module +insertDefaultDecl :: LocatedA ClassDefaults -> DefaultEnv -> TcM DefaultEnv +insertDefaultDecl (L decl_loc new_cls_defaults ) default_env = + case lookupDefaultEnv default_env (className cls) of + Just cls_defaults + | DP_Local {} <- cd_provenance cls_defaults + -> do { setSrcSpan (locA decl_loc) (addErrTc $ TcRnMultipleDefaultDeclarations cls cls_defaults) + ; return default_env } + _ -> return $ insertDefaultEnv new_cls_defaults default_env + -- NB: this overrides imported and built-in default declarations + -- for this class, if there were any. + where + cls = cd_class new_cls_defaults + -- | Check that the type is an instance of at least one of the default classes. -- @@ -289,10 +309,6 @@ simplifyDefault cls dflt_ty@(L l _) -> Nothing } -dupDefaultDeclErr :: Class -> NonEmpty (LDefaultDecl GhcRn) -> TcRnMessage -dupDefaultDeclErr cls (L _ DefaultDecl {} :| dup_things) - = TcRnMultipleDefaultDeclarations cls dup_things - {- Note [Instance check for default declarations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When we see a named default declaration, such as: @@ -327,4 +343,4 @@ whether each type is an instance of: - ... or the IsString class, with -XOverloadedStrings - ... or any of the Show, Eq, Ord, Foldable, and Traversable classes, with -XExtendedDefaultRules --} \ No newline at end of file +-} ===================================== compiler/GHC/Tc/Gen/Export.hs ===================================== @@ -282,7 +282,7 @@ example, would import the above `default IsString (Text, String)` declaration into the importing module. -The `cd_module` field of `ClassDefaults` tracks the module whence the default was +The `cd_provenance` field of `ClassDefaults` tracks the module whence the default was imported from, for the purpose of warning reports. The said warning report may be triggered by `-Wtype-defaults` or by a user-defined `WARNING` pragma attached to the default export. In the latter case the warning text is stored in the ===================================== compiler/GHC/Tc/Module.hs ===================================== @@ -383,6 +383,7 @@ the actual contents of the module are wired in to GHC. -} {- Note [Disambiguation of multiple default declarations] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See Note [Named default declarations] in GHC.Tc.Gen.Default @@ -1811,9 +1812,8 @@ tcTyClsInstDecls tycl_decls deriv_decls default_decls binds -- -- But only after we've typechecked 'default' declarations. -- See Note [Typechecking default declarations] - defaults <- tcDefaults default_decls ; - updGblEnv (\gbl -> gbl { tcg_default = defaults }) $ do { - + defaults <- tcDefaultDecls default_decls + ; extendDefaultEnvWithLocalDefaults defaults $ do { -- Careful to quit now in case there were instance errors, so that -- the deriving errors don't pile up as well. ===================================== compiler/GHC/Tc/Utils/Env.hs ===================================== @@ -128,8 +128,7 @@ import GHC.Types.SourceFile import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Env -import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults(..), - defaultEnv, emptyDefaultEnv, lookupDefaultEnv, unitDefaultEnv ) +import GHC.Types.DefaultEnv import GHC.Types.Error import GHC.Types.Id import GHC.Types.Id.Info ( RecSelParent(..) ) @@ -971,21 +970,28 @@ isBrackStage _other = False ************************************************************************ -} -{- Note [Default class defaults] +{- Note [Builtin class defaults] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -In absence of user-defined `default` declarations, the set of class defaults in -effect (i.e. `DefaultEnv`) is determined by the absence or -presence of the `ExtendedDefaultRules` and `OverloadedStrings` extensions. In their -absence, the only rule in effect is `default Num (Integer, Double)` as specified by -Haskell Language Report. - -In GHC's internal packages `DefaultEnv` is empty to minimize cross-module dependencies: -the `Num` class or `Integer` type may not even be available in low-level modules. If -you don't do this, attempted defaulting in package ghc-prim causes an actual crash -(attempting to look up the `Integer` type). - -A user-defined `default` declaration overrides the defaults for the specified class, -and only for that class. +In the absence of user-defined `default` declarations, the set of class defaults in +effect (i.e. the `DefaultEnv`) depends on whether the `ExtendedDefaultRules` and +`OverloadedStrings` extensions are enabled. In their absence, the only rule in effect +is `default Num (Integer, Double)`, as specified by the Haskell 2010 report. + +Remark [No built-in defaults in ghc-internal] + + When typechecking the ghc-internal package, we **do not** include any built-in + defaults. This is because, in ghc-internal, types such as 'Num' or 'Integer' may + not even be available (they haven't been typechecked yet). + +Remark [default () in ghc-internal] + + Historically, modules inside ghc-internal have used a single default declaration, + of the form `default ()`, to work around the problem described in + Remark [No built-in defaults in ghc-internal]. + + When we typecheck such a default declaration, we must also make sure not to fail + if e.g. 'Num' is not in scope. We thus have special treatment for this case, + in 'GHC.Tc.Gen.Default.tcDefaultDecls'. -} tcGetDefaultTys :: TcM (DefaultEnv, -- Default classes and types @@ -997,7 +1003,7 @@ tcGetDefaultTys -- See also #1974 builtinDefaults cls tys = ClassDefaults{ cd_class = cls , cd_types = tys - , cd_module = Nothing + , cd_provenance = DP_Builtin , cd_warn = Nothing } -- see Note [Named default declarations] in GHC.Tc.Gen.Default @@ -1005,7 +1011,8 @@ tcGetDefaultTys ; this_module <- tcg_mod <$> getGblEnv ; let this_unit = moduleUnit this_module ; if this_unit == ghcInternalUnit - -- see Note [Default class defaults] + -- see Remark [No built-in defaults in ghc-internal] + -- in Note [Builtin class defaults] in GHC.Tc.Utils.Env then return (defaults, extended_defaults) else do -- not one of the built-in units @@ -1037,6 +1044,8 @@ tcGetDefaultTys } -- The Num class is already user-defaulted, no need to construct the builtin default _ -> pure emptyDefaultEnv + -- Supply the built-in defaults, but make the user-supplied defaults + -- override them. ; let deflt_tys = mconcat [ extDef, numDef, ovlStr, defaults ] ; return (deflt_tys, extended_defaults) } } ===================================== compiler/GHC/Types/DefaultEnv.hs ===================================== @@ -1,7 +1,9 @@ {-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE LambdaCase #-} module GHC.Types.DefaultEnv ( ClassDefaults (..) + , DefaultProvenance (..) , DefaultEnv , emptyDefaultEnv , isEmptyDefaultEnv @@ -12,6 +14,8 @@ module GHC.Types.DefaultEnv , defaultList , plusDefaultEnv , mkDefaultEnv + , insertDefaultEnv + , isHaskell2010Default ) where @@ -22,6 +26,7 @@ import GHC.Tc.Utils.TcType (Type) import GHC.Types.Name (Name, nameUnique, stableNameCmp) import GHC.Types.Name.Env import GHC.Types.Unique.FM (lookupUFM_Directly) +import GHC.Types.SrcLoc (SrcSpan) import GHC.Unit.Module.Warnings (WarningTxt) import GHC.Unit.Types (Module) import GHC.Utils.Outputable @@ -37,13 +42,73 @@ import Data.Function (on) -- NB: this includes Haskell98 default declarations, at the 'Num' key. type DefaultEnv = NameEnv ClassDefaults +{- Note [DefaultProvenance] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Each `ClassDefault` is annotated with its `DefaultProvenance`, which +says where the default came from. Specifically +* `DP_Local loc h98`: the default came from an explicit `default` declaration in the module + being compiled, at location `loc`, and the boolean `h98` indicates whether + it was from a Haskell 98 default declaration (e.g. `default (Int, Double)`). +* `DP_Imported M`: the default was imported, it is explicitly exported by module `M`. +* `DP_Builtin`: the default was automatically provided by GHC. + see Note [Builtin class defaults] in GHC.Tc.Utils.Env + +These annotations are used to disambiguate multiple defaults for the same class. +For example, consider the following modules: + + module M( default C ) where { default C( ... ) } + module M2( default C) where { import M } + module N( default C () where { default C(... ) } + + module A where { import M2 } + module B where { import M2; import N } + module A1 where { import N; default C ( ... ) } + module B2 where { default C ( ... ); default C ( ... ) } + +When compiling N, the default for C is annotated with DP_Local loc. +When compiling M2, the default for C is annotated with DP_Local M. +When compiling A, the default for C is annotated with DP_Imported M2. + +Cases we needed to disambiguate: + * Compiling B, two defaults for C: DP_Imported M2, DP_Imported N. + * Compiling A1, two defaults for C: DP_Imported N, DP_Local loc. + * Compiling B2, two defaults for C: DP_Local loc1, DP_Local loc2. + +For how we disambiguate these cases, +See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module. +-} + +-- | The provenance of a collection of default types for a class. +-- see Note [DefaultProvenance] for more details +data DefaultProvenance + -- | A locally defined default declaration. + = DP_Local + { defaultDeclLoc :: SrcSpan -- ^ The 'SrcSpan' of the default declaration + , defaultDeclH98 :: Bool -- ^ Is this a Haskell 98 default declaration? + } + -- | Built-in class defaults. + | DP_Builtin + -- | Imported class defaults. + | DP_Imported Module -- ^ The module from which the defaults were imported + deriving (Eq, Data) + +instance Outputable DefaultProvenance where + ppr (DP_Local loc h98) = ppr loc <> (if h98 then text " (H98)" else empty) + ppr DP_Builtin = text "built-in" + ppr (DP_Imported mod) = ppr mod + +isHaskell2010Default :: DefaultProvenance -> Bool +isHaskell2010Default = \case + DP_Local { defaultDeclH98 = isH98 } -> isH98 + DP_Builtin -> True + DP_Imported {} -> False + -- | Defaulting type assignments for the given class. data ClassDefaults = ClassDefaults { cd_class :: Class -- ^ The class whose defaults are being defined , cd_types :: [Type] - , cd_module :: Maybe Module - -- ^ @Nothing@ for built-in, - -- @Just@ the current module or the module whence the default was imported + , cd_provenance :: DefaultProvenance + -- ^ Where the defaults came from -- see Note [Default exports] in GHC.Tc.Gen.Export , cd_warn :: Maybe (WarningTxt GhcRn) -- ^ Warning emitted when the default is used @@ -70,6 +135,9 @@ defaultList :: DefaultEnv -> [ClassDefaults] defaultList = sortBy (stableNameCmp `on` className . cd_class) . nonDetNameEnvElts -- sortBy recovers determinism +insertDefaultEnv :: ClassDefaults -> DefaultEnv -> DefaultEnv +insertDefaultEnv d env = extendNameEnv env (className $ cd_class d) d + lookupDefaultEnv :: DefaultEnv -> Name -> Maybe ClassDefaults lookupDefaultEnv env = lookupUFM_Directly env . nameUnique ===================================== testsuite/tests/default/T25912.hs ===================================== @@ -0,0 +1,14 @@ +{-# LANGUAGE NamedDefaults #-} + +module Main where + +import T25912_helper + +-- now we declare the default instances +-- for the classes C again to check that +-- it won't hide the default instances for class B +default C (String) + +main :: IO () +main = do + print b ===================================== testsuite/tests/default/T25912.stdout ===================================== @@ -0,0 +1 @@ +"String" ===================================== testsuite/tests/default/T25912_helper.hs ===================================== @@ -0,0 +1,17 @@ +{-# LANGUAGE NamedDefaults #-} + +module T25912_helper ( default C, C(c), default B, b ) where + +class C a where + c :: a +instance C Int where + c = 1 +instance C String where + c = "String" +default C (String) + +class B a where + b :: a +instance B String where + b = "String" +default B (String) ===================================== testsuite/tests/default/T25914.hs ===================================== @@ -0,0 +1,5 @@ +{-# LANGUAGE NamedDefaults, OverloadedStrings #-} +module NamedDefaultsNum where +import Data.String +default Num () +foo = "abc" ===================================== testsuite/tests/default/T25934.hs ===================================== @@ -0,0 +1,5 @@ +{-# LANGUAGE ExtendedDefaultRules #-} +{-# LANGUAGE NamedDefaults #-} +module T25934 where +default Num (Int) +default Show (Int) ===================================== testsuite/tests/default/all.T ===================================== @@ -39,3 +39,6 @@ test('T25858v2', [extra_files(['T25858v2_helper.hs'])], multimod_compile_and_run test('T25858v3', [extra_files(['T25858v3_helper.hs'])], multimod_compile_and_run, ['T25858v3', '']) test('T25858v4', normal, compile_and_run, ['']) test('T25882', normal, compile, ['']) +test('T25912', [extra_files(['T25912_helper.hs'])], multimod_compile_and_run, ['T25912', '']) +test('T25914', normal, compile, ['']) +test('T25934', normal, compile, ['']) ===================================== testsuite/tests/default/default-fail03.stderr ===================================== @@ -1,3 +1,4 @@ -default-fail03.hs:4:1: [GHC-99565] +default-fail03.hs:4:1: error: [GHC-99565] Multiple default declarations for class ‘Num’ - here was another default declaration default-fail03.hs:3:1-29 + conflicting named default declaration at: default-fail03.hs:3:1-29 + ===================================== testsuite/tests/linters/notes.stdout ===================================== @@ -8,7 +8,7 @@ ref compiler/GHC/Core/Opt/Simplify/Iteration.hs:4345:8: Note [Lambda-boun ref compiler/GHC/Core/Opt/Simplify/Utils.hs:1387:37: Note [Gentle mode] ref compiler/GHC/Core/Opt/Specialise.hs:1761:29: Note [Arity decrease] ref compiler/GHC/Core/TyCo/Rep.hs:1783:31: Note [What prevents a constraint from floating] -ref compiler/GHC/Driver/DynFlags.hs:1216:52: Note [Eta-reduction in -O0] +ref compiler/GHC/Driver/DynFlags.hs:1218:52: Note [Eta-reduction in -O0] ref compiler/GHC/Driver/Main.hs:1901:34: Note [simpleTidyPgm - mkBootModDetailsTc] ref compiler/GHC/Hs/Expr.hs:189:63: Note [Pending Splices] ref compiler/GHC/Hs/Expr.hs:2194:87: Note [Lifecycle of a splice] @@ -18,10 +18,8 @@ ref compiler/GHC/Hs/Pat.hs:151:74: Note [Lifecycle of a splice] ref compiler/GHC/HsToCore/Pmc/Solver.hs:860:20: Note [COMPLETE sets on data families] ref compiler/GHC/HsToCore/Quote.hs:1533:7: Note [How brackets and nested splices are handled] ref compiler/GHC/Stg/Unarise.hs:457:32: Note [Renaming during unarisation] -ref compiler/GHC/Tc/Gen/Default.hs:87:6: Note [Disambiguation of multiple default declarations] -ref compiler/GHC/Tc/Gen/Default.hs:193:11: Note [Disambiguation of multiple default declarations] ref compiler/GHC/Tc/Gen/HsType.hs:563:56: Note [Skolem escape prevention] -ref compiler/GHC/Tc/Gen/HsType.hs:2693:7: Note [Matching a kind signature with a declaration] +ref compiler/GHC/Tc/Gen/HsType.hs:2717:7: Note [Matching a kind signature with a declaration] ref compiler/GHC/Tc/Gen/Pat.hs:284:20: Note [Typing patterns in pattern bindings] ref compiler/GHC/Tc/Gen/Pat.hs:1378:7: Note [Matching polytyped patterns] ref compiler/GHC/Tc/Gen/Sig.hs:91:10: Note [Overview of type signatures] @@ -30,8 +28,6 @@ ref compiler/GHC/Tc/Gen/Splice.hs:543:35: Note [PendingRnSplice] ref compiler/GHC/Tc/Gen/Splice.hs:670:7: Note [How brackets and nested splices are handled] ref compiler/GHC/Tc/Gen/Splice.hs:909:11: Note [How brackets and nested splices are handled] ref compiler/GHC/Tc/Instance/Family.hs:458:35: Note [Constrained family instances] -ref compiler/GHC/Tc/Module.hs:385:3: Note [Disambiguation of multiple default declarations] -ref compiler/GHC/Tc/Module.hs:420:7: Note [Disambiguation of multiple default declarations] ref compiler/GHC/Tc/Solver/Rewrite.hs:1015:7: Note [Stability of rewriting] ref compiler/GHC/Tc/TyCl.hs:1322:6: Note [Unification variables need fresh Names] ref compiler/GHC/Tc/Types/Constraint.hs:209:9: Note [NonCanonical Semantics] ===================================== testsuite/tests/module/mod58.stderr ===================================== @@ -1,4 +1,4 @@ - mod58.hs:4:1: error: [GHC-99565] Multiple default declarations for class ‘Num’ - here was another default declaration mod58.hs:3:1-21 + conflicting default declaration at: mod58.hs:3:1-21 + View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e0f3ff11719f1ee343d1b5d1fd3193d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e0f3ff11719f1ee343d1b5d1fd3193d… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T25965] Fix infelicities in the Specialiser
by Simon Peyton Jones (＠simonpj) 17 Apr '25

17 Apr '25

Simon Peyton Jones pushed to branch wip/T25965 at Glasgow Haskell Compiler / GHC Commits: 3909c689 by Simon Peyton Jones at 2025-04-17T09:06:59+01:00 Fix infelicities in the Specialiser On the way to #23109 (unary classes) I discovered some infelicities (or maybe tiny bugs, I forget) in the type-class specialiser. I also tripped over #25965, an outright bug in the rule matcher Specifically: * Refactor: I enhanced `wantCallsFor`, whih previously always said `True`, to discard calls of class-ops, data constructors etc. This is a bit more efficient; and it means we don't need to worry about filtering them out later. * Fix: I tidied up some tricky logic that eliminated redundant specialisations. It wasn't working correctly. See the expanded Note [Specialisations already covered], and (MP3) in Note [Specialising polymorphic dictionaries]. See also the new top-level `alreadyCovered` function, which now goes via `GHC.Core.Rules.ruleLhsIsMoreSpecific` I also added a useful Note [The (CI-KEY) invariant] * Fix #25965: fixed a tricky bug in the `go_fam_fam` in `GHC.Core.Unify.uVarOrFam`, which allows matching to succeed without binding all type varibles. I enhanced Note [Apartness and type families] some more * #25703. This ticket "just works" with -fpolymorphic-specialisation; but I was surprised that it worked! In this MR I added documentation to Note [Interesting dictionary arguments] to explain; and tests to ensure it stays fixed. - - - - - 11 changed files: - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Rules.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Types/Basic.hs - + testsuite/tests/simplCore/should_compile/T25703.hs - + testsuite/tests/simplCore/should_compile/T25703.stderr - + testsuite/tests/simplCore/should_compile/T25703a.hs - + testsuite/tests/simplCore/should_compile/T25703a.stderr - + testsuite/tests/simplCore/should_compile/T25965.hs - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Specialise.hs ===================================== @@ -1243,14 +1243,15 @@ specExpr env (Let bind body) -- Note [Fire rules in the specialiser] fireRewriteRules :: SpecEnv -> InExpr -> [OutExpr] -> (InExpr, [OutExpr]) fireRewriteRules env (Var f) args - | Just (rule, expr) <- specLookupRule env f args InitialPhase (getRules (se_rules env) f) + | let rules = getRules (se_rules env) f + , Just (rule, expr) <- specLookupRule env f args activeInInitialPhase rules , let rest_args = drop (ruleArity rule) args -- See Note [Extra args in the target] zapped_subst = Core.zapSubst (se_subst env) expr' = simpleOptExprWith defaultSimpleOpts zapped_subst expr -- simplOptExpr needed because lookupRule returns -- (\x y. rhs) arg1 arg2 - , (fun, args) <- collectArgs expr' - = fireRewriteRules env fun (args++rest_args) + , (fun', args') <- collectArgs expr' + = fireRewriteRules env fun' (args'++rest_args) fireRewriteRules _ fun args = (fun, args) -------------- @@ -1620,7 +1621,7 @@ specCalls :: Bool -- True => specialising imported fn -- This function checks existing rules, and does not create -- duplicate ones. So the caller does not need to do this filtering. --- See 'already_covered' +-- See `alreadyCovered` type SpecInfo = ( [CoreRule] -- Specialisation rules , [(Id,CoreExpr)] -- Specialised definition @@ -1644,15 +1645,13 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs = -- pprTrace "specCalls: some" (vcat -- [ text "function" <+> ppr fn - -- , text "calls:" <+> ppr calls_for_me - -- , text "subst" <+> ppr (se_subst env) ]) $ + -- , text "calls:" <+> ppr calls_for_me + -- , text "subst" <+> ppr (se_subst env) ]) $ foldlM spec_call ([], [], emptyUDs) calls_for_me | otherwise -- No calls or RHS doesn't fit our preconceptions - = warnPprTrace (not (exprIsTrivial rhs) && notNull calls_for_me && not (isClassOpId fn)) + = warnPprTrace (not (exprIsTrivial rhs) && notNull calls_for_me) "Missed specialisation opportunity for" (ppr fn $$ trace_doc) $ - -- isClassOpId: class-op Ids never inline; we specialise them - -- through fireRewriteRules. So don't complain about missed opportunities -- Note [Specialisation shape] -- pprTrace "specCalls: none" (ppr fn <+> ppr calls_for_me) $ return ([], [], emptyUDs) @@ -1664,6 +1663,10 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs fn_unf = realIdUnfolding fn -- Ignore loop-breaker-ness here inl_prag = idInlinePragma fn inl_act = inlinePragmaActivation inl_prag + is_active = isActive (beginPhase inl_act) :: Activation -> Bool + -- is_active: inl_act is the activation we are going to put in the new + -- SPEC rule; so we want to see if it is covered by another rule with + -- that same activation. is_local = isLocalId fn is_dfun = isDFunId fn dflags = se_dflags env @@ -1674,16 +1677,6 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs (rhs_bndrs, rhs_body) = collectBindersPushingCo rhs -- See Note [Account for casts in binding] - already_covered :: SpecEnv -> [CoreRule] -> [CoreExpr] -> Bool - already_covered env new_rules args -- Note [Specialisations already covered] - = isJust (specLookupRule env fn args (beginPhase inl_act) - (new_rules ++ existing_rules)) - -- Rules: we look both in the new_rules (generated by this invocation - -- of specCalls), and in existing_rules (passed in to specCalls) - -- inl_act: is the activation we are going to put in the new SPEC - -- rule; so we want to see if it is covered by another rule with - -- that same activation. - ---------------------------------------------------------- -- Specialise to one particular call pattern spec_call :: SpecInfo -- Accumulating parameter @@ -1717,8 +1710,12 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs -- , ppr dx_binds ]) $ -- return () + ; let all_rules = rules_acc ++ existing_rules + -- all_rules: we look both in the rules_acc (generated by this invocation + -- of specCalls), and in existing_rules (passed in to specCalls) ; if not useful -- No useful specialisation - || already_covered rhs_env2 rules_acc rule_lhs_args + || alreadyCovered rhs_env2 rule_bndrs fn rule_lhs_args is_active all_rules + -- See (SC1) in Note [Specialisations already covered] then return spec_acc else do { -- Run the specialiser on the specialised RHS @@ -1780,7 +1777,7 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs spec_fn_details = case idDetails fn of JoinId join_arity _ -> JoinId (join_arity - join_arity_decr) Nothing - DFunId is_nt -> DFunId is_nt + DFunId unary -> DFunId unary _ -> VanillaId ; spec_fn <- newSpecIdSM (idName fn) spec_fn_ty spec_fn_details spec_fn_info @@ -1804,6 +1801,8 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs , ppr spec_fn <+> dcolon <+> ppr spec_fn_ty , ppr rhs_bndrs, ppr call_args , ppr spec_rule + , text "acc" <+> ppr rules_acc + , text "existing" <+> ppr existing_rules ] ; -- pprTrace "spec_call: rule" _rule_trace_doc @@ -1812,19 +1811,35 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs , spec_uds `thenUDs` uds_acc ) } } +alreadyCovered :: SpecEnv + -> [Var] -> Id -> [CoreExpr] -- LHS of possible new rule + -> (Activation -> Bool) -- Which rules are active + -> [CoreRule] -> Bool +-- Note [Specialisations already covered] esp (SC2) +alreadyCovered env bndrs fn args is_active rules + = case specLookupRule env fn args is_active rules of + Nothing -> False + Just (rule, _) + | isAutoRule rule -> -- Discard identical rules + -- We know that (fn args) is an instance of RULE + -- Check if RULE is an instance of (fn args) + ruleLhsIsMoreSpecific in_scope bndrs args rule + | otherwise -> True -- User rules dominate + where + in_scope = substInScopeSet (se_subst env) + -- Convenience function for invoking lookupRule from Specialise -- The SpecEnv's InScopeSet should include all the Vars in the [CoreExpr] specLookupRule :: SpecEnv -> Id -> [CoreExpr] - -> CompilerPhase -- Look up rules as if we were in this phase + -> (Activation -> Bool) -- Which rules are active -> [CoreRule] -> Maybe (CoreRule, CoreExpr) -specLookupRule env fn args phase rules +specLookupRule env fn args is_active rules = lookupRule ropts in_scope_env is_active fn args rules where dflags = se_dflags env in_scope = substInScopeSet (se_subst env) in_scope_env = ISE in_scope (whenActiveUnfoldingFun is_active) ropts = initRuleOpts dflags - is_active = isActive phase {- Note [Specialising DFuns] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2323,21 +2338,24 @@ This plan is implemented in the Rec case of specBindItself. Note [Specialisations already covered] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We obviously don't want to generate two specialisations for the same -argument pattern. There are two wrinkles - -1. We do the already-covered test in specDefn, not when we generate -the CallInfo in mkCallUDs. We used to test in the latter place, but -we now iterate the specialiser somewhat, and the Id at the call site -might therefore not have all the RULES that we can see in specDefn - -2. What about two specialisations where the second is an *instance* -of the first? If the more specific one shows up first, we'll generate -specialisations for both. If the *less* specific one shows up first, -we *don't* currently generate a specialisation for the more specific -one. (See the call to lookupRule in already_covered.) Reasons: - (a) lookupRule doesn't say which matches are exact (bad reason) - (b) if the earlier specialisation is user-provided, it's - far from clear that we should auto-specialise further +argument pattern. Wrinkles + +(SC1) We do the already-covered test in specDefn, not when we generate + the CallInfo in mkCallUDs. We used to test in the latter place, but + we now iterate the specialiser somewhat, and the Id at the call site + might therefore not have all the RULES that we can see in specDefn + +(SC2) What about two specialisations where the second is an *instance* + of the first? It's a bit arbitrary, but here's what we do: + * If the existing one is user-specified, via a SPECIALISE pragma, we + suppress the further specialisation. + * If the existing one is auto-generated, we generate a second RULE + for the more specialised version. + The latter is important because we don't want the accidental order + of calls to determine what specialisations we generate. + +(SC3) Annoyingly, we /also/ eliminate duplicates in `filterCalls`. + See (MP3) in Note [Specialising polymorphic dictionaries] Note [Auto-specialisation and RULES] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2800,12 +2818,10 @@ non-dictionary bindings too. Note [Specialising polymorphic dictionaries] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Note June 2023: This has proved to be quite a tricky optimisation to get right see (#23469, #23109, #21229, #23445) so it is now guarded by a flag `-fpolymorphic-specialisation`. - Consider class M a where { foo :: a -> Int } @@ -2845,11 +2861,26 @@ Here are the moving parts: function. (MP3) If we have f :: forall m. Monoid m => blah, and two calls - (f @(Endo b) (d :: Monoid (Endo b)) - (f @(Endo (c->c)) (d :: Monoid (Endo (c->c))) + (f @(Endo b) (d1 :: Monoid (Endo b)) + (f @(Endo (c->c)) (d2 :: Monoid (Endo (c->c))) we want to generate a specialisation only for the first. The second is just a substitution instance of the first, with no greater specialisation. - Hence the call to `remove_dups` in `filterCalls`. + Hence the use of `removeDupCalls` in `filterCalls`. + + You might wonder if `d2` might be more specialised than `d1`; but no. + This `removeDupCalls` thing is at the definition site of `f`, and both `d1` + and `d2` are in scope. So `d1` is simply more polymorphic than `d2`, but + is just as specialised. + + This distinction is sadly lost once we build a RULE, so `alreadyCovered` + can't be so clever. E.g if we have an existing RULE + forall @a (d1:Ord Int) (d2: Eq a). f @a @Int d1 d2 = ... + and a putative new rule + forall (d1:Ord Int) (d2: Eq Int). f @Int @Int d1 d2 = ... + we /don't/ want the existing rule to subsume the new one. + + So we sadly put up with having two rather different places where we + eliminate duplicates: `alreadyCovered` and `removeDupCalls`. All this arose in #13873, in the unexpected form that a SPECIALISE pragma made the program slower! The reason was that the specialised @@ -2947,16 +2978,29 @@ data CallInfoSet = CIS Id (Bag CallInfo) -- The list of types and dictionaries is guaranteed to -- match the type of f -- The Bag may contain duplicate calls (i.e. f @T and another f @T) - -- These dups are eliminated by already_covered in specCalls + -- These dups are eliminated by alreadyCovered in specCalls data CallInfo - = CI { ci_key :: [SpecArg] -- All arguments + = CI { ci_key :: [SpecArg] -- Arguments of the call + -- See Note [The (CI-KEY) invariant] + , ci_fvs :: IdSet -- Free Ids of the ci_key call -- /not/ including the main id itself, of course -- NB: excluding tyvars: -- See Note [Specialising polymorphic dictionaries] } +{- Note [The (CI-KEY) invariant] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Invariant (CI-KEY): + In the `ci_key :: [SpecArg]` field of `CallInfo`, + * The list is non-empty + * The least element is always a `SpecDict` + +In this way the RULE has as few args as possible, which broadens its +applicability, since rules only fire when saturated. +-} + type DictExpr = CoreExpr ciSetFilter :: (CallInfo -> Bool) -> CallInfoSet -> CallInfoSet @@ -3045,10 +3089,7 @@ mkCallUDs' env f args ci_key :: [SpecArg] ci_key = dropWhileEndLE (not . isSpecDict) $ zipWith mk_spec_arg args pis - -- Drop trailing args until we get to a SpecDict - -- In this way the RULE has as few args as possible, - -- which broadens its applicability, since rules only - -- fire when saturated + -- Establish (CI-KEY): drop trailing args until we get to a SpecDict mk_spec_arg :: OutExpr -> PiTyBinder -> SpecArg mk_spec_arg arg (Named bndr) @@ -3086,34 +3127,76 @@ site, so we only look through ticks that RULE matching looks through -} wantCallsFor :: SpecEnv -> Id -> Bool -wantCallsFor _env _f = True - -- We could reduce the size of the UsageDetails by being less eager - -- about collecting calls for LocalIds: there is no point for - -- ones that are lambda-bound. We can't decide this by looking at - -- the (absence of an) unfolding, because unfoldings for local - -- functions are discarded by cloneBindSM, so no local binder will - -- have an unfolding at this stage. We'd have to keep a candidate - -- set of let-binders. - -- - -- Not many lambda-bound variables have dictionary arguments, so - -- this would make little difference anyway. - -- - -- For imported Ids we could check for an unfolding, but we have to - -- do so anyway in canSpecImport, and it seems better to have it - -- all in one place. So we simply collect usage info for imported - -- overloaded functions. - -{- Note [Interesting dictionary arguments] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Consider this - \a.\d:Eq a. let f = ... in ...(f d)... -There really is not much point in specialising f wrt the dictionary d, -because the code for the specialised f is not improved at all, because -d is lambda-bound. We simply get junk specialisations. - -What is "interesting"? Just that it has *some* structure. But what about -variables? We look in the variable's /unfolding/. And that means -that we must be careful to ensure that dictionaries have unfoldings, +-- See Note [wantCallsFor] +wantCallsFor _env f + = case idDetails f of + RecSelId {} -> False + DataConWorkId {} -> False + DataConWrapId {} -> False + ClassOpId {} -> False + PrimOpId {} -> False + FCallId {} -> False + TickBoxOpId {} -> False + CoVarId {} -> False + + DFunId {} -> True + VanillaId {} -> True + JoinId {} -> True + WorkerLikeId {} -> True + RepPolyId {} -> True + +{- Note [wantCallsFor] +~~~~~~~~~~~~~~~~~~~~~~ +`wantCallsFor env f` says whether the Specialiser should collect calls for +function `f`; other thing being equal, the fewer calls we collect the better. It +is False for things we can't specialise: + +* ClassOpId: never inline and we don't have a defn to specialise; we specialise + them through fireRewriteRules. +* PrimOpId: are never overloaded +* Data constructors: we never specialise them + +We could reduce the size of the UsageDetails by being less eager about +collecting calls for some LocalIds: there is no point for ones that are +lambda-bound. We can't decide this by looking at the (absence of an) unfolding, +because unfoldings for local functions are discarded by cloneBindSM, so no local +binder will have an unfolding at this stage. We'd have to keep a candidate set +of let-binders. + +Not many lambda-bound variables have dictionary arguments, so this would make +little difference anyway. + +For imported Ids we could check for an unfolding, but we have to do so anyway in +canSpecImport, and it seems better to have it all in one place. So we simply +collect usage info for imported overloaded functions. + +Note [Interesting dictionary arguments] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In `mkCallUDs` we only use `SpecDict` for dictionaries of which +`interestingDict` holds. Otherwise we use `UnspecArg`. Two reasons: + +* Consider this + \a.\d:Eq a. let f = ... in ...(f d)... + There really is not much point in specialising f wrt the dictionary d, + because the code for the specialised f is not improved at all, because + d is lambda-bound. We simply get junk specialisations. + +* Consider this (#25703): + f :: (Eq a, Show b) => a -> b -> INt + goo :: forall x. (Eq x) => x -> blah + goo @x (d:Eq x) (arg:x) = ...(f @x @Int d $fShowInt)... + If we built a `ci_key` with a (SpecDict d) for `d`, we would end up + discarding the call at the `\d`. But if we use `UnspecArg` for that + uninteresting `d`, we'll get a `ci_key` of + f @x @Int UnspecArg (SpecDict $fShowInt) + and /that/ can float out to f's definition and specialise nicely. + Hooray. (NB: the call can float only if `-fpolymorphic-specialisation` + is on; otherwise it'll be trapped by the `\@x -> ...`.)( + +What is "interesting"? (See `interestingDict`.) Just that it has *some* +structure. But what about variables? We look in the variable's /unfolding/. +And that means that we must be careful to ensure that dictionaries /have/ +unfoldings, * cloneBndrSM discards non-Stable unfoldings * specBind updates the unfolding after specialisation @@ -3159,7 +3242,7 @@ Now `f` turns into: meth @a dc .... When we specialise `f`, at a=Int say, that superclass selection can -nfire (via rewiteClassOps), but that info (that 'dc' is now a +fire (via rewiteClassOps), but that info (that 'dc' is now a particular dictionary `C`, of type `C Int`) must be available to the call `meth @a dc`, so that we can fire the `meth` class-op, and thence specialise `wombat`. @@ -3286,7 +3369,11 @@ dumpUDs :: [CoreBndr] -> UsageDetails -> (UsageDetails, OrdList DictBind) -- Used at a lambda or case binder; just dump anything mentioning the binder dumpUDs bndrs uds@(MkUD { ud_binds = orig_dbs, ud_calls = orig_calls }) | null bndrs = (uds, nilOL) -- Common in case alternatives - | otherwise = -- pprTrace "dumpUDs" (ppr bndrs $$ ppr free_uds $$ ppr dump_dbs) $ + | otherwise = -- pprTrace "dumpUDs" (vcat + -- [ text "bndrs" <+> ppr bndrs + -- , text "uds" <+> ppr uds + -- , text "free_uds" <+> ppr free_uds + -- , text "dump-dbs" <+> ppr dump_dbs ]) $ (free_uds, dump_dbs) where free_uds = uds { ud_binds = free_dbs, ud_calls = free_calls } @@ -3325,20 +3412,17 @@ callsForMe fn uds@MkUD { ud_binds = orig_dbs, ud_calls = orig_calls } calls_for_me = case lookupDVarEnv orig_calls fn of Nothing -> [] Just cis -> filterCalls cis orig_dbs - -- filterCalls: drop calls that (directly or indirectly) - -- refer to fn. See Note [Avoiding loops (DFuns)] ---------------------- filterCalls :: CallInfoSet -> FloatedDictBinds -> [CallInfo] --- Remove dominated calls (Note [Specialising polymorphic dictionaries]) --- and loopy DFuns (Note [Avoiding loops (DFuns)]) +-- Remove +-- (a) dominated calls: (MP3) in Note [Specialising polymorphic dictionaries] +-- (b) loopy DFuns: Note [Avoiding loops (DFuns)] filterCalls (CIS fn call_bag) (FDB { fdb_binds = dbs }) - | isDFunId fn -- Note [Avoiding loops (DFuns)] applies only to DFuns - = filter ok_call de_dupd_calls - | otherwise -- Do not apply it to non-DFuns - = de_dupd_calls -- See Note [Avoiding loops (non-DFuns)] + | isDFunId fn = filter ok_call de_dupd_calls -- Deals with (b) + | otherwise = de_dupd_calls where - de_dupd_calls = remove_dups call_bag + de_dupd_calls = removeDupCalls call_bag -- Deals with (a) dump_set = foldl' go (unitVarSet fn) dbs -- This dump-set could also be computed by splitDictBinds @@ -3352,10 +3436,10 @@ filterCalls (CIS fn call_bag) (FDB { fdb_binds = dbs }) ok_call (CI { ci_fvs = fvs }) = fvs `disjointVarSet` dump_set -remove_dups :: Bag CallInfo -> [CallInfo] +removeDupCalls :: Bag CallInfo -> [CallInfo] -- Calls involving more generic instances beat more specific ones. -- See (MP3) in Note [Specialising polymorphic dictionaries] -remove_dups calls = foldr add [] calls +removeDupCalls calls = foldr add [] calls where add :: CallInfo -> [CallInfo] -> [CallInfo] add ci [] = [ci] @@ -3364,12 +3448,20 @@ remove_dups calls = foldr add [] calls | otherwise = ci2 : add ci1 cis beats_or_same :: CallInfo -> CallInfo -> Bool +-- (beats_or_same ci1 ci2) is True if specialising on ci1 subsumes ci2 +-- That is: ci1's types are less specialised than ci2 +-- ci1 specialises on the same dict args as ci2 beats_or_same (CI { ci_key = args1 }) (CI { ci_key = args2 }) = go args1 args2 where - go [] _ = True + go [] [] = True go (arg1:args1) (arg2:args2) = go_arg arg1 arg2 && go args1 args2 - go (_:_) [] = False + + -- If one or the other runs dry, the other must still have a SpecDict + -- because of the (CI-KEY) invariant. So neither subsumes the other; + -- one is more specialised (faster code) but the other is more generally + -- applicable. + go _ _ = False go_arg (SpecType ty1) (SpecType ty2) = isJust (tcMatchTy ty1 ty2) go_arg UnspecType UnspecType = True ===================================== compiler/GHC/Core/Rules.hs ===================================== @@ -9,7 +9,7 @@ -- The 'CoreRule' datatype itself is declared elsewhere. module GHC.Core.Rules ( -- ** Looking up rules - lookupRule, matchExprs, + lookupRule, matchExprs, ruleLhsIsMoreSpecific, -- ** RuleBase, RuleEnv RuleBase, RuleEnv(..), mkRuleEnv, emptyRuleEnv, @@ -587,8 +587,8 @@ findBest :: InScopeSet -> (Id, [CoreExpr]) findBest _ _ (rule,ans) [] = (rule,ans) findBest in_scope target (rule1,ans1) ((rule2,ans2):prs) - | isMoreSpecific in_scope rule1 rule2 = findBest in_scope target (rule1,ans1) prs - | isMoreSpecific in_scope rule2 rule1 = findBest in_scope target (rule2,ans2) prs + | ruleIsMoreSpecific in_scope rule1 rule2 = findBest in_scope target (rule1,ans1) prs + | ruleIsMoreSpecific in_scope rule2 rule1 = findBest in_scope target (rule2,ans2) prs | debugIsOn = let pp_rule rule = ifPprDebug (ppr rule) (doubleQuotes (ftext (ruleName rule))) @@ -603,15 +603,25 @@ findBest in_scope target (rule1,ans1) ((rule2,ans2):prs) where (fn,args) = target -isMoreSpecific :: InScopeSet -> CoreRule -> CoreRule -> Bool --- The call (rule1 `isMoreSpecific` rule2) +ruleIsMoreSpecific :: InScopeSet -> CoreRule -> CoreRule -> Bool +-- The call (rule1 `ruleIsMoreSpecific` rule2) -- sees if rule2 can be instantiated to look like rule1 --- See Note [isMoreSpecific] -isMoreSpecific _ (BuiltinRule {}) _ = False -isMoreSpecific _ (Rule {}) (BuiltinRule {}) = True -isMoreSpecific in_scope (Rule { ru_bndrs = bndrs1, ru_args = args1 }) - (Rule { ru_bndrs = bndrs2, ru_args = args2 }) - = isJust (matchExprs in_scope_env bndrs2 args2 args1) +-- See Note [ruleIsMoreSpecific] +ruleIsMoreSpecific in_scope rule1 rule2 + = case rule1 of + BuiltinRule {} -> False + Rule { ru_bndrs = bndrs1, ru_args = args1 } + -> ruleLhsIsMoreSpecific in_scope bndrs1 args1 rule2 + +ruleLhsIsMoreSpecific :: InScopeSet + -> [Var] -> [CoreExpr] -- LHS of a possible new rule + -> CoreRule -- An existing rule + -> Bool -- New one is more specific +ruleLhsIsMoreSpecific in_scope bndrs1 args1 rule2 + = case rule2 of + BuiltinRule {} -> True + Rule { ru_bndrs = bndrs2, ru_args = args2 } + -> isJust (matchExprs in_scope_env bndrs2 args2 args1) where full_in_scope = in_scope `extendInScopeSetList` bndrs1 in_scope_env = ISE full_in_scope noUnfoldingFun @@ -620,9 +630,9 @@ isMoreSpecific in_scope (Rule { ru_bndrs = bndrs1, ru_args = args1 }) noBlackList :: Activation -> Bool noBlackList _ = False -- Nothing is black listed -{- Note [isMoreSpecific] +{- Note [ruleIsMoreSpecific] ~~~~~~~~~~~~~~~~~~~~~~~~ -The call (rule1 `isMoreSpecific` rule2) +The call (rule1 `ruleIsMoreSpecific` rule2) sees if rule2 can be instantiated to look like rule1. Wrinkle: @@ -825,7 +835,7 @@ bound on the LHS: The rule looks like forall (a::*) (d::Eq Char) (x :: Foo a Char). - f (Foo a Char) d x = True + f @(Foo a Char) d x = True Matching the rule won't bind 'a', and legitimately so. We fudge by pretending that 'a' is bound to (Any :: *). ===================================== compiler/GHC/Core/Unify.hs ===================================== @@ -331,35 +331,57 @@ Wrinkles `DontBindMe`, the unifier must return `SurelyApart`, not `MaybeApart`. See `go_fam` in `uVarOrFam` -(ATF6) You might think that when /matching/ the um_fam_env will always be empty, - because type-class-instance and type-family-instance heads can't include type - families. E.g. instance C (F a) where ... -- Illegal - - But you'd be wrong: when "improving" type family constraint we may have a - type family on the LHS of a match. Consider +(ATF6) When /matching/ can we ever have a type-family application on the LHS, in + the template? You might think not, because type-class-instance and + type-family-instance heads can't include type families. E.g. + instance C (F a) where ... -- Illegal + + But you'd be wrong: even when matching, we can see type families in the LHS template: + * In `checkValidClass`, in `check_dm` we check that the default method has the + right type, using matching, both ways. And that type may have type-family + applications in it. Example in test CoOpt_Singletons. + + * In the specialiser: see the call to `tcMatchTy` in + `GHC.Core.Opt.Specialise.beats_or_same` + + * With -fpolymorphic-specialsation, we might get a specialiation rule like + RULE forall a (d :: Eq (Maybe (F a))) . + f @(Maybe (F a)) d = ... + See #25965. + + * A user-written RULE could conceivably have a type-family application + in the template. It might not be a good rule, but I don't think we currently + check for this. + + In all these cases we are only interested in finding a substitution /for + type variables/ that makes the match work. So we simply want to recurse into + the arguments of the type family. E.g. + Template: forall a. Maybe (F a) + Target: Mabybe (F Int) + We want to succeed with substitution [a :-> Int]. See (ATF9). + + Conclusion: where we enter via `tcMatchTy`, `tcMatchTys`, `tc_match_tys`, + etc, we always end up in `tc_match_tys_x`. There we invoke the unifier + but we do not distinguish between `SurelyApart` and `MaybeApart`. So in + these cases we can set `um_bind_fam_fun` to `neverBindFam`. + +(ATF7) There is one other, very special case of matching where we /do/ want to + bind type families in `um_fam_env`, namely in GHC.Tc.Solver.Equality, the call + to `tcUnifyTyForInjectivity False` in `improve_injective_wanted_top`. + Consider + of a match. Consider type family G6 a = r | r -> a type instance G6 [a] = [G a] type instance G6 Bool = Int - and the Wanted constraint [W] G6 alpha ~ [Int]. We /match/ each type instance - RHS against [Int]! So we try - [G a] ~ [Int] + and suppose we haev a Wanted constraint + [W] G6 alpha ~ [Int] +. According to Section 5.2 of "Injective type families for Haskell", we /match/ + the RHS each type instance [Int]. So we try + Template: [G a] Target: [Int] and we want to succeed with MaybeApart, so that we can generate the improvement - constraint [W] alpha ~ [beta] where beta is fresh. - See Section 5.2 of "Injective type families for Haskell". - - A second place that we match with type-fams on the LHS is in `checkValidClass`. - In `check_dm` we check that the default method has the right type, using matching, - both ways. And that type may have type-family applications in it. Example in - test CoOpt_Singletons. - -(ATF7) You might think that (ATF6) is a very special case, and in /other/ uses of - matching, where we enter via `tc_match_tys_x` we will never see a type-family - in the template. But actually we do see that case in the specialiser: see - the call to `tcMatchTy` in `GHC.Core.Opt.Specialise.beats_or_same` - - Also: a user-written RULE could conceivably have a type-family application - in the template. It might not be a good rule, but I don't think we currently - check for this. + constraint + [W] alpha ~ [beta] + where beta is fresh. We do this by binding [G a :-> Int] (ATF8) The treatment of type families is governed by um_bind_fam_fun :: BindFamFun @@ -399,6 +421,8 @@ Wrinkles Key point: when decomposing (F tys1 ~ F tys2), we should /also/ extend the type-family substitution. + (ATF11-1) All this cleverness only matters when unifying, not when matching + (ATF12) There is a horrid exception for the injectivity check. See (UR1) in in Note [Specification of unification]. @@ -595,7 +619,7 @@ tc_match_tys_x :: HasDebugCallStack -> [Type] -> Maybe Subst tc_match_tys_x bind_tv match_kis (Subst in_scope id_env tv_env cv_env) tys1 tys2 - = case tc_unify_tys alwaysBindFam -- (ATF7) in Note [Apartness and type families] + = case tc_unify_tys neverBindFam -- (ATF7) in Note [Apartness and type families] bind_tv False -- Matching, not unifying False -- Not an injectivity check @@ -1857,6 +1881,7 @@ uVarOrFam env ty1 ty2 kco = go_fam_fam tc1 tys1 tys2 kco -- Now check if we can bind the (F tys) to the RHS + -- This can happen even when matching: see (ATF7) | BindMe <- um_bind_fam_fun env tc1 tys1 rhs = -- ToDo: do we need an occurs check here? do { extendFamEnv tc1 tys1 rhs @@ -1881,11 +1906,6 @@ uVarOrFam env ty1 ty2 kco -- go_fam_fam: LHS and RHS are both saturated type-family applications, -- for the same type-family F go_fam_fam tc tys1 tys2 kco - | tcEqTyConAppArgs tys1 tys2 - -- Detect (F tys ~ F tys); otherwise we'd build an infinite substitution - = return () - - | otherwise -- Decompose (F tys1 ~ F tys2): (ATF9) -- Use injectivity information of F: (ATF10) -- But first bind the type-fam if poss: (ATF11) @@ -1902,13 +1922,19 @@ uVarOrFam env ty1 ty2 kco (inj_tys1, noninj_tys1) = partitionByList inj tys1 (inj_tys2, noninj_tys2) = partitionByList inj tys2 - bind_fam_if_poss | BindMe <- um_bind_fam_fun env tc tys1 rhs1 - = extendFamEnv tc tys1 rhs1 - | um_unif env - , BindMe <- um_bind_fam_fun env tc tys2 rhs2 - = extendFamEnv tc tys2 rhs2 - | otherwise - = return () + bind_fam_if_poss + | not (um_unif env) -- Not when matching (ATF11-1) + = return () + | tcEqTyConAppArgs tys1 tys2 -- Detect (F tys ~ F tys); + = return () -- otherwise we'd build an infinite substitution + | BindMe <- um_bind_fam_fun env tc tys1 rhs1 + = extendFamEnv tc tys1 rhs1 + | um_unif env + , BindMe <- um_bind_fam_fun env tc tys2 rhs2 + = extendFamEnv tc tys2 rhs2 + | otherwise + = return () + rhs1 = mkTyConApp tc tys2 `mkCastTy` mkSymCo kco rhs2 = mkTyConApp tc tys1 `mkCastTy` kco @@ -1993,7 +2019,7 @@ data UMState = UMState -- in um_foralls; i.e. variables bound by foralls inside the types being unified -- When /matching/ um_fam_env is usually empty; but not quite always. - -- See (ATF6) and (ATF7) of Note [Apartness and type families] + -- See (ATF7) of Note [Apartness and type families] newtype UM a = UM' { unUM :: UMState -> UnifyResultM (UMState, a) } ===================================== compiler/GHC/Tc/Solver/Equality.hs ===================================== @@ -3017,6 +3017,7 @@ improve_wanted_top_fun_eqs fam_tc lhs_tys rhs_ty improve_injective_wanted_top :: FamInstEnvs -> [Bool] -> TyCon -> [TcType] -> Xi -> TcS [TypeEqn] -- Interact with top-level instance declarations +-- See Section 5.2 in the Injective Type Families paper improve_injective_wanted_top fam_envs inj_args fam_tc lhs_tys rhs_ty = concatMapM do_one branches where @@ -3035,6 +3036,7 @@ improve_injective_wanted_top fam_envs inj_args fam_tc lhs_tys rhs_ty do_one branch@(CoAxBranch { cab_tvs = branch_tvs, cab_lhs = branch_lhs_tys, cab_rhs = branch_rhs }) | let in_scope1 = in_scope `extendInScopeSetList` branch_tvs , Just subst <- tcUnifyTyForInjectivity False in_scope1 branch_rhs rhs_ty + -- False: matching, not unifying = do { let inSubst tv = tv `elemVarEnv` getTvSubstEnv subst unsubstTvs = filterOut inSubst branch_tvs -- The order of unsubstTvs is important; it must be ===================================== compiler/GHC/Types/Basic.hs ===================================== @@ -85,7 +85,7 @@ module GHC.Types.Basic ( CompilerPhase(..), PhaseNum, beginPhase, nextPhase, laterPhase, Activation(..), isActive, competesWith, - isNeverActive, isAlwaysActive, activeInFinalPhase, + isNeverActive, isAlwaysActive, activeInFinalPhase, activeInInitialPhase, activateAfterInitial, activateDuringFinal, activeAfter, RuleMatchInfo(..), isConLike, isFunLike, ===================================== testsuite/tests/simplCore/should_compile/T25703.hs ===================================== @@ -0,0 +1,7 @@ +module T25703 where + +f :: (Eq a, Show b) => a -> b -> Int +f x y = f x y + +goo :: forall x. (Eq x) => x -> Int +goo arg = f arg (3::Int) ===================================== testsuite/tests/simplCore/should_compile/T25703.stderr ===================================== @@ -0,0 +1,2 @@ +Rule fired: SPEC f @_ @Int (T25703) +Rule fired: SPEC f @_ @Int (T25703) ===================================== testsuite/tests/simplCore/should_compile/T25703a.hs ===================================== @@ -0,0 +1,69 @@ +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE GADTs #-} + +{-# OPTIONS_GHC -O2 -fspecialise-aggressively #-} + +-- This pragma is just here to pretend that the function body of 'foo' is huge +-- and should never be inlined. +{-# OPTIONS_GHC -funfolding-use-threshold=-200 #-} + +module T25703a where + +import Data.Kind +import Data.Type.Equality +import Data.Proxy +import GHC.TypeNats + +-- Pretend this is some big dictionary that absolutely must get +-- specialised away for performance reasons. +type C :: Nat -> Constraint +class C i where + meth :: Proxy i -> Double +instance C 0 where + meth _ = 0.1 +instance C 1 where + meth _ = 1.1 +instance C 2 where + meth _ = 2.1 + +{-# INLINEABLE foo #-} +foo :: forall a (n :: Nat) (m :: Nat) + . ( Eq a, C n, C m ) + => a -> ( Proxy n, Proxy m ) -> Int -> Double +-- Pretend this is a big complicated function, too big to inline, +-- for which we absolutely must specialise away the 'C n', 'C m' +-- dictionaries for performance reasons. +foo a b c + = if a == a + then meth @n Proxy + fromIntegral c + else 2 * meth @m Proxy + +-- Runtime dispatch to a specialisation of 'foo' +foo_spec :: forall a (n :: Nat) (m :: Nat) + . ( Eq a, KnownNat n, KnownNat m ) + => a -> ( Proxy n, Proxy m ) -> Int -> Double +foo_spec a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @0 Proxy Proxy + = foo @a @0 @0 a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @1 Proxy Proxy + = foo @a @0 @1 a b c + | Just Refl <- sameNat @n @1 Proxy Proxy + , Just Refl <- sameNat @m @1 Proxy Proxy + = foo @a @1 @1 a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @0 @2 a b c + | Just Refl <- sameNat @n @1 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @1 @2 a b c + | Just Refl <- sameNat @n @2 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @2 @2 a b c + | otherwise + = error $ unlines + [ "f: no specialisation" + , "n: " ++ show (natVal @n Proxy) + , "m: " ++ show (natVal @m Proxy) + ] ===================================== testsuite/tests/simplCore/should_compile/T25703a.stderr ===================================== @@ -0,0 +1,6 @@ +Rule fired: SPEC foo @_ @2 @2 (T25703a) +Rule fired: SPEC foo @_ @1 @2 (T25703a) +Rule fired: SPEC foo @_ @0 @2 (T25703a) +Rule fired: SPEC foo @_ @1 @1 (T25703a) +Rule fired: SPEC foo @_ @0 @1 (T25703a) +Rule fired: SPEC foo @_ @0 @0 (T25703a) ===================================== testsuite/tests/simplCore/should_compile/T25965.hs ===================================== @@ -0,0 +1,18 @@ +{-# LANGUAGE TypeFamilies #-} +{-# OPTIONS_GHC -O -fpolymorphic-specialisation #-} + +module Foo where + +type family F a + +data T a = T1 + +instance Eq (T a) where { (==) x y = False } + +foo :: Eq a => a -> Bool +foo x | x==x = True + | otherwise = foo x + +bar :: forall b. b -> T (F b) -> Bool +bar y x = foo x + ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -535,3 +535,6 @@ test('T25197', [req_th, extra_files(["T25197_TH.hs"]), only_ways(['optasm'])], m test('T25389', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dno-typeable-binds']) test('T24359a', normal, compile, ['-O -ddump-rules']) test('T25713', [grep_errmsg('W:::')], compile, ['-O -ddump-simpl']) +test('T25965', normal, compile, ['-O']) +test('T25703', [grep_errmsg(r'SPEC')], compile, ['-O -fpolymorphic-specialisation -ddump-rule-firings']) +test('T25703a', [grep_errmsg(r'SPEC')], compile, ['-O -fpolymorphic-specialisation -ddump-rule-firings']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3909c6899e6fb7fd95f60c73cc25f47… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3909c6899e6fb7fd95f60c73cc25f47… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T25965] Fix infelicities in the Specialiser
by Simon Peyton Jones (＠simonpj) 17 Apr '25

17 Apr '25

Simon Peyton Jones pushed to branch wip/T25965 at Glasgow Haskell Compiler / GHC Commits: 241c93c0 by Simon Peyton Jones at 2025-04-17T09:03:24+01:00 Fix infelicities in the Specialiser On the way to #23109 (unary classes) I discovered some infelicities (or maybe tiny bugs, I forget) in the type-class specialiser. I also tripped over #25965, an outright bug in the rule matcher Specifically: * Refactor: I enhanced `wantCallsFor`, whih previously always said `True`, to discard calls of class-ops, data constructors etc. This is a bit more efficient; and it means we don't need to worry about filtering them out later. * Fix: I tidied up some tricky logic that eliminated redundant specialisations. It wasn't working correctly. See the expanded Note [Specialisations already covered], and (MP3) in Note [Specialising polymorphic dictionaries]. See also the new top-level `alreadyCovered` function, which now goes via `GHC.Core.Rules.ruleLhsIsMoreSpecific` I also added a useful Note [The (CI-KEY) invariant] * Fix #25965: fixed a tricky bug in the `go_fam_fam` in `GHC.Core.Unify.uVarOrFam`, which allows matching to succeed without binding all type varibles. I enhanced Note [Apartness and type families] some more * #25703. This ticket "just works" with -fpolymorphic-specialisation; but I was surprised that it worked! In this MR I added documentation to Note [Interesting dictionary arguments] to explain; and tests to ensure it stays fixed. - - - - - 11 changed files: - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Rules.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Types/Basic.hs - + testsuite/tests/simplCore/should_compile/T25703.hs - + testsuite/tests/simplCore/should_compile/T25703.stderr - + testsuite/tests/simplCore/should_compile/T25703a.hs - + testsuite/tests/simplCore/should_compile/T25703a.stderr - + testsuite/tests/simplCore/should_compile/T25965.hs - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Specialise.hs ===================================== @@ -1243,14 +1243,15 @@ specExpr env (Let bind body) -- Note [Fire rules in the specialiser] fireRewriteRules :: SpecEnv -> InExpr -> [OutExpr] -> (InExpr, [OutExpr]) fireRewriteRules env (Var f) args - | Just (rule, expr) <- specLookupRule env f args InitialPhase (getRules (se_rules env) f) + | let rules = getRules (se_rules env) f + , Just (rule, expr) <- specLookupRule env f args activeInInitialPhase rules , let rest_args = drop (ruleArity rule) args -- See Note [Extra args in the target] zapped_subst = Core.zapSubst (se_subst env) expr' = simpleOptExprWith defaultSimpleOpts zapped_subst expr -- simplOptExpr needed because lookupRule returns -- (\x y. rhs) arg1 arg2 - , (fun, args) <- collectArgs expr' - = fireRewriteRules env fun (args++rest_args) + , (fun', args') <- collectArgs expr' + = fireRewriteRules env fun' (args'++rest_args) fireRewriteRules _ fun args = (fun, args) -------------- @@ -1620,7 +1621,7 @@ specCalls :: Bool -- True => specialising imported fn -- This function checks existing rules, and does not create -- duplicate ones. So the caller does not need to do this filtering. --- See 'already_covered' +-- See `alreadyCovered` type SpecInfo = ( [CoreRule] -- Specialisation rules , [(Id,CoreExpr)] -- Specialised definition @@ -1644,15 +1645,13 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs = -- pprTrace "specCalls: some" (vcat -- [ text "function" <+> ppr fn - -- , text "calls:" <+> ppr calls_for_me - -- , text "subst" <+> ppr (se_subst env) ]) $ + -- , text "calls:" <+> ppr calls_for_me + -- , text "subst" <+> ppr (se_subst env) ]) $ foldlM spec_call ([], [], emptyUDs) calls_for_me | otherwise -- No calls or RHS doesn't fit our preconceptions - = warnPprTrace (not (exprIsTrivial rhs) && notNull calls_for_me && not (isClassOpId fn)) + = warnPprTrace (not (exprIsTrivial rhs) && notNull calls_for_me) "Missed specialisation opportunity for" (ppr fn $$ trace_doc) $ - -- isClassOpId: class-op Ids never inline; we specialise them - -- through fireRewriteRules. So don't complain about missed opportunities -- Note [Specialisation shape] -- pprTrace "specCalls: none" (ppr fn <+> ppr calls_for_me) $ return ([], [], emptyUDs) @@ -1664,6 +1663,10 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs fn_unf = realIdUnfolding fn -- Ignore loop-breaker-ness here inl_prag = idInlinePragma fn inl_act = inlinePragmaActivation inl_prag + is_active = isActive (beginPhase inl_act) :: Activation -> Bool + -- is_active: inl_act is the activation we are going to put in the new + -- SPEC rule; so we want to see if it is covered by another rule with + -- that same activation. is_local = isLocalId fn is_dfun = isDFunId fn dflags = se_dflags env @@ -1674,16 +1677,6 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs (rhs_bndrs, rhs_body) = collectBindersPushingCo rhs -- See Note [Account for casts in binding] - already_covered :: SpecEnv -> [CoreRule] -> [CoreExpr] -> Bool - already_covered env new_rules args -- Note [Specialisations already covered] - = isJust (specLookupRule env fn args (beginPhase inl_act) - (new_rules ++ existing_rules)) - -- Rules: we look both in the new_rules (generated by this invocation - -- of specCalls), and in existing_rules (passed in to specCalls) - -- inl_act: is the activation we are going to put in the new SPEC - -- rule; so we want to see if it is covered by another rule with - -- that same activation. - ---------------------------------------------------------- -- Specialise to one particular call pattern spec_call :: SpecInfo -- Accumulating parameter @@ -1717,8 +1710,12 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs -- , ppr dx_binds ]) $ -- return () + ; let all_rules = rules_acc ++ existing_rules + -- all_rules: we look both in the rules_acc (generated by this invocation + -- of specCalls), and in existing_rules (passed in to specCalls) ; if not useful -- No useful specialisation - || already_covered rhs_env2 rules_acc rule_lhs_args + || alreadyCovered rhs_env2 rule_bndrs fn rule_lhs_args is_active all_rules + -- See (SC1) in Note [Specialisations already covered] then return spec_acc else do { -- Run the specialiser on the specialised RHS @@ -1780,7 +1777,7 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs spec_fn_details = case idDetails fn of JoinId join_arity _ -> JoinId (join_arity - join_arity_decr) Nothing - DFunId is_nt -> DFunId is_nt + DFunId unary -> DFunId unary _ -> VanillaId ; spec_fn <- newSpecIdSM (idName fn) spec_fn_ty spec_fn_details spec_fn_info @@ -1804,6 +1801,8 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs , ppr spec_fn <+> dcolon <+> ppr spec_fn_ty , ppr rhs_bndrs, ppr call_args , ppr spec_rule + , text "acc" <+> ppr rules_acc + , text "existing" <+> ppr existing_rules ] ; -- pprTrace "spec_call: rule" _rule_trace_doc @@ -1812,19 +1811,35 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs , spec_uds `thenUDs` uds_acc ) } } +alreadyCovered :: SpecEnv + -> [Var] -> Id -> [CoreExpr] -- LHS of possible new rule + -> (Activation -> Bool) -- Which rules are active + -> [CoreRule] -> Bool +-- Note [Specialisations already covered] esp (SC2) +alreadyCovered env bndrs fn args is_active rules + = case specLookupRule env fn args is_active rules of + Nothing -> False + Just (rule, _) + | isAutoRule rule -> -- Discard identical rules + -- We know that (fn args) is an instance of RULE + -- Check if RULE is an instance of (fn args) + ruleLhsIsMoreSpecific in_scope bndrs args rule + | otherwise -> True -- User rules dominate + where + in_scope = substInScopeSet (se_subst env) + -- Convenience function for invoking lookupRule from Specialise -- The SpecEnv's InScopeSet should include all the Vars in the [CoreExpr] specLookupRule :: SpecEnv -> Id -> [CoreExpr] - -> CompilerPhase -- Look up rules as if we were in this phase + -> (Activation -> Bool) -- Which rules are active -> [CoreRule] -> Maybe (CoreRule, CoreExpr) -specLookupRule env fn args phase rules +specLookupRule env fn args is_active rules = lookupRule ropts in_scope_env is_active fn args rules where dflags = se_dflags env in_scope = substInScopeSet (se_subst env) in_scope_env = ISE in_scope (whenActiveUnfoldingFun is_active) ropts = initRuleOpts dflags - is_active = isActive phase {- Note [Specialising DFuns] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2323,21 +2338,24 @@ This plan is implemented in the Rec case of specBindItself. Note [Specialisations already covered] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We obviously don't want to generate two specialisations for the same -argument pattern. There are two wrinkles - -1. We do the already-covered test in specDefn, not when we generate -the CallInfo in mkCallUDs. We used to test in the latter place, but -we now iterate the specialiser somewhat, and the Id at the call site -might therefore not have all the RULES that we can see in specDefn - -2. What about two specialisations where the second is an *instance* -of the first? If the more specific one shows up first, we'll generate -specialisations for both. If the *less* specific one shows up first, -we *don't* currently generate a specialisation for the more specific -one. (See the call to lookupRule in already_covered.) Reasons: - (a) lookupRule doesn't say which matches are exact (bad reason) - (b) if the earlier specialisation is user-provided, it's - far from clear that we should auto-specialise further +argument pattern. Wrinkles + +(SC1) We do the already-covered test in specDefn, not when we generate + the CallInfo in mkCallUDs. We used to test in the latter place, but + we now iterate the specialiser somewhat, and the Id at the call site + might therefore not have all the RULES that we can see in specDefn + +(SC2) What about two specialisations where the second is an *instance* + of the first? It's a bit arbitrary, but here's what we do: + * If the existing one is user-specified, via a SPECIALISE pragma, we + suppress the further specialisation. + * If the existing one is auto-generated, we generate a second RULE + for the more specialised version. + The latter is important because we don't want the accidental order + of calls to determine what specialisations we generate. + +(SC3) Annoyingly, we /also/ eliminate duplicates in `filterCalls`. + See (MP3) in Note [Specialising polymorphic dictionaries] Note [Auto-specialisation and RULES] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2800,12 +2818,10 @@ non-dictionary bindings too. Note [Specialising polymorphic dictionaries] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Note June 2023: This has proved to be quite a tricky optimisation to get right see (#23469, #23109, #21229, #23445) so it is now guarded by a flag `-fpolymorphic-specialisation`. - Consider class M a where { foo :: a -> Int } @@ -2845,11 +2861,26 @@ Here are the moving parts: function. (MP3) If we have f :: forall m. Monoid m => blah, and two calls - (f @(Endo b) (d :: Monoid (Endo b)) - (f @(Endo (c->c)) (d :: Monoid (Endo (c->c))) + (f @(Endo b) (d1 :: Monoid (Endo b)) + (f @(Endo (c->c)) (d2 :: Monoid (Endo (c->c))) we want to generate a specialisation only for the first. The second is just a substitution instance of the first, with no greater specialisation. - Hence the call to `remove_dups` in `filterCalls`. + Hence the use of `removeDupCalls` in `filterCalls`. + + You might wonder if `d2` might be more specialised than `d1`; but no. + This `removeDupCalls` thing is at the definition site of `f`, and both `d1` + and `d2` are in scope. So `d1` is simply more polymorphic than `d2`, but + is just as specialised. + + This distinction is sadly lost once we build a RULE, so `alreadyCovered` + can't be so clever. E.g if we have an existing RULE + forall @a (d1:Ord Int) (d2: Eq a). f @a @Int d1 d2 = ... + and a putative new rule + forall (d1:Ord Int) (d2: Eq Int). f @Int @Int d1 d2 = ... + we /don't/ want the existing rule to subsume the new one. + + So we sadly put up with having two rather different places where we + eliminate duplicates: `alreadyCovered` and `removeDupCalls`. All this arose in #13873, in the unexpected form that a SPECIALISE pragma made the program slower! The reason was that the specialised @@ -2947,16 +2978,29 @@ data CallInfoSet = CIS Id (Bag CallInfo) -- The list of types and dictionaries is guaranteed to -- match the type of f -- The Bag may contain duplicate calls (i.e. f @T and another f @T) - -- These dups are eliminated by already_covered in specCalls + -- These dups are eliminated by alreadyCovered in specCalls data CallInfo - = CI { ci_key :: [SpecArg] -- All arguments + = CI { ci_key :: [SpecArg] -- Arguments of the call + -- See Note [The (CI-KEY) invariant] + , ci_fvs :: IdSet -- Free Ids of the ci_key call -- /not/ including the main id itself, of course -- NB: excluding tyvars: -- See Note [Specialising polymorphic dictionaries] } +{- Note [The (CI-KEY) invariant] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Invariant (CI-KEY): + In the `ci_key :: [SpecArg]` field of `CallInfo`, + * The list is non-empty + * The least element is always a `SpecDict` + +In this way the RULE has as few args as possible, which broadens its +applicability, since rules only fire when saturated. +-} + type DictExpr = CoreExpr ciSetFilter :: (CallInfo -> Bool) -> CallInfoSet -> CallInfoSet @@ -3045,10 +3089,7 @@ mkCallUDs' env f args ci_key :: [SpecArg] ci_key = dropWhileEndLE (not . isSpecDict) $ zipWith mk_spec_arg args pis - -- Drop trailing args until we get to a SpecDict - -- In this way the RULE has as few args as possible, - -- which broadens its applicability, since rules only - -- fire when saturated + -- Establish (CI-KEY): drop trailing args until we get to a SpecDict mk_spec_arg :: OutExpr -> PiTyBinder -> SpecArg mk_spec_arg arg (Named bndr) @@ -3086,34 +3127,75 @@ site, so we only look through ticks that RULE matching looks through -} wantCallsFor :: SpecEnv -> Id -> Bool -wantCallsFor _env _f = True - -- We could reduce the size of the UsageDetails by being less eager - -- about collecting calls for LocalIds: there is no point for - -- ones that are lambda-bound. We can't decide this by looking at - -- the (absence of an) unfolding, because unfoldings for local - -- functions are discarded by cloneBindSM, so no local binder will - -- have an unfolding at this stage. We'd have to keep a candidate - -- set of let-binders. - -- - -- Not many lambda-bound variables have dictionary arguments, so - -- this would make little difference anyway. - -- - -- For imported Ids we could check for an unfolding, but we have to - -- do so anyway in canSpecImport, and it seems better to have it - -- all in one place. So we simply collect usage info for imported - -- overloaded functions. - -{- Note [Interesting dictionary arguments] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Consider this - \a.\d:Eq a. let f = ... in ...(f d)... -There really is not much point in specialising f wrt the dictionary d, -because the code for the specialised f is not improved at all, because -d is lambda-bound. We simply get junk specialisations. - -What is "interesting"? Just that it has *some* structure. But what about -variables? We look in the variable's /unfolding/. And that means -that we must be careful to ensure that dictionaries have unfoldings, +-- See Note [wantCallsFor] +wantCallsFor _env f + = case idDetails f of + RecSelId {} -> False + DataConWorkId {} -> False + DataConWrapId {} -> False + ClassOpId {} -> False + PrimOpId {} -> False + FCallId {} -> False + TickBoxOpId {} -> False + CoVarId {} -> False + + DFunId {} -> True + VanillaId {} -> True + JoinId {} -> True + WorkerLikeId {} -> True + RepPolyId {} -> True + +{- Note [wantCallsFor] +~~~~~~~~~~~~~~~~~~~~~~ +`wantCallsFor env f` says whether the Specialiser should collect calls for +function `f`; other thing being equal, the fewer calls we collect the better. It +is False for things we can't specialise: + +* ClassOpId: never inline and we don't have a defn to specialise; we specialise + them through fireRewriteRules. +* PrimOpId: are never overloaded +* Data constructors: we never specialise them + +We could reduce the size of the UsageDetails by being less eager about +collecting calls for some LocalIds: there is no point for ones that are +lambda-bound. We can't decide this by looking at the (absence of an) unfolding, +because unfoldings for local functions are discarded by cloneBindSM, so no local +binder will have an unfolding at this stage. We'd have to keep a candidate set +of let-binders. + +Not many lambda-bound variables have dictionary arguments, so this would make +little difference anyway. + +For imported Ids we could check for an unfolding, but we have to do so anyway in +canSpecImport, and it seems better to have it all in one place. So we simply +collect usage info for imported overloaded functions. + +Note [Interesting dictionary arguments] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In `mkCallUDs` we only use `SpecDict` for dictionaries of which +`interestingDict` holds. Otherwise we use `UnspecArg`. Two reasons: + +* Consider this + \a.\d:Eq a. let f = ... in ...(f d)... + There really is not much point in specialising f wrt the dictionary d, + because the code for the specialised f is not improved at all, because + d is lambda-bound. We simply get junk specialisations. + +* Consider this (#25703): + f :: (Eq a, Show b) => a -> b -> INt + goo :: forall x. (Eq x) => x -> blah + goo @x (d:Eq x) (arg:x) = ...(f @x @Int d $fShowInt)... + If we built a `ci_key` with a (SpecDict d) for `d`, we would end up + discarding the call at the `\d`. But if we use `UnspecArg` for that + uninteresting `d`, we'll get a `ci_key` of + f @x @Int UnspecArg (SpecDict $fShowInt) + and /that/ can float out to f's definition and specialise nicely. + Hooray. + +What is "interesting"? (See `interestingDict`.) Just that it has *some* +structure. But what about variables? We look in the variable's /unfolding/. +And that means that we must be careful to ensure that dictionaries /have/ +unfoldings, * cloneBndrSM discards non-Stable unfoldings * specBind updates the unfolding after specialisation @@ -3159,7 +3241,7 @@ Now `f` turns into: meth @a dc .... When we specialise `f`, at a=Int say, that superclass selection can -nfire (via rewiteClassOps), but that info (that 'dc' is now a +fire (via rewiteClassOps), but that info (that 'dc' is now a particular dictionary `C`, of type `C Int`) must be available to the call `meth @a dc`, so that we can fire the `meth` class-op, and thence specialise `wombat`. @@ -3286,7 +3368,11 @@ dumpUDs :: [CoreBndr] -> UsageDetails -> (UsageDetails, OrdList DictBind) -- Used at a lambda or case binder; just dump anything mentioning the binder dumpUDs bndrs uds@(MkUD { ud_binds = orig_dbs, ud_calls = orig_calls }) | null bndrs = (uds, nilOL) -- Common in case alternatives - | otherwise = -- pprTrace "dumpUDs" (ppr bndrs $$ ppr free_uds $$ ppr dump_dbs) $ + | otherwise = -- pprTrace "dumpUDs" (vcat + -- [ text "bndrs" <+> ppr bndrs + -- , text "uds" <+> ppr uds + -- , text "free_uds" <+> ppr free_uds + -- , text "dump-dbs" <+> ppr dump_dbs ]) $ (free_uds, dump_dbs) where free_uds = uds { ud_binds = free_dbs, ud_calls = free_calls } @@ -3325,20 +3411,17 @@ callsForMe fn uds@MkUD { ud_binds = orig_dbs, ud_calls = orig_calls } calls_for_me = case lookupDVarEnv orig_calls fn of Nothing -> [] Just cis -> filterCalls cis orig_dbs - -- filterCalls: drop calls that (directly or indirectly) - -- refer to fn. See Note [Avoiding loops (DFuns)] ---------------------- filterCalls :: CallInfoSet -> FloatedDictBinds -> [CallInfo] --- Remove dominated calls (Note [Specialising polymorphic dictionaries]) --- and loopy DFuns (Note [Avoiding loops (DFuns)]) +-- Remove +-- (a) dominated calls: (MP3) in Note [Specialising polymorphic dictionaries] +-- (b) loopy DFuns: Note [Avoiding loops (DFuns)] filterCalls (CIS fn call_bag) (FDB { fdb_binds = dbs }) - | isDFunId fn -- Note [Avoiding loops (DFuns)] applies only to DFuns - = filter ok_call de_dupd_calls - | otherwise -- Do not apply it to non-DFuns - = de_dupd_calls -- See Note [Avoiding loops (non-DFuns)] + | isDFunId fn = filter ok_call de_dupd_calls -- Deals with (b) + | otherwise = de_dupd_calls where - de_dupd_calls = remove_dups call_bag + de_dupd_calls = removeDupCalls call_bag -- Deals with (a) dump_set = foldl' go (unitVarSet fn) dbs -- This dump-set could also be computed by splitDictBinds @@ -3352,10 +3435,10 @@ filterCalls (CIS fn call_bag) (FDB { fdb_binds = dbs }) ok_call (CI { ci_fvs = fvs }) = fvs `disjointVarSet` dump_set -remove_dups :: Bag CallInfo -> [CallInfo] +removeDupCalls :: Bag CallInfo -> [CallInfo] -- Calls involving more generic instances beat more specific ones. -- See (MP3) in Note [Specialising polymorphic dictionaries] -remove_dups calls = foldr add [] calls +removeDupCalls calls = foldr add [] calls where add :: CallInfo -> [CallInfo] -> [CallInfo] add ci [] = [ci] @@ -3364,12 +3447,20 @@ remove_dups calls = foldr add [] calls | otherwise = ci2 : add ci1 cis beats_or_same :: CallInfo -> CallInfo -> Bool +-- (beats_or_same ci1 ci2) is True if specialising on ci1 subsumes ci2 +-- That is: ci1's types are less specialised than ci2 +-- ci1 specialises on the same dict args as ci2 beats_or_same (CI { ci_key = args1 }) (CI { ci_key = args2 }) = go args1 args2 where - go [] _ = True + go [] [] = True go (arg1:args1) (arg2:args2) = go_arg arg1 arg2 && go args1 args2 - go (_:_) [] = False + + -- If one or the other runs dry, the other must still have a SpecDict + -- because of the (CI-KEY) invariant. So neither subsumes the other; + -- one is more specialised (faster code) but the other is more generally + -- applicable. + go _ _ = False go_arg (SpecType ty1) (SpecType ty2) = isJust (tcMatchTy ty1 ty2) go_arg UnspecType UnspecType = True ===================================== compiler/GHC/Core/Rules.hs ===================================== @@ -9,7 +9,7 @@ -- The 'CoreRule' datatype itself is declared elsewhere. module GHC.Core.Rules ( -- ** Looking up rules - lookupRule, matchExprs, + lookupRule, matchExprs, ruleLhsIsMoreSpecific, -- ** RuleBase, RuleEnv RuleBase, RuleEnv(..), mkRuleEnv, emptyRuleEnv, @@ -587,8 +587,8 @@ findBest :: InScopeSet -> (Id, [CoreExpr]) findBest _ _ (rule,ans) [] = (rule,ans) findBest in_scope target (rule1,ans1) ((rule2,ans2):prs) - | isMoreSpecific in_scope rule1 rule2 = findBest in_scope target (rule1,ans1) prs - | isMoreSpecific in_scope rule2 rule1 = findBest in_scope target (rule2,ans2) prs + | ruleIsMoreSpecific in_scope rule1 rule2 = findBest in_scope target (rule1,ans1) prs + | ruleIsMoreSpecific in_scope rule2 rule1 = findBest in_scope target (rule2,ans2) prs | debugIsOn = let pp_rule rule = ifPprDebug (ppr rule) (doubleQuotes (ftext (ruleName rule))) @@ -603,15 +603,25 @@ findBest in_scope target (rule1,ans1) ((rule2,ans2):prs) where (fn,args) = target -isMoreSpecific :: InScopeSet -> CoreRule -> CoreRule -> Bool --- The call (rule1 `isMoreSpecific` rule2) +ruleIsMoreSpecific :: InScopeSet -> CoreRule -> CoreRule -> Bool +-- The call (rule1 `ruleIsMoreSpecific` rule2) -- sees if rule2 can be instantiated to look like rule1 --- See Note [isMoreSpecific] -isMoreSpecific _ (BuiltinRule {}) _ = False -isMoreSpecific _ (Rule {}) (BuiltinRule {}) = True -isMoreSpecific in_scope (Rule { ru_bndrs = bndrs1, ru_args = args1 }) - (Rule { ru_bndrs = bndrs2, ru_args = args2 }) - = isJust (matchExprs in_scope_env bndrs2 args2 args1) +-- See Note [ruleIsMoreSpecific] +ruleIsMoreSpecific in_scope rule1 rule2 + = case rule1 of + BuiltinRule {} -> False + Rule { ru_bndrs = bndrs1, ru_args = args1 } + -> ruleLhsIsMoreSpecific in_scope bndrs1 args1 rule2 + +ruleLhsIsMoreSpecific :: InScopeSet + -> [Var] -> [CoreExpr] -- LHS of a possible new rule + -> CoreRule -- An existing rule + -> Bool -- New one is more specific +ruleLhsIsMoreSpecific in_scope bndrs1 args1 rule2 + = case rule2 of + BuiltinRule {} -> True + Rule { ru_bndrs = bndrs2, ru_args = args2 } + -> isJust (matchExprs in_scope_env bndrs2 args2 args1) where full_in_scope = in_scope `extendInScopeSetList` bndrs1 in_scope_env = ISE full_in_scope noUnfoldingFun @@ -620,9 +630,9 @@ isMoreSpecific in_scope (Rule { ru_bndrs = bndrs1, ru_args = args1 }) noBlackList :: Activation -> Bool noBlackList _ = False -- Nothing is black listed -{- Note [isMoreSpecific] +{- Note [ruleIsMoreSpecific] ~~~~~~~~~~~~~~~~~~~~~~~~ -The call (rule1 `isMoreSpecific` rule2) +The call (rule1 `ruleIsMoreSpecific` rule2) sees if rule2 can be instantiated to look like rule1. Wrinkle: @@ -825,7 +835,7 @@ bound on the LHS: The rule looks like forall (a::*) (d::Eq Char) (x :: Foo a Char). - f (Foo a Char) d x = True + f @(Foo a Char) d x = True Matching the rule won't bind 'a', and legitimately so. We fudge by pretending that 'a' is bound to (Any :: *). ===================================== compiler/GHC/Core/Unify.hs ===================================== @@ -331,35 +331,57 @@ Wrinkles `DontBindMe`, the unifier must return `SurelyApart`, not `MaybeApart`. See `go_fam` in `uVarOrFam` -(ATF6) You might think that when /matching/ the um_fam_env will always be empty, - because type-class-instance and type-family-instance heads can't include type - families. E.g. instance C (F a) where ... -- Illegal - - But you'd be wrong: when "improving" type family constraint we may have a - type family on the LHS of a match. Consider +(ATF6) When /matching/ can we ever have a type-family application on the LHS, in + the template? You might think not, because type-class-instance and + type-family-instance heads can't include type families. E.g. + instance C (F a) where ... -- Illegal + + But you'd be wrong: even when matching, we can see type families in the LHS template: + * In `checkValidClass`, in `check_dm` we check that the default method has the + right type, using matching, both ways. And that type may have type-family + applications in it. Example in test CoOpt_Singletons. + + * In the specialiser: see the call to `tcMatchTy` in + `GHC.Core.Opt.Specialise.beats_or_same` + + * With -fpolymorphic-specialsation, we might get a specialiation rule like + RULE forall a (d :: Eq (Maybe (F a))) . + f @(Maybe (F a)) d = ... + See #25965. + + * A user-written RULE could conceivably have a type-family application + in the template. It might not be a good rule, but I don't think we currently + check for this. + + In all these cases we are only interested in finding a substitution /for + type variables/ that makes the match work. So we simply want to recurse into + the arguments of the type family. E.g. + Template: forall a. Maybe (F a) + Target: Mabybe (F Int) + We want to succeed with substitution [a :-> Int]. See (ATF9). + + Conclusion: where we enter via `tcMatchTy`, `tcMatchTys`, `tc_match_tys`, + etc, we always end up in `tc_match_tys_x`. There we invoke the unifier + but we do not distinguish between `SurelyApart` and `MaybeApart`. So in + these cases we can set `um_bind_fam_fun` to `neverBindFam`. + +(ATF7) There is one other, very special case of matching where we /do/ want to + bind type families in `um_fam_env`, namely in GHC.Tc.Solver.Equality, the call + to `tcUnifyTyForInjectivity False` in `improve_injective_wanted_top`. + Consider + of a match. Consider type family G6 a = r | r -> a type instance G6 [a] = [G a] type instance G6 Bool = Int - and the Wanted constraint [W] G6 alpha ~ [Int]. We /match/ each type instance - RHS against [Int]! So we try - [G a] ~ [Int] + and suppose we haev a Wanted constraint + [W] G6 alpha ~ [Int] +. According to Section 5.2 of "Injective type families for Haskell", we /match/ + the RHS each type instance [Int]. So we try + Template: [G a] Target: [Int] and we want to succeed with MaybeApart, so that we can generate the improvement - constraint [W] alpha ~ [beta] where beta is fresh. - See Section 5.2 of "Injective type families for Haskell". - - A second place that we match with type-fams on the LHS is in `checkValidClass`. - In `check_dm` we check that the default method has the right type, using matching, - both ways. And that type may have type-family applications in it. Example in - test CoOpt_Singletons. - -(ATF7) You might think that (ATF6) is a very special case, and in /other/ uses of - matching, where we enter via `tc_match_tys_x` we will never see a type-family - in the template. But actually we do see that case in the specialiser: see - the call to `tcMatchTy` in `GHC.Core.Opt.Specialise.beats_or_same` - - Also: a user-written RULE could conceivably have a type-family application - in the template. It might not be a good rule, but I don't think we currently - check for this. + constraint + [W] alpha ~ [beta] + where beta is fresh. We do this by binding [G a :-> Int] (ATF8) The treatment of type families is governed by um_bind_fam_fun :: BindFamFun @@ -399,6 +421,8 @@ Wrinkles Key point: when decomposing (F tys1 ~ F tys2), we should /also/ extend the type-family substitution. + (ATF11-1) All this cleverness only matters when unifying, not when matching + (ATF12) There is a horrid exception for the injectivity check. See (UR1) in in Note [Specification of unification]. @@ -595,7 +619,7 @@ tc_match_tys_x :: HasDebugCallStack -> [Type] -> Maybe Subst tc_match_tys_x bind_tv match_kis (Subst in_scope id_env tv_env cv_env) tys1 tys2 - = case tc_unify_tys alwaysBindFam -- (ATF7) in Note [Apartness and type families] + = case tc_unify_tys neverBindFam -- (ATF7) in Note [Apartness and type families] bind_tv False -- Matching, not unifying False -- Not an injectivity check @@ -1857,6 +1881,7 @@ uVarOrFam env ty1 ty2 kco = go_fam_fam tc1 tys1 tys2 kco -- Now check if we can bind the (F tys) to the RHS + -- This can happen even when matching: see (ATF7) | BindMe <- um_bind_fam_fun env tc1 tys1 rhs = -- ToDo: do we need an occurs check here? do { extendFamEnv tc1 tys1 rhs @@ -1881,11 +1906,6 @@ uVarOrFam env ty1 ty2 kco -- go_fam_fam: LHS and RHS are both saturated type-family applications, -- for the same type-family F go_fam_fam tc tys1 tys2 kco - | tcEqTyConAppArgs tys1 tys2 - -- Detect (F tys ~ F tys); otherwise we'd build an infinite substitution - = return () - - | otherwise -- Decompose (F tys1 ~ F tys2): (ATF9) -- Use injectivity information of F: (ATF10) -- But first bind the type-fam if poss: (ATF11) @@ -1902,13 +1922,19 @@ uVarOrFam env ty1 ty2 kco (inj_tys1, noninj_tys1) = partitionByList inj tys1 (inj_tys2, noninj_tys2) = partitionByList inj tys2 - bind_fam_if_poss | BindMe <- um_bind_fam_fun env tc tys1 rhs1 - = extendFamEnv tc tys1 rhs1 - | um_unif env - , BindMe <- um_bind_fam_fun env tc tys2 rhs2 - = extendFamEnv tc tys2 rhs2 - | otherwise - = return () + bind_fam_if_poss + | not (um_unif env) -- Not when matching (ATF11-1) + = return () + | tcEqTyConAppArgs tys1 tys2 -- Detect (F tys ~ F tys); + = return () -- otherwise we'd build an infinite substitution + | BindMe <- um_bind_fam_fun env tc tys1 rhs1 + = extendFamEnv tc tys1 rhs1 + | um_unif env + , BindMe <- um_bind_fam_fun env tc tys2 rhs2 + = extendFamEnv tc tys2 rhs2 + | otherwise + = return () + rhs1 = mkTyConApp tc tys2 `mkCastTy` mkSymCo kco rhs2 = mkTyConApp tc tys1 `mkCastTy` kco @@ -1993,7 +2019,7 @@ data UMState = UMState -- in um_foralls; i.e. variables bound by foralls inside the types being unified -- When /matching/ um_fam_env is usually empty; but not quite always. - -- See (ATF6) and (ATF7) of Note [Apartness and type families] + -- See (ATF7) of Note [Apartness and type families] newtype UM a = UM' { unUM :: UMState -> UnifyResultM (UMState, a) } ===================================== compiler/GHC/Tc/Solver/Equality.hs ===================================== @@ -3017,6 +3017,7 @@ improve_wanted_top_fun_eqs fam_tc lhs_tys rhs_ty improve_injective_wanted_top :: FamInstEnvs -> [Bool] -> TyCon -> [TcType] -> Xi -> TcS [TypeEqn] -- Interact with top-level instance declarations +-- See Section 5.2 in the Injective Type Families paper improve_injective_wanted_top fam_envs inj_args fam_tc lhs_tys rhs_ty = concatMapM do_one branches where @@ -3035,6 +3036,7 @@ improve_injective_wanted_top fam_envs inj_args fam_tc lhs_tys rhs_ty do_one branch@(CoAxBranch { cab_tvs = branch_tvs, cab_lhs = branch_lhs_tys, cab_rhs = branch_rhs }) | let in_scope1 = in_scope `extendInScopeSetList` branch_tvs , Just subst <- tcUnifyTyForInjectivity False in_scope1 branch_rhs rhs_ty + -- False: matching, not unifying = do { let inSubst tv = tv `elemVarEnv` getTvSubstEnv subst unsubstTvs = filterOut inSubst branch_tvs -- The order of unsubstTvs is important; it must be ===================================== compiler/GHC/Types/Basic.hs ===================================== @@ -85,7 +85,7 @@ module GHC.Types.Basic ( CompilerPhase(..), PhaseNum, beginPhase, nextPhase, laterPhase, Activation(..), isActive, competesWith, - isNeverActive, isAlwaysActive, activeInFinalPhase, + isNeverActive, isAlwaysActive, activeInFinalPhase, activeInInitialPhase, activateAfterInitial, activateDuringFinal, activeAfter, RuleMatchInfo(..), isConLike, isFunLike, ===================================== testsuite/tests/simplCore/should_compile/T25703.hs ===================================== @@ -0,0 +1,7 @@ +module T25703 where + +f :: (Eq a, Show b) => a -> b -> Int +f x y = f x y + +goo :: forall x. (Eq x) => x -> Int +goo arg = f arg (3::Int) ===================================== testsuite/tests/simplCore/should_compile/T25703.stderr ===================================== @@ -0,0 +1,2 @@ +Rule fired: SPEC f @_ @Int (T25703) +Rule fired: SPEC f @_ @Int (T25703) ===================================== testsuite/tests/simplCore/should_compile/T25703a.hs ===================================== @@ -0,0 +1,69 @@ +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE GADTs #-} + +{-# OPTIONS_GHC -O2 -fspecialise-aggressively #-} + +-- This pragma is just here to pretend that the function body of 'foo' is huge +-- and should never be inlined. +{-# OPTIONS_GHC -funfolding-use-threshold=-200 #-} + +module T25703a where + +import Data.Kind +import Data.Type.Equality +import Data.Proxy +import GHC.TypeNats + +-- Pretend this is some big dictionary that absolutely must get +-- specialised away for performance reasons. +type C :: Nat -> Constraint +class C i where + meth :: Proxy i -> Double +instance C 0 where + meth _ = 0.1 +instance C 1 where + meth _ = 1.1 +instance C 2 where + meth _ = 2.1 + +{-# INLINEABLE foo #-} +foo :: forall a (n :: Nat) (m :: Nat) + . ( Eq a, C n, C m ) + => a -> ( Proxy n, Proxy m ) -> Int -> Double +-- Pretend this is a big complicated function, too big to inline, +-- for which we absolutely must specialise away the 'C n', 'C m' +-- dictionaries for performance reasons. +foo a b c + = if a == a + then meth @n Proxy + fromIntegral c + else 2 * meth @m Proxy + +-- Runtime dispatch to a specialisation of 'foo' +foo_spec :: forall a (n :: Nat) (m :: Nat) + . ( Eq a, KnownNat n, KnownNat m ) + => a -> ( Proxy n, Proxy m ) -> Int -> Double +foo_spec a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @0 Proxy Proxy + = foo @a @0 @0 a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @1 Proxy Proxy + = foo @a @0 @1 a b c + | Just Refl <- sameNat @n @1 Proxy Proxy + , Just Refl <- sameNat @m @1 Proxy Proxy + = foo @a @1 @1 a b c + | Just Refl <- sameNat @n @0 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @0 @2 a b c + | Just Refl <- sameNat @n @1 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @1 @2 a b c + | Just Refl <- sameNat @n @2 Proxy Proxy + , Just Refl <- sameNat @m @2 Proxy Proxy + = foo @a @2 @2 a b c + | otherwise + = error $ unlines + [ "f: no specialisation" + , "n: " ++ show (natVal @n Proxy) + , "m: " ++ show (natVal @m Proxy) + ] ===================================== testsuite/tests/simplCore/should_compile/T25703a.stderr ===================================== @@ -0,0 +1,6 @@ +Rule fired: SPEC foo @_ @2 @2 (T25703a) +Rule fired: SPEC foo @_ @1 @2 (T25703a) +Rule fired: SPEC foo @_ @0 @2 (T25703a) +Rule fired: SPEC foo @_ @1 @1 (T25703a) +Rule fired: SPEC foo @_ @0 @1 (T25703a) +Rule fired: SPEC foo @_ @0 @0 (T25703a) ===================================== testsuite/tests/simplCore/should_compile/T25965.hs ===================================== @@ -0,0 +1,18 @@ +{-# LANGUAGE TypeFamilies #-} +{-# OPTIONS_GHC -O -fpolymorphic-specialisation #-} + +module Foo where + +type family F a + +data T a = T1 + +instance Eq (T a) where { (==) x y = False } + +foo :: Eq a => a -> Bool +foo x | x==x = True + | otherwise = foo x + +bar :: forall b. b -> T (F b) -> Bool +bar y x = foo x + ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -535,3 +535,6 @@ test('T25197', [req_th, extra_files(["T25197_TH.hs"]), only_ways(['optasm'])], m test('T25389', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dno-typeable-binds']) test('T24359a', normal, compile, ['-O -ddump-rules']) test('T25713', [grep_errmsg('W:::')], compile, ['-O -ddump-simpl']) +test('T25965', normal, compile, ['-O']) +test('T25703', [grep_errmsg(r'SPEC')], compile, ['-O -fpolymorphic-specialisation -ddump-rule-firings']) +test('T25703a', [grep_errmsg(r'SPEC')], compile, ['-O -fpolymorphic-specialisation -ddump-rule-firings']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/241c93c076e2ac2d2a1e2c1377c1996… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/241c93c076e2ac2d2a1e2c1377c1996… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 2 commits: Refactor Handling of Multiple Default Declarations
by Marge Bot (＠marge-bot) 16 Apr '25

16 Apr '25

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 566e79de by Patrick at 2025-04-16T19:50:19-04:00 Refactor Handling of Multiple Default Declarations Fixes: #25912, #25914, #25934 Previously, GHC discarded all loaded defaults (tcg_default) when local defaults were encountered during typechecking. According to the exportable-named-default proposal (sections 2.4.2 and 2.4.3), local defaults should be merged into tcg_default, retaining any defaults already present while overriding where necessary. Key Changes: * Introduce DefaultProvenance to track the origin of default declarations (local, imported, or built-in), replacing the original cd_module in ClassDefaults with cd_provenance :: DefaultProvenance. * Rename tcDefaults to tcDefaultDecls, limiting its responsibility to only converting renamed class defaults into ClassDefaults. * Add extendDefaultEnvWithLocalDefaults to merge local defaults into the environment, with proper duplication checks: - Duplicate local defaults for a class trigger an error. - Local defaults override imported or built-in defaults. * Update and add related notes: Note [Builtin class defaults], Note [DefaultProvenance]. * Add regression tests: T25912, T25914, T25934. Thanks sam and simon for the help on this patch. Co-authored-by: sheaf <sam.derbyshire(a)gmail.com> - - - - - 5e7df774 by Teo Camarasu at 2025-04-16T19:50:20-04:00 template-haskell: Remove `addrToByteArrayName` and `addrToByteArray` These were part of the implementation of the `Lift ByteArray` instance and were errornously exported because this module lacked an explicit export list. They have no usages on Hackage. Resolves #24782 - - - - - 20 changed files: - compiler/GHC/IfaceToCore.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Default.hs - compiler/GHC/Tc/Gen/Export.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Types/DefaultEnv.hs - libraries/template-haskell/Language/Haskell/TH/Syntax.hs - libraries/template-haskell/changelog.md - + testsuite/tests/default/T25912.hs - + testsuite/tests/default/T25912.stdout - + testsuite/tests/default/T25912_helper.hs - + testsuite/tests/default/T25914.hs - + testsuite/tests/default/T25934.hs - testsuite/tests/default/all.T - testsuite/tests/default/default-fail03.stderr - testsuite/tests/interface-stability/template-haskell-exports.stdout - testsuite/tests/linters/notes.stdout - testsuite/tests/module/mod58.stderr Changes: ===================================== compiler/GHC/IfaceToCore.hs ===================================== @@ -118,7 +118,7 @@ import GHC.Types.Var.Set import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Env -import GHC.Types.DefaultEnv ( ClassDefaults(..), DefaultEnv, mkDefaultEnv ) +import GHC.Types.DefaultEnv ( ClassDefaults(..), DefaultEnv, mkDefaultEnv, DefaultProvenance(..) ) import GHC.Types.Id import GHC.Types.Id.Make import GHC.Types.Id.Info @@ -1333,7 +1333,7 @@ tcIfaceDefault this_mod IfaceDefault { ifDefaultCls = cls_name ; let warn = fmap fromIfaceWarningTxt iface_warn ; return ClassDefaults { cd_class = cls , cd_types = tys' - , cd_module = Just this_mod + , cd_provenance = DP_Imported this_mod , cd_warn = warn } } where tyThingConClass :: TyThing -> Class ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -85,7 +85,7 @@ import GHC.Tc.Types.Rank (Rank(..)) import GHC.Tc.Types.TH import GHC.Tc.Utils.TcType -import GHC.Types.DefaultEnv (ClassDefaults(ClassDefaults, cd_types, cd_module)) +import GHC.Types.DefaultEnv (ClassDefaults(ClassDefaults, cd_types, cd_provenance), DefaultProvenance (..)) import GHC.Types.Error import GHC.Types.Error.Codes import GHC.Types.Hint @@ -582,11 +582,19 @@ instance Diagnostic TcRnMessage where TcRnMultipleDefaultDeclarations cls dup_things -> mkSimpleDecorated $ hang (text "Multiple default declarations for class" <+> quotes (ppr cls)) - 2 (vcat (map pp dup_things)) + 2 (pp dup_things) where - pp :: LDefaultDecl GhcRn -> SDoc - pp (L locn DefaultDecl {}) - = text "here was another default declaration" <+> ppr (locA locn) + pp :: ClassDefaults -> SDoc + pp (ClassDefaults { cd_provenance = prov }) + = case prov of + DP_Local { defaultDeclLoc = loc, defaultDeclH98 = isH98 } + -> let + what = + if isH98 + then text "default declaration" + else text "named default declaration" + in text "conflicting" <+> what <+> text "at:" <+> ppr loc + _ -> empty -- doesn't happen, as local defaults override imported and built-in defaults TcRnBadDefaultType ty deflt_clss -> mkSimpleDecorated $ hang (text "The default type" <+> quotes (ppr ty) <+> text "is not an instance of") @@ -7139,7 +7147,7 @@ pprPatersonCondFailure (PCF_TyFam tc) InTyFamEquation _lhs rhs = -------------------------------------------------------------------------------- defaultTypesAndImport :: ClassDefaults -> SDoc -defaultTypesAndImport ClassDefaults{cd_types, cd_module = Just cdm} = +defaultTypesAndImport ClassDefaults{cd_types, cd_provenance = DP_Imported cdm} = hang (parens $ pprWithCommas ppr cd_types) 2 (text "imported from" <+> ppr cdm) defaultTypesAndImport ClassDefaults{cd_types} = parens (pprWithCommas ppr cd_types) ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -1504,7 +1504,7 @@ data TcRnMessage where Text cases: module/mod58 -} - TcRnMultipleDefaultDeclarations :: Class -> [LDefaultDecl GhcRn] -> TcRnMessage + TcRnMultipleDefaultDeclarations :: Class -> ClassDefaults -> TcRnMessage {-| TcRnWarnClashingDefaultImports is a warning that occurs when a module imports more than one default declaration for the same class, and they are not all ===================================== compiler/GHC/Tc/Gen/Default.hs ===================================== @@ -5,9 +5,10 @@ -} {-# LANGUAGE MultiWayIf #-} {-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE LambdaCase #-} -- | Typechecking @default@ declarations -module GHC.Tc.Gen.Default ( tcDefaults ) where +module GHC.Tc.Gen.Default ( tcDefaultDecls, extendDefaultEnvWithLocalDefaults ) where import GHC.Prelude import GHC.Hs @@ -16,7 +17,7 @@ import GHC.Builtin.Names import GHC.Core.Class import GHC.Core.Predicate ( Pred (..), classifyPredType ) -import GHC.Data.Maybe ( firstJusts ) +import GHC.Data.Maybe ( firstJusts, maybeToList ) import GHC.Tc.Errors.Types import GHC.Tc.Gen.HsType @@ -30,20 +31,17 @@ import GHC.Tc.Utils.TcMType ( newWanted ) import GHC.Tc.Utils.TcType import GHC.Types.Basic ( TypeOrKind(..) ) -import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults (..), defaultEnv ) +import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults (..), lookupDefaultEnv, insertDefaultEnv, DefaultProvenance (..) ) import GHC.Types.SrcLoc -import GHC.Unit.Types (Module, ghcInternalUnit, moduleUnit) +import GHC.Unit.Types (ghcInternalUnit, moduleUnit) -import GHC.Utils.Misc (fstOf3, sndOf3) import GHC.Utils.Outputable import qualified GHC.LanguageExtensions as LangExt -import Data.Function (on) -import Data.List.NonEmpty ( NonEmpty (..), groupBy ) +import Data.List.NonEmpty ( NonEmpty (..) ) import qualified Data.List.NonEmpty as NE -import Data.Maybe (fromMaybe) import Data.Traversable ( for ) {- Note [Named default declarations] @@ -86,7 +84,7 @@ The moving parts are as follows: * The `DefaultEnv` of all defaults in scope in a module is kept in the `tcg_default` field of `TcGblEnv`. -* This field is populated by `GHC.Tc.Gen.Default.tcDefaults` which typechecks +* This field is populated by `GHC.Tc.Gen.Default.tcDefaultDecls` which typechecks any local or imported `default` declarations. * Only a single default declaration can be in effect in any single module for @@ -103,7 +101,7 @@ The moving parts are as follows: in effect be `default Num (Integer, Double)` as specified by Haskell Language Report. - See Note [Default class defaults] in GHC.Tc.Utils.Env + See Note [Builtin class defaults] in GHC.Tc.Utils.Env * Beside the defaults, the `ExtendedDefaultRules` and `OverloadedStrings` extensions also affect the traditional `default` declarations that don't name @@ -120,61 +118,54 @@ The moving parts are as follows: tracked separately from `ImportAvails`, and returned separately from them by `GHC.Rename.Names.rnImports`. -* Class defaults are exported explicitly, as the example above shows. A module's - exported defaults are tracked in `tcg_default_exports`, which are then - transferred to `mg_defaults`, `md_defaults`, and `mi_defaults_`. +* Class defaults are exported explicitly. + For example, + module M( ..., default C, ... ) + exports the defaults for class C. + + A module's exported defaults are computed by exports_from_avail, + tracked in tcg_default_exports, which are then transferred to mg_defaults, + md_defaults, and mi_defaults_. + + Only defaults explicitly exported are actually exported. + (i.e. No defaults are exported in a module header like: + module M where ...) + See Note [Default exports] in GHC.Tc.Gen.Export * Since the class defaults merely help the solver infer the correct types, they leave no trace in Haskell Core. -} --- See Note [Named default declarations] -tcDefaults :: [LDefaultDecl GhcRn] - -> TcM DefaultEnv -- Defaulting types to heave - -- into Tc monad for later use - -- in Disambig. - -tcDefaults [] - = getDeclaredDefaultTys -- No default declaration, so get the - -- default types from the envt; - -- i.e. use the current ones - -- (the caller will put them back there) - -- It's important not to return defaultDefaultTys here (which - -- we used to do) because in a TH program, tcDefaults [] is called - -- repeatedly, once for each group of declarations between top-level - -- splices. We don't want to carefully set the default types in - -- one group, only for the next group to ignore them and install - -- defaultDefaultTys - -tcDefaults decls - = do { tcg_env <- getGblEnv - ; let - here = tcg_mod tcg_env - is_internal_unit = moduleUnit here == ghcInternalUnit - ; case (is_internal_unit, decls) of - -- Some internal GHC modules contain @default ()@ to declare that no defaults can take place - -- in the module. - -- We shortcut the treatment of such a default declaration with no class nor types: we won't - -- try to point 'cd_class' to 'Num' since it may not even exist yet. - { (True, [L _ (DefaultDecl _ Nothing [])]) - -> return $ defaultEnv [] - -- Otherwise we take apart the declaration into the class constructor and its default types. - ; _ -> - do { h2010_dflt_clss <- getH2010DefaultClasses - ; decls' <- mapMaybeM (declarationParts h2010_dflt_clss) decls - ; let - -- Find duplicate default declarations - decl_tag (mb_cls, _, _) = - case mb_cls of - Nothing -> Nothing - Just cls -> if cls `elem` h2010_dflt_clss - then Nothing - else Just cls - decl_groups = groupBy ((==) `on` decl_tag) decls' - ; decls_without_dups <- mapM (reportDuplicates here h2010_dflt_clss) decl_groups - ; return $ defaultEnv (concat decls_without_dups) - } } } +-- | Typecheck a collection of default declarations. These can be either: +-- +-- - Haskell 98 default declarations, of the form @default (Float, Double)@ +-- - Named default declarations, of the form @default Cls(Int, Char)@. +-- See Note [Named default declarations] +tcDefaultDecls :: [LDefaultDecl GhcRn] -> TcM [LocatedA ClassDefaults] +tcDefaultDecls decls = + do + tcg_env <- getGblEnv + let here = tcg_mod tcg_env + is_internal_unit = moduleUnit here == ghcInternalUnit + case (is_internal_unit, decls) of + -- No default declarations + (_, []) -> return [] + -- As per Remark [default () in ghc-internal] in Note [Builtin class defaults], + -- some modules in ghc-internal include an empty `default ()` declaration, in order + -- to disable built-in defaults. This is no longer necessary (see `GHC.Tc.Utils.Env.tcGetDefaultTys`), + -- but we must still make sure not to error if we fail to look up e.g. the 'Num' + -- typeclass when typechecking such a default declaration. To do this, we wrap + -- calls of 'tcLookupClass' in 'tryTc'. + (True, [L _ (DefaultDecl _ Nothing [])]) -> do + h2010_dflt_clss <- foldMapM (fmap maybeToList . fmap fst . tryTc . tcLookupClass) =<< getH2010DefaultNames + case NE.nonEmpty h2010_dflt_clss of + Nothing -> return [] + Just h2010_dflt_clss' -> toClassDefaults h2010_dflt_clss' decls + -- Otherwise we take apart the declaration into the class constructor and its default types. + _ -> do + h2010_dflt_clss <- getH2010DefaultClasses + toClassDefaults h2010_dflt_clss decls where getH2010DefaultClasses :: TcM (NonEmpty Class) -- All the classes subject to defaulting with a Haskell 2010 default @@ -186,18 +177,18 @@ tcDefaults decls -- No extensions: Num -- OverloadedStrings: add IsString -- ExtendedDefaults: add Show, Eq, Ord, Foldable, Traversable - getH2010DefaultClasses - = do { num_cls <- tcLookupClass numClassName - ; ovl_str <- xoptM LangExt.OverloadedStrings + getH2010DefaultClasses = mapM tcLookupClass =<< getH2010DefaultNames + getH2010DefaultNames + = do { ovl_str <- xoptM LangExt.OverloadedStrings ; ext_deflt <- xoptM LangExt.ExtendedDefaultRules - ; deflt_str <- if ovl_str - then mapM tcLookupClass [isStringClassName] - else return [] - ; deflt_interactive <- if ext_deflt - then mapM tcLookupClass interactiveClassNames - else return [] - ; let extra_clss = deflt_str ++ deflt_interactive - ; return $ num_cls :| extra_clss + ; let deflt_str = if ovl_str + then [isStringClassName] + else [] + ; let deflt_interactive = if ext_deflt + then interactiveClassNames + else [] + ; let extra_clss_names = deflt_str ++ deflt_interactive + ; return $ numClassName :| extra_clss_names } declarationParts :: NonEmpty Class -> LDefaultDecl GhcRn -> TcM (Maybe (Maybe Class, LDefaultDecl GhcRn, [Type])) declarationParts h2010_dflt_clss decl@(L locn (DefaultDecl _ mb_cls_name dflt_hs_tys)) @@ -220,20 +211,49 @@ tcDefaults decls ; return (Just cls, decl, tau_tys) } } - reportDuplicates :: Module -> NonEmpty Class -> NonEmpty (Maybe Class, LDefaultDecl GhcRn, [Type]) -> TcM [ClassDefaults] - reportDuplicates here h2010_dflt_clss ((mb_cls, _, tys) :| []) - = pure [ ClassDefaults{cd_class = c, cd_types = tys, cd_module = Just here, cd_warn = Nothing } - | c <- case mb_cls of - Nothing -> NE.toList h2010_dflt_clss - Just cls -> [cls] - ] - -- Report an error on multiple default declarations for the same class in the same module. - -- See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module - reportDuplicates _ (num_cls :| _) decls@((_, L locn _, _) :| _) - = setSrcSpan (locA locn) (addErrTc $ dupDefaultDeclErr cls (sndOf3 <$> decls)) - >> pure [] + toClassDefaults :: NonEmpty Class -> [LDefaultDecl GhcRn] -> TcM [LocatedA ClassDefaults] + toClassDefaults h2010_dflt_clss dfs = do + dfs <- mapMaybeM (declarationParts h2010_dflt_clss) dfs + return $ concatMap (go False) dfs where - cls = fromMaybe num_cls $ firstJusts (fmap fstOf3 decls) + go h98 = \case + (Nothing, rn_decl, tys) -> concatMap (go True) [(Just cls, rn_decl, tys) | cls <- NE.toList h2010_dflt_clss] + (Just cls, (L locn _), tys) -> [(L locn $ ClassDefaults cls tys (DP_Local (locA locn) h98) Nothing)] + +-- | Extend the default environment with the local default declarations +-- and do the action in the extended environment. +extendDefaultEnvWithLocalDefaults :: [LocatedA ClassDefaults] -> TcM a -> TcM a +extendDefaultEnvWithLocalDefaults decls action = do + tcg_env <- getGblEnv + let default_env = tcg_default tcg_env + new_default_env <- insertDefaultDecls default_env decls + updGblEnv (\gbl -> gbl { tcg_default = new_default_env } ) $ action + +-- | Insert local default declarations into the default environment. +-- +-- See 'insertDefaultDecl'. +insertDefaultDecls :: DefaultEnv -> [LocatedA ClassDefaults] -> TcM DefaultEnv +insertDefaultDecls = foldrM insertDefaultDecl +-- | Insert a local default declaration into the default environment. +-- +-- If the class already has a local default declaration in the DefaultEnv, +-- report an error and return the original DefaultEnv. Otherwise, override +-- any existing default declarations (e.g. imported default declarations). +-- +-- See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module +insertDefaultDecl :: LocatedA ClassDefaults -> DefaultEnv -> TcM DefaultEnv +insertDefaultDecl (L decl_loc new_cls_defaults ) default_env = + case lookupDefaultEnv default_env (className cls) of + Just cls_defaults + | DP_Local {} <- cd_provenance cls_defaults + -> do { setSrcSpan (locA decl_loc) (addErrTc $ TcRnMultipleDefaultDeclarations cls cls_defaults) + ; return default_env } + _ -> return $ insertDefaultEnv new_cls_defaults default_env + -- NB: this overrides imported and built-in default declarations + -- for this class, if there were any. + where + cls = cd_class new_cls_defaults + -- | Check that the type is an instance of at least one of the default classes. -- @@ -289,10 +309,6 @@ simplifyDefault cls dflt_ty@(L l _) -> Nothing } -dupDefaultDeclErr :: Class -> NonEmpty (LDefaultDecl GhcRn) -> TcRnMessage -dupDefaultDeclErr cls (L _ DefaultDecl {} :| dup_things) - = TcRnMultipleDefaultDeclarations cls dup_things - {- Note [Instance check for default declarations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When we see a named default declaration, such as: @@ -327,4 +343,4 @@ whether each type is an instance of: - ... or the IsString class, with -XOverloadedStrings - ... or any of the Show, Eq, Ord, Foldable, and Traversable classes, with -XExtendedDefaultRules --} \ No newline at end of file +-} ===================================== compiler/GHC/Tc/Gen/Export.hs ===================================== @@ -282,7 +282,7 @@ example, would import the above `default IsString (Text, String)` declaration into the importing module. -The `cd_module` field of `ClassDefaults` tracks the module whence the default was +The `cd_provenance` field of `ClassDefaults` tracks the module whence the default was imported from, for the purpose of warning reports. The said warning report may be triggered by `-Wtype-defaults` or by a user-defined `WARNING` pragma attached to the default export. In the latter case the warning text is stored in the ===================================== compiler/GHC/Tc/Module.hs ===================================== @@ -383,6 +383,7 @@ the actual contents of the module are wired in to GHC. -} {- Note [Disambiguation of multiple default declarations] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See Note [Named default declarations] in GHC.Tc.Gen.Default @@ -1811,9 +1812,8 @@ tcTyClsInstDecls tycl_decls deriv_decls default_decls binds -- -- But only after we've typechecked 'default' declarations. -- See Note [Typechecking default declarations] - defaults <- tcDefaults default_decls ; - updGblEnv (\gbl -> gbl { tcg_default = defaults }) $ do { - + defaults <- tcDefaultDecls default_decls + ; extendDefaultEnvWithLocalDefaults defaults $ do { -- Careful to quit now in case there were instance errors, so that -- the deriving errors don't pile up as well. ===================================== compiler/GHC/Tc/Utils/Env.hs ===================================== @@ -128,8 +128,7 @@ import GHC.Types.SourceFile import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Env -import GHC.Types.DefaultEnv ( DefaultEnv, ClassDefaults(..), - defaultEnv, emptyDefaultEnv, lookupDefaultEnv, unitDefaultEnv ) +import GHC.Types.DefaultEnv import GHC.Types.Error import GHC.Types.Id import GHC.Types.Id.Info ( RecSelParent(..) ) @@ -971,21 +970,28 @@ isBrackStage _other = False ************************************************************************ -} -{- Note [Default class defaults] +{- Note [Builtin class defaults] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -In absence of user-defined `default` declarations, the set of class defaults in -effect (i.e. `DefaultEnv`) is determined by the absence or -presence of the `ExtendedDefaultRules` and `OverloadedStrings` extensions. In their -absence, the only rule in effect is `default Num (Integer, Double)` as specified by -Haskell Language Report. - -In GHC's internal packages `DefaultEnv` is empty to minimize cross-module dependencies: -the `Num` class or `Integer` type may not even be available in low-level modules. If -you don't do this, attempted defaulting in package ghc-prim causes an actual crash -(attempting to look up the `Integer` type). - -A user-defined `default` declaration overrides the defaults for the specified class, -and only for that class. +In the absence of user-defined `default` declarations, the set of class defaults in +effect (i.e. the `DefaultEnv`) depends on whether the `ExtendedDefaultRules` and +`OverloadedStrings` extensions are enabled. In their absence, the only rule in effect +is `default Num (Integer, Double)`, as specified by the Haskell 2010 report. + +Remark [No built-in defaults in ghc-internal] + + When typechecking the ghc-internal package, we **do not** include any built-in + defaults. This is because, in ghc-internal, types such as 'Num' or 'Integer' may + not even be available (they haven't been typechecked yet). + +Remark [default () in ghc-internal] + + Historically, modules inside ghc-internal have used a single default declaration, + of the form `default ()`, to work around the problem described in + Remark [No built-in defaults in ghc-internal]. + + When we typecheck such a default declaration, we must also make sure not to fail + if e.g. 'Num' is not in scope. We thus have special treatment for this case, + in 'GHC.Tc.Gen.Default.tcDefaultDecls'. -} tcGetDefaultTys :: TcM (DefaultEnv, -- Default classes and types @@ -997,7 +1003,7 @@ tcGetDefaultTys -- See also #1974 builtinDefaults cls tys = ClassDefaults{ cd_class = cls , cd_types = tys - , cd_module = Nothing + , cd_provenance = DP_Builtin , cd_warn = Nothing } -- see Note [Named default declarations] in GHC.Tc.Gen.Default @@ -1005,7 +1011,8 @@ tcGetDefaultTys ; this_module <- tcg_mod <$> getGblEnv ; let this_unit = moduleUnit this_module ; if this_unit == ghcInternalUnit - -- see Note [Default class defaults] + -- see Remark [No built-in defaults in ghc-internal] + -- in Note [Builtin class defaults] in GHC.Tc.Utils.Env then return (defaults, extended_defaults) else do -- not one of the built-in units @@ -1037,6 +1044,8 @@ tcGetDefaultTys } -- The Num class is already user-defaulted, no need to construct the builtin default _ -> pure emptyDefaultEnv + -- Supply the built-in defaults, but make the user-supplied defaults + -- override them. ; let deflt_tys = mconcat [ extDef, numDef, ovlStr, defaults ] ; return (deflt_tys, extended_defaults) } } ===================================== compiler/GHC/Types/DefaultEnv.hs ===================================== @@ -1,7 +1,9 @@ {-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE LambdaCase #-} module GHC.Types.DefaultEnv ( ClassDefaults (..) + , DefaultProvenance (..) , DefaultEnv , emptyDefaultEnv , isEmptyDefaultEnv @@ -12,6 +14,8 @@ module GHC.Types.DefaultEnv , defaultList , plusDefaultEnv , mkDefaultEnv + , insertDefaultEnv + , isHaskell2010Default ) where @@ -22,6 +26,7 @@ import GHC.Tc.Utils.TcType (Type) import GHC.Types.Name (Name, nameUnique, stableNameCmp) import GHC.Types.Name.Env import GHC.Types.Unique.FM (lookupUFM_Directly) +import GHC.Types.SrcLoc (SrcSpan) import GHC.Unit.Module.Warnings (WarningTxt) import GHC.Unit.Types (Module) import GHC.Utils.Outputable @@ -37,13 +42,73 @@ import Data.Function (on) -- NB: this includes Haskell98 default declarations, at the 'Num' key. type DefaultEnv = NameEnv ClassDefaults +{- Note [DefaultProvenance] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Each `ClassDefault` is annotated with its `DefaultProvenance`, which +says where the default came from. Specifically +* `DP_Local loc h98`: the default came from an explicit `default` declaration in the module + being compiled, at location `loc`, and the boolean `h98` indicates whether + it was from a Haskell 98 default declaration (e.g. `default (Int, Double)`). +* `DP_Imported M`: the default was imported, it is explicitly exported by module `M`. +* `DP_Builtin`: the default was automatically provided by GHC. + see Note [Builtin class defaults] in GHC.Tc.Utils.Env + +These annotations are used to disambiguate multiple defaults for the same class. +For example, consider the following modules: + + module M( default C ) where { default C( ... ) } + module M2( default C) where { import M } + module N( default C () where { default C(... ) } + + module A where { import M2 } + module B where { import M2; import N } + module A1 where { import N; default C ( ... ) } + module B2 where { default C ( ... ); default C ( ... ) } + +When compiling N, the default for C is annotated with DP_Local loc. +When compiling M2, the default for C is annotated with DP_Local M. +When compiling A, the default for C is annotated with DP_Imported M2. + +Cases we needed to disambiguate: + * Compiling B, two defaults for C: DP_Imported M2, DP_Imported N. + * Compiling A1, two defaults for C: DP_Imported N, DP_Local loc. + * Compiling B2, two defaults for C: DP_Local loc1, DP_Local loc2. + +For how we disambiguate these cases, +See Note [Disambiguation of multiple default declarations] in GHC.Tc.Module. +-} + +-- | The provenance of a collection of default types for a class. +-- see Note [DefaultProvenance] for more details +data DefaultProvenance + -- | A locally defined default declaration. + = DP_Local + { defaultDeclLoc :: SrcSpan -- ^ The 'SrcSpan' of the default declaration + , defaultDeclH98 :: Bool -- ^ Is this a Haskell 98 default declaration? + } + -- | Built-in class defaults. + | DP_Builtin + -- | Imported class defaults. + | DP_Imported Module -- ^ The module from which the defaults were imported + deriving (Eq, Data) + +instance Outputable DefaultProvenance where + ppr (DP_Local loc h98) = ppr loc <> (if h98 then text " (H98)" else empty) + ppr DP_Builtin = text "built-in" + ppr (DP_Imported mod) = ppr mod + +isHaskell2010Default :: DefaultProvenance -> Bool +isHaskell2010Default = \case + DP_Local { defaultDeclH98 = isH98 } -> isH98 + DP_Builtin -> True + DP_Imported {} -> False + -- | Defaulting type assignments for the given class. data ClassDefaults = ClassDefaults { cd_class :: Class -- ^ The class whose defaults are being defined , cd_types :: [Type] - , cd_module :: Maybe Module - -- ^ @Nothing@ for built-in, - -- @Just@ the current module or the module whence the default was imported + , cd_provenance :: DefaultProvenance + -- ^ Where the defaults came from -- see Note [Default exports] in GHC.Tc.Gen.Export , cd_warn :: Maybe (WarningTxt GhcRn) -- ^ Warning emitted when the default is used @@ -70,6 +135,9 @@ defaultList :: DefaultEnv -> [ClassDefaults] defaultList = sortBy (stableNameCmp `on` className . cd_class) . nonDetNameEnvElts -- sortBy recovers determinism +insertDefaultEnv :: ClassDefaults -> DefaultEnv -> DefaultEnv +insertDefaultEnv d env = extendNameEnv env (className $ cd_class d) d + lookupDefaultEnv :: DefaultEnv -> Name -> Maybe ClassDefaults lookupDefaultEnv env = lookupUFM_Directly env . nameUnique ===================================== libraries/template-haskell/Language/Haskell/TH/Syntax.hs ===================================== @@ -1,6 +1,6 @@ {-# LANGUAGE MagicHash #-} {-# LANGUAGE TemplateHaskellQuotes #-} -{-# LANGUAGE Trustworthy #-} +{-# LANGUAGE Safe #-} {-# LANGUAGE UnboxedTuples #-} module Language.Haskell.TH.Syntax ( @@ -190,16 +190,11 @@ module Language.Haskell.TH.Syntax ( nothingName, rightName, trueName, - addrToByteArrayName, - addrToByteArray, ) where -import Data.Array.Byte import GHC.Boot.TH.Lift import GHC.Boot.TH.Syntax -import GHC.Exts -import GHC.ST import System.FilePath -- This module completely re-exports 'GHC.Boot.TH.Syntax', @@ -211,17 +206,3 @@ makeRelativeToProject fp | isRelative fp = do root <- getPackageRoot return (root </> fp) makeRelativeToProject fp = return fp - --- The following two defintions are copied from 'Data.Byte.Array' --- in order to preserve the old export list of 'TH.Syntax'. --- They will soon be removed as part of #24782. - -addrToByteArrayName :: Name -addrToByteArrayName = 'addrToByteArray - -addrToByteArray :: Int -> Addr# -> ByteArray -addrToByteArray (I# len) addr = runST $ ST $ - \s -> case newByteArray# len s of - (# s', mb #) -> case copyAddrToByteArray# addr mb 0# len s' of - s'' -> case unsafeFreezeByteArray# mb s'' of - (# s''', ret #) -> (# s''', ByteArray ret #) ===================================== libraries/template-haskell/changelog.md ===================================== @@ -13,6 +13,8 @@ * Remove the `Language.Haskell.TH.Lib.Internal` module. This module has long been deprecated, and exposes compiler internals. Users should use `Language.Haskell.TH.Lib` instead, which exposes a stable version of this API. + + * Remove `addrToByteArrayName` and `addrToByteArray` from `Language.Haskell.TH.Syntax`. These were part of the implementation of the `Lift ByteArray` instance and were errornously exported because this module lacked an explicit export list. They have no usages on Hackage. ## 2.23.0.0 ===================================== testsuite/tests/default/T25912.hs ===================================== @@ -0,0 +1,14 @@ +{-# LANGUAGE NamedDefaults #-} + +module Main where + +import T25912_helper + +-- now we declare the default instances +-- for the classes C again to check that +-- it won't hide the default instances for class B +default C (String) + +main :: IO () +main = do + print b ===================================== testsuite/tests/default/T25912.stdout ===================================== @@ -0,0 +1 @@ +"String" ===================================== testsuite/tests/default/T25912_helper.hs ===================================== @@ -0,0 +1,17 @@ +{-# LANGUAGE NamedDefaults #-} + +module T25912_helper ( default C, C(c), default B, b ) where + +class C a where + c :: a +instance C Int where + c = 1 +instance C String where + c = "String" +default C (String) + +class B a where + b :: a +instance B String where + b = "String" +default B (String) ===================================== testsuite/tests/default/T25914.hs ===================================== @@ -0,0 +1,5 @@ +{-# LANGUAGE NamedDefaults, OverloadedStrings #-} +module NamedDefaultsNum where +import Data.String +default Num () +foo = "abc" ===================================== testsuite/tests/default/T25934.hs ===================================== @@ -0,0 +1,5 @@ +{-# LANGUAGE ExtendedDefaultRules #-} +{-# LANGUAGE NamedDefaults #-} +module T25934 where +default Num (Int) +default Show (Int) ===================================== testsuite/tests/default/all.T ===================================== @@ -39,3 +39,6 @@ test('T25858v2', [extra_files(['T25858v2_helper.hs'])], multimod_compile_and_run test('T25858v3', [extra_files(['T25858v3_helper.hs'])], multimod_compile_and_run, ['T25858v3', '']) test('T25858v4', normal, compile_and_run, ['']) test('T25882', normal, compile, ['']) +test('T25912', [extra_files(['T25912_helper.hs'])], multimod_compile_and_run, ['T25912', '']) +test('T25914', normal, compile, ['']) +test('T25934', normal, compile, ['']) ===================================== testsuite/tests/default/default-fail03.stderr ===================================== @@ -1,3 +1,4 @@ -default-fail03.hs:4:1: [GHC-99565] +default-fail03.hs:4:1: error: [GHC-99565] Multiple default declarations for class ‘Num’ - here was another default declaration default-fail03.hs:3:1-29 + conflicting named default declaration at: default-fail03.hs:3:1-29 + ===================================== testsuite/tests/interface-stability/template-haskell-exports.stdout ===================================== @@ -1369,7 +1369,7 @@ module Language.Haskell.TH.Quote where quoteFile :: QuasiQuoter -> QuasiQuoter module Language.Haskell.TH.Syntax where - -- Safety: Trustworthy + -- Safety: Safe type AnnLookup :: * data AnnLookup = AnnLookupModule Module | AnnLookupName Name type AnnTarget :: * @@ -1780,8 +1780,6 @@ module Language.Haskell.TH.Syntax where addModFinalizer :: Q () -> Q () addTempFile :: GHC.Internal.Base.String -> Q GHC.Internal.IO.FilePath addTopDecls :: [Dec] -> Q () - addrToByteArray :: GHC.Internal.Types.Int -> GHC.Internal.Prim.Addr# -> Data.Array.Byte.ByteArray - addrToByteArrayName :: Name badIO :: forall a. GHC.Internal.Base.String -> GHC.Internal.Types.IO a bindCode :: forall (m :: * -> *) a (r :: GHC.Internal.Types.RuntimeRep) (b :: TYPE r). GHC.Internal.Base.Monad m => m a -> (a -> Code m b) -> Code m b bindCode_ :: forall (m :: * -> *) a (r :: GHC.Internal.Types.RuntimeRep) (b :: TYPE r). GHC.Internal.Base.Monad m => m a -> Code m b -> Code m b ===================================== testsuite/tests/linters/notes.stdout ===================================== @@ -8,7 +8,7 @@ ref compiler/GHC/Core/Opt/Simplify/Iteration.hs:4345:8: Note [Lambda-boun ref compiler/GHC/Core/Opt/Simplify/Utils.hs:1387:37: Note [Gentle mode] ref compiler/GHC/Core/Opt/Specialise.hs:1761:29: Note [Arity decrease] ref compiler/GHC/Core/TyCo/Rep.hs:1783:31: Note [What prevents a constraint from floating] -ref compiler/GHC/Driver/DynFlags.hs:1216:52: Note [Eta-reduction in -O0] +ref compiler/GHC/Driver/DynFlags.hs:1218:52: Note [Eta-reduction in -O0] ref compiler/GHC/Driver/Main.hs:1901:34: Note [simpleTidyPgm - mkBootModDetailsTc] ref compiler/GHC/Hs/Expr.hs:189:63: Note [Pending Splices] ref compiler/GHC/Hs/Expr.hs:2194:87: Note [Lifecycle of a splice] @@ -18,10 +18,8 @@ ref compiler/GHC/Hs/Pat.hs:151:74: Note [Lifecycle of a splice] ref compiler/GHC/HsToCore/Pmc/Solver.hs:860:20: Note [COMPLETE sets on data families] ref compiler/GHC/HsToCore/Quote.hs:1533:7: Note [How brackets and nested splices are handled] ref compiler/GHC/Stg/Unarise.hs:457:32: Note [Renaming during unarisation] -ref compiler/GHC/Tc/Gen/Default.hs:87:6: Note [Disambiguation of multiple default declarations] -ref compiler/GHC/Tc/Gen/Default.hs:193:11: Note [Disambiguation of multiple default declarations] ref compiler/GHC/Tc/Gen/HsType.hs:563:56: Note [Skolem escape prevention] -ref compiler/GHC/Tc/Gen/HsType.hs:2693:7: Note [Matching a kind signature with a declaration] +ref compiler/GHC/Tc/Gen/HsType.hs:2717:7: Note [Matching a kind signature with a declaration] ref compiler/GHC/Tc/Gen/Pat.hs:284:20: Note [Typing patterns in pattern bindings] ref compiler/GHC/Tc/Gen/Pat.hs:1378:7: Note [Matching polytyped patterns] ref compiler/GHC/Tc/Gen/Sig.hs:91:10: Note [Overview of type signatures] @@ -30,8 +28,6 @@ ref compiler/GHC/Tc/Gen/Splice.hs:543:35: Note [PendingRnSplice] ref compiler/GHC/Tc/Gen/Splice.hs:670:7: Note [How brackets and nested splices are handled] ref compiler/GHC/Tc/Gen/Splice.hs:909:11: Note [How brackets and nested splices are handled] ref compiler/GHC/Tc/Instance/Family.hs:458:35: Note [Constrained family instances] -ref compiler/GHC/Tc/Module.hs:385:3: Note [Disambiguation of multiple default declarations] -ref compiler/GHC/Tc/Module.hs:420:7: Note [Disambiguation of multiple default declarations] ref compiler/GHC/Tc/Solver/Rewrite.hs:1015:7: Note [Stability of rewriting] ref compiler/GHC/Tc/TyCl.hs:1322:6: Note [Unification variables need fresh Names] ref compiler/GHC/Tc/Types/Constraint.hs:209:9: Note [NonCanonical Semantics] ===================================== testsuite/tests/module/mod58.stderr ===================================== @@ -1,4 +1,4 @@ - mod58.hs:4:1: error: [GHC-99565] Multiple default declarations for class ‘Num’ - here was another default declaration mod58.hs:3:1-21 + conflicting default declaration at: mod58.hs:3:1-21 + View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/e08a689a75c44fcf8cc924d30eb1c2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/e08a689a75c44fcf8cc924d30eb1c2… You're receiving this email because of your account on gitlab.haskell.org.

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