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author | Simon Peyton Jones <simonpj@microsoft.com> | 2022-11-09 10:33:22 +0000 |
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committer | Simon Peyton Jones <simon.peytonjones@gmail.com> | 2022-11-11 23:40:10 +0000 |
commit | 778c6adca2c995cd8a1b84394d4d5ca26b915dac (patch) | |
tree | 17350cc63ae04a5b15461771304d195c30ada2f7 /compiler/GHC/Tc/Errors.hs | |
parent | 154c70f6c589aa6531cbeea4aa3ec06e0acaf690 (diff) | |
download | haskell-778c6adca2c995cd8a1b84394d4d5ca26b915dac.tar.gz |
Type vs Constraint: finally nailed
This big patch addresses the rats-nest of issues that have plagued
us for years, about the relationship between Type and Constraint.
See #11715/#21623.
The main payload of the patch is:
* To introduce CONSTRAINT :: RuntimeRep -> Type
* To make TYPE and CONSTRAINT distinct throughout the compiler
Two overview Notes in GHC.Builtin.Types.Prim
* Note [TYPE and CONSTRAINT]
* Note [Type and Constraint are not apart]
This is the main complication.
The specifics
* New primitive types (GHC.Builtin.Types.Prim)
- CONSTRAINT
- ctArrowTyCon (=>)
- tcArrowTyCon (-=>)
- ccArrowTyCon (==>)
- funTyCon FUN -- Not new
See Note [Function type constructors and FunTy]
and Note [TYPE and CONSTRAINT]
* GHC.Builtin.Types:
- New type Constraint = CONSTRAINT LiftedRep
- I also stopped nonEmptyTyCon being built-in; it only needs to be wired-in
* Exploit the fact that Type and Constraint are distinct throughout GHC
- Get rid of tcView in favour of coreView.
- Many tcXX functions become XX functions.
e.g. tcGetCastedTyVar --> getCastedTyVar
* Kill off Note [ForAllTy and typechecker equality], in (old)
GHC.Tc.Solver.Canonical. It said that typechecker-equality should ignore
the specified/inferred distinction when comparein two ForAllTys. But
that wsa only weakly supported and (worse) implies that we need a separate
typechecker equality, different from core equality. No no no.
* GHC.Core.TyCon: kill off FunTyCon in data TyCon. There was no need for it,
and anyway now we have four of them!
* GHC.Core.TyCo.Rep: add two FunTyFlags to FunCo
See Note [FunCo] in that module.
* GHC.Core.Type. Lots and lots of changes driven by adding CONSTRAINT.
The key new function is sORTKind_maybe; most other changes are built
on top of that.
See also `funTyConAppTy_maybe` and `tyConAppFun_maybe`.
* Fix a longstanding bug in GHC.Core.Type.typeKind, and Core Lint, in
kinding ForAllTys. See new tules (FORALL1) and (FORALL2) in GHC.Core.Type.
(The bug was that before (forall (cv::t1 ~# t2). blah), where
blah::TYPE IntRep, would get kind (TYPE IntRep), but it should be
(TYPE LiftedRep). See Note [Kinding rules for types] in GHC.Core.Type.
* GHC.Core.TyCo.Compare is a new module in which we do eqType and cmpType.
Of course, no tcEqType any more.
* GHC.Core.TyCo.FVs. I moved some free-var-like function into this module:
tyConsOfType, visVarsOfType, and occCheckExpand. Refactoring only.
* GHC.Builtin.Types. Compiletely re-engineer boxingDataCon_maybe to
have one for each /RuntimeRep/, rather than one for each /Type/.
This dramatically widens the range of types we can auto-box.
See Note [Boxing constructors] in GHC.Builtin.Types
The boxing types themselves are declared in library ghc-prim:GHC.Types.
GHC.Core.Make. Re-engineer the treatment of "big" tuples (mkBigCoreVarTup
etc) GHC.Core.Make, so that it auto-boxes unboxed values and (crucially)
types of kind Constraint. That allows the desugaring for arrows to work;
it gathers up free variables (including dictionaries) into tuples.
See Note [Big tuples] in GHC.Core.Make.
There is still work to do here: #22336. But things are better than
before.
* GHC.Core.Make. We need two absent-error Ids, aBSENT_ERROR_ID for types of
kind Type, and aBSENT_CONSTRAINT_ERROR_ID for vaues of kind Constraint.
Ditto noInlineId vs noInlieConstraintId in GHC.Types.Id.Make;
see Note [inlineId magic].
* GHC.Core.TyCo.Rep. Completely refactor the NthCo coercion. It is now called
SelCo, and its fields are much more descriptive than the single Int we used to
have. A great improvement. See Note [SelCo] in GHC.Core.TyCo.Rep.
* GHC.Core.RoughMap.roughMatchTyConName. Collapse TYPE and CONSTRAINT to
a single TyCon, so that the rough-map does not distinguish them.
* GHC.Core.DataCon
- Mainly just improve documentation
* Some significant renamings:
GHC.Core.Multiplicity: Many --> ManyTy (easier to grep for)
One --> OneTy
GHC.Core.TyCo.Rep TyCoBinder --> GHC.Core.Var.PiTyBinder
GHC.Core.Var TyCoVarBinder --> ForAllTyBinder
AnonArgFlag --> FunTyFlag
ArgFlag --> ForAllTyFlag
GHC.Core.TyCon TyConTyCoBinder --> TyConPiTyBinder
Many functions are renamed in consequence
e.g. isinvisibleArgFlag becomes isInvisibleForAllTyFlag, etc
* I refactored FunTyFlag (was AnonArgFlag) into a simple, flat data type
data FunTyFlag
= FTF_T_T -- (->) Type -> Type
| FTF_T_C -- (-=>) Type -> Constraint
| FTF_C_T -- (=>) Constraint -> Type
| FTF_C_C -- (==>) Constraint -> Constraint
* GHC.Tc.Errors.Ppr. Some significant refactoring in the TypeEqMisMatch case
of pprMismatchMsg.
* I made the tyConUnique field of TyCon strict, because I
saw code with lots of silly eval's. That revealed that
GHC.Settings.Constants.mAX_SUM_SIZE can only be 63, because
we pack the sum tag into a 6-bit field. (Lurking bug squashed.)
Fixes
* #21530
Updates haddock submodule slightly.
Performance changes
~~~~~~~~~~~~~~~~~~~
I was worried that compile times would get worse, but after
some careful profiling we are down to a geometric mean 0.1%
increase in allocation (in perf/compiler). That seems fine.
There is a big runtime improvement in T10359
Metric Decrease:
LargeRecord
MultiLayerModulesTH_OneShot
T13386
T13719
Metric Increase:
T8095
Diffstat (limited to 'compiler/GHC/Tc/Errors.hs')
-rw-r--r-- | compiler/GHC/Tc/Errors.hs | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/compiler/GHC/Tc/Errors.hs b/compiler/GHC/Tc/Errors.hs index 021d163d84..77e7b96f9c 100644 --- a/compiler/GHC/Tc/Errors.hs +++ b/compiler/GHC/Tc/Errors.hs @@ -1,11 +1,11 @@ {-# LANGUAGE LambdaCase #-} {-# LANGUAGE NamedFieldPuns #-} +{-# LANGUAGE ParallelListComp #-} {-# LANGUAGE ScopedTypeVariables #-} {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-} {-# OPTIONS_GHC -Wno-incomplete-record-updates #-} -{-# LANGUAGE ParallelListComp #-} module GHC.Tc.Errors( reportUnsolved, reportAllUnsolved, warnAllUnsolved, @@ -60,8 +60,7 @@ import qualified GHC.LanguageExtensions as LangExt import GHC.Core.Predicate import GHC.Core.Type import GHC.Core.Coercion -import GHC.Core.TyCo.Ppr ( pprTyVars - ) +import GHC.Core.TyCo.Ppr ( pprTyVars ) import GHC.Core.InstEnv import GHC.Core.TyCon import GHC.Core.DataCon @@ -672,7 +671,7 @@ reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics is_user_type_error item _ = isUserTypeError (errorItemPred item) is_homo_equality _ (EqPred _ ty1 ty2) - = tcTypeKind ty1 `tcEqType` tcTypeKind ty2 + = typeKind ty1 `tcEqType` typeKind ty2 is_homo_equality _ _ = False @@ -1098,7 +1097,7 @@ addDeferredBinding ctxt err (EI { ei_evdest = Just dest, ei_pred = item_ty -> do { -- See Note [Deferred errors for coercion holes] let co_var = coHoleCoVar hole ; addTcEvBind ev_binds_var $ mkWantedEvBind co_var err_tm - ; fillCoercionHole hole (mkTcCoVarCo co_var) } } + ; fillCoercionHole hole (mkCoVarCo co_var) } } addDeferredBinding _ _ _ = return () -- Do not set any evidence for Given mkErrorTerm :: SolverReportErrCtxt -> CtLoc -> Type -- of the error term @@ -1647,9 +1646,9 @@ mkEqErr_help :: SolverReportErrCtxt -> ErrorItem -> TcType -> TcType -> TcM (TcSolverReportMsg, [GhcHint]) mkEqErr_help ctxt item ty1 ty2 - | Just casted_tv1 <- tcGetCastedTyVar_maybe ty1 + | Just casted_tv1 <- getCastedTyVar_maybe ty1 = mkTyVarEqErr ctxt item casted_tv1 ty2 - | Just casted_tv2 <- tcGetCastedTyVar_maybe ty2 + | Just casted_tv2 <- getCastedTyVar_maybe ty2 = mkTyVarEqErr ctxt item casted_tv2 ty1 | otherwise = do @@ -1803,7 +1802,7 @@ mkTyVarEqErr' ctxt item (tv1, co1) ty2 , Implic { ic_tclvl = lvl } <- implic = assertPpr (not (isTouchableMetaTyVar lvl tv1)) (ppr tv1 $$ ppr lvl) $ do -- See Note [Error messages for untouchables] - tv_extra <- extraTyVarEqInfo (tv1, Just implic) ty2 + tv_extra <- extraTyVarEqInfo (tv1, Just implic) ty2 let tv_extra' = tv_extra { thisTyVarIsUntouchable = Just implic } msg = Mismatch { mismatchMsg = mismatch_msg @@ -1969,7 +1968,7 @@ extraTyVarEqInfo (tv1, mb_implic) ty2 , thisTyVarIsUntouchable = mb_implic , otherTy = ty2_info } where - ty_extra ty = case tcGetCastedTyVar_maybe ty of + ty_extra ty = case getCastedTyVar_maybe ty of Just (tv, _) -> Just <$> extraTyVarInfo tv Nothing -> return Nothing @@ -1991,7 +1990,7 @@ suggestAddSig ctxt ty1 _ty2 = Nothing where inferred_bndrs = - case tcGetTyVar_maybe ty1 of + case getTyVar_maybe ty1 of Just tv | isSkolemTyVar tv -> find (cec_encl ctxt) False tv _ -> [] @@ -2024,8 +2023,7 @@ mkMismatchMsg item ty1 ty2 = KindEqOrigin cty1 cty2 sub_o mb_sub_t_or_k -> (mkBasicMismatchMsg NoEA item ty1 ty2) { mismatch_whenMatching = Just $ WhenMatching cty1 cty2 sub_o mb_sub_t_or_k - , mismatch_mb_same_occ = mb_same_occ - } + , mismatch_mb_same_occ = mb_same_occ } _ -> (mkBasicMismatchMsg NoEA item ty1 ty2) { mismatch_mb_same_occ = mb_same_occ } |