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authorSimon Peyton Jones <simonpj@microsoft.com>2022-11-09 10:33:22 +0000
committerSimon Peyton Jones <simon.peytonjones@gmail.com>2022-11-11 23:40:10 +0000
commit778c6adca2c995cd8a1b84394d4d5ca26b915dac (patch)
tree17350cc63ae04a5b15461771304d195c30ada2f7 /testsuite/tests/polykinds
parent154c70f6c589aa6531cbeea4aa3ec06e0acaf690 (diff)
downloadhaskell-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 'testsuite/tests/polykinds')
-rw-r--r--testsuite/tests/polykinds/T14172.stderr3
-rw-r--r--testsuite/tests/polykinds/T14265.stderr3
2 files changed, 2 insertions, 4 deletions
diff --git a/testsuite/tests/polykinds/T14172.stderr b/testsuite/tests/polykinds/T14172.stderr
index d79af1f7c0..df3868fb6c 100644
--- a/testsuite/tests/polykinds/T14172.stderr
+++ b/testsuite/tests/polykinds/T14172.stderr
@@ -8,7 +8,8 @@ T14172.hs:7:46: error: [GHC-88464]
To use the inferred type, enable PartialTypeSignatures
• In the first argument of ‘h’, namely ‘_’
In the first argument of ‘f’, namely ‘(h _)’
- In the type ‘(a -> f b) -> g a -> f (h _)’
+ In the type signature:
+ traverseCompose :: (a -> f b) -> g a -> f (h _)
T14172.hs:8:19: error: [GHC-25897]
• Couldn't match type ‘a’ with ‘g'1 a'0’
diff --git a/testsuite/tests/polykinds/T14265.stderr b/testsuite/tests/polykinds/T14265.stderr
index 7f782ff8fc..fad85e9696 100644
--- a/testsuite/tests/polykinds/T14265.stderr
+++ b/testsuite/tests/polykinds/T14265.stderr
@@ -6,7 +6,6 @@ T14265.hs:7:12: error: [GHC-88464]
at T14265.hs:8:1-8
To use the inferred type, enable PartialTypeSignatures
• In the first argument of ‘proxy’, namely ‘_’
- In the type ‘proxy _ -> ()’
In the type signature: f :: proxy _ -> ()
T14265.hs:10:15: error: [GHC-88464]
@@ -16,7 +15,6 @@ T14265.hs:10:15: error: [GHC-88464]
at T14265.hs:11:1-15
To use the inferred type, enable PartialTypeSignatures
• In the first argument of ‘StateT’, namely ‘_’
- In the type ‘StateT _ _ ()’
In the type signature: foo :: StateT _ _ ()
T14265.hs:10:17: error: [GHC-88464]
@@ -26,5 +24,4 @@ T14265.hs:10:17: error: [GHC-88464]
at T14265.hs:11:1-15
To use the inferred type, enable PartialTypeSignatures
• In the second argument of ‘StateT’, namely ‘_’
- In the type ‘StateT _ _ ()’
In the type signature: foo :: StateT _ _ ()