Vladislav Zavialov authored 1 year ago and Marge Bot committed 1 year ago

Numerous tests make use of CUSKs (complete user-supplied kinds),
a legacy feature scheduled for deprecation. In order to proceed
with the said deprecation, the tests have been updated to use SAKS
instead (standalone kind signatures).

This also allows us to remove the Haskell2010 language pragmas that
were added in 115cd3c8 to work around the lack of CUSKs in GHC2021.

This patch modifies the renamer to respect ScopedTypeVariables in kind
signatures. This means that kind variables bound by the outermost
`forall` now scope over the type:

  type F = '[Right @a @() () :: forall a. Either a ()]
  --         ^^^^^^^^^^^^^^^          ^^^
  --          in scope here        bound here

However, any use of such variables is a type error, because we don't
have type-level lambdas to bind them in Core. This is described in the
new Note [Type variable scoping errors during type check] in GHC.Tc.Types.

Krzysztof Gogolewski authored 1 year ago and Marge Bot committed 1 year ago

Fixes #23176

This patch implements @k-binders introduced in GHC Proposal #425
and guarded behind the TypeAbstractions extension:

	type D :: forall k j. k -> j -> Type
	data D @k @j a b = ...
	       ^^ ^^

To represent the new syntax, we modify LHsQTyVars as follows:

	-  hsq_explicit :: [LHsTyVarBndr () pass]
	+  hsq_explicit :: [LHsTyVarBndr (HsBndrVis pass) pass]

HsBndrVis is a new data type that records the distinction between
type variable binders written with and without the @ sign:

	data HsBndrVis pass
	  = HsBndrRequired
	  | HsBndrInvisible (LHsToken "@" pass)

The rest of the patch updates GHC, template-haskell, and haddock
to handle the new syntax.

Parser:
  The PsErrUnexpectedTypeAppInDecl error message is removed.
  The syntax it used to reject is now permitted.

Renamer:
  The @ sign does not affect the scope of a binder, so the changes to
  the renamer are minimal.  See rnLHsTyVarBndrVisFlag.

Type checker:
  There are three code paths that were updated to deal with the newly
  introduced invisible type variable binders:

    1. checking SAKS: see kcCheckDeclHeader_sig, matchUpSigWithDecl
    2. checking CUSK: see kcCheckDeclHeader_cusk
    3. inference: see kcInferDeclHeader, rejectInvisibleBinders

  Helper functions bindExplicitTKBndrs_Q_Skol and bindExplicitTKBndrs_Q_Tv
  are generalized to work with HsBndrVis.

Updates the haddock submodule.

Metric Increase:
    MultiLayerModulesTH_OneShot

Co-authored-by: Simon Peyton Jones <simon.peytonjones@gmail.com>

Hai Nguyen Quang authored 1 year ago and Marge Bot committed 1 year ago

This patch migrates the error messages in GHC.Tc.Validity to use
the new diagnostic infrastructure.

It adds the constructors:

  - TcRnSimplifiableConstraint
  - TcRnArityMismatch
  - TcRnIllegalInstanceDecl, with sub-datatypes for HasField errors
    and fundep coverage condition errors.

Simon Peyton Jones authored 1 year ago and Marge Bot committed 1 year ago

This patch continues the refactoring of the constraint solver
described in #23070.

The Big Deal in this patch is to call the regular, eager unifier from the
constraint solver, when we want to create new equalities. This
replaces the existing, unifyWanted which amounted to
yet-another-unifier, so it reduces duplication of a rather subtle
piece of technology. See

  * Note [The eager unifier] in GHC.Tc.Utils.Unify
  * GHC.Tc.Solver.Monad.wrapUnifierTcS

I did lots of other refactoring along the way

* I simplified the treatment of right hand sides that contain CoercionHoles.
  Now, a constraint that contains a hetero-kind CoercionHole is non-canonical,
  and cannot be used for rewriting or unification alike.  This required me
  to add the ch_hertero_kind flag to CoercionHole, with consequent knock-on
  effects. See wrinkle (2) of `Note [Equalities with incompatible kinds]` in
  GHC.Tc.Solver.Equality.

* I refactored the StopOrContinue type to add StartAgain, so that after a
  fundep improvement (for example) we can simply start the pipeline again.

* I got rid of the unpleasant (and inefficient) rewriterSetFromType/Co functions.
  With Richard I concluded that they are never needed.

* I discovered Wrinkle (W1) in Note [Wanteds rewrite Wanteds] in
  GHC.Tc.Types.Constraint, and therefore now prioritise non-rewritten equalities.

Quite a few error messages change, I think always for the better.

Compiler runtime stays about the same, with one outlier: a 17% improvement in T17836

Metric Decrease:
    T17836
    T18223

Torsten Schmits authored 1 year ago and Marge Bot committed 1 year ago

Tracking ticket: #20115

MR: !10361

This converts uses of `mkTcRnUnknownMessage` to newly added constructors
of `TcRnMessage`.

Only addresses the single warning missing from the previous MR.

Torsten Schmits authored 1 year ago and Torsten Schmits committed 1 year ago

Tracking ticket: #20115

MR: !10350

This converts uses of `mkTcRnUnknownMessage` to newly added constructors
of `TcRnMessage`.

Simon Peyton Jones authored 2 years ago and Krzysztof Gogolewski committed 1 year ago

This MR substantially refactors the way in which the constraint
solver deals with equality constraints.  The big thing is:

* Intead of a pipeline in which we /first/ canonicalise and /then/
  interact (the latter including performing unification) the two steps
  are more closely integreated into one.  That avoids the current
  rather indirect communication between the two steps.

The proximate cause for this refactoring is fixing #22194, which involve
solving   [W] alpha[2] ~ Maybe (F beta[4])
by doing this:
          alpha[2] := Maybe delta[2]
          [W] delta[2] ~ F beta[4]
That is, we don't promote beta[4]!  This is very like introducing a cycle
breaker, and was very awkward to do before, but now it is all nice.
See GHC.Tc.Utils.Unify Note [Promotion and level-checking] and
Note [Family applications in canonical constraints].

The big change is this:

* Several canonicalisation checks (occurs-check, cycle-breaking,
  checking for concreteness) are combined into one new function:
     GHC.Tc.Utils.Unify.checkTyEqRhs

  This function is controlled by `TyEqFlags`, which says what to do
  for foralls, type families etc.

* `canEqCanLHSFinish` now sees if unification is possible, and if so,
  actually does it: see `canEqCanLHSFinish_try_unification`.

There are loads of smaller changes:

* The on-the-fly unifier `GHC.Tc.Utils.Unify.unifyType` has a
  cheap-and-cheerful version of `checkTyEqRhs`, called
  `simpleUnifyCheck`.  If `simpleUnifyCheck` succeeds, it can unify,
  otherwise it defers by emitting a constraint. This is simpler than
  before.

* I simplified the swapping code in `GHC.Tc.Solver.Equality.canEqCanLHS`.
  Especially the nasty stuff involving `swap_for_occurs` and
  `canEqTyVarFunEq`.  Much nicer now.  See
      Note [Orienting TyVarLHS/TyFamLHS]
      Note [Orienting TyFamLHS/TyFamLHS]

* Added `cteSkolemOccurs`, `cteConcrete`, and `cteCoercionHole` to the
  problems that can be discovered by `checkTyEqRhs`.

* I fixed #23199 `pickQuantifiablePreds`, which actually allows GHC to
  to accept both cases in #22194 rather than rejecting both.

Yet smaller:

* Added a `synIsConcrete` flag to `SynonymTyCon` (alongside `synIsFamFree`)
  to reduce the need for synonym expansion when checking concreteness.
  Use it in `isConcreteType`.

* Renamed `isConcrete` to `isConcreteType`

* Defined `GHC.Core.TyCo.FVs.isInjectiveInType` as a more efficient
  way to find if a particular type variable is used injectively than
  finding all the injective variables.  It is called in
  `GHC.Tc.Utils.Unify.definitely_poly`, which in turn is used quite a
  lot.

* Moved `rewriterView` to `GHC.Core.Type`, so we can use it from the
  constraint solver.

Fixes #22194, #23199

Compile times decrease by an average of 0.1%; but there is a 7.4%
drop in compiler allocation on T15703.

Metric Decrease:
    T15703

Haskell-mouse authored 1 year ago and Marge Bot committed 1 year ago

I've turned all occurrences of TcRnUnknownMessage in GHC.Rename.HsType
module into a proper TcRnMessage.
Instead, these TcRnMessage messages were introduced:

TcRnDataKindsError
TcRnUnusedQuantifiedTypeVar
TcRnIllegalKindSignature
TcRnUnexpectedPatSigType
TcRnSectionPrecedenceError
TcRnPrecedenceParsingError
TcRnIllegalKind
TcRnNegativeNumTypeLiteral
TcRnUnexpectedKindVar
TcRnBindMultipleVariables
TcRnBindVarAlreadyInScope

Torsten Schmits authored 2 years ago and Marge Bot committed 1 year ago

Tracking ticket: #20117

MR: !10183

This converts uses of `mkTcRnUnknownMessage` to newly added constructors
of `TcRnMessage`.

Torsten Schmits authored 2 years ago and Marge Bot committed 2 years ago

Tracking ticket: #20119

MR: !10138

This converts uses of `mkTcRnUnknownMessage` to newly added constructors
of `TcRnMessage`.

Andrei Borzenkov authored 2 years ago and Marge Bot committed 2 years ago

I've turned almost all occurrences of TcRnUnknownMessage in GHC.Rename.Module
module into a proper TcRnMessage.
Instead, these TcRnMessage messages were introduced:
  TcRnIllegalInstanceHeadDecl
  TcRnUnexpectedStandaloneDerivingDecl
  TcRnUnusedVariableInRuleDecl
  TcRnUnexpectedStandaloneKindSig
  TcRnIllegalRuleLhs
  TcRnBadAssocRhs
  TcRnDuplicateRoleAnnot
  TcRnDuplicateKindSig
  TcRnIllegalDerivStrategy
  TcRnIllegalMultipleDerivClauses
  TcRnNoDerivStratSpecified
  TcRnStupidThetaInGadt
  TcRnBadImplicitSplice
  TcRnShadowedTyVarNameInFamResult
  TcRnIncorrectTyVarOnLhsOfInjCond
  TcRnUnknownTyVarsOnRhsOfInjCond

Was introduced one helper type:
  RuleLhsErrReason

Simon Peyton Jones authored 2 years ago and Marge Bot committed 2 years ago

runtimeRepLevity_maybe was panicing unnecessarily; and
the error printing code made use of the case when it should
return Nothing rather than panicing.

For some bizarre reason perf/compiler/T21839r shows a 10% bump in runtime
peak-megagbytes-used, on a single architecture (alpine). See !9753 for
commentary, but I'm going to accept it.

Metric Increase:
    T21839r

Simon Peyton Jones authored 2 years ago and Marge Bot committed 2 years ago

Ticket #22743 pointed out that there is a missing check,
for type-inferred bindings, that the inferred type doesn't
have an escaping kind.

The fix is easy.

Richard Eisenberg authored 2 years ago and Matthew Pickering committed 2 years ago

This implements proposal 547 and closes ticket #22298.
See the proposal and ticket for motivation.

Compiler perf improves a bit

Metrics: compile_time/bytes allocated
-------------------------------------
  CoOpt_Singletons(normal)   -2.4% GOOD
            T12545(normal)   +1.0%
            T13035(normal)  -13.5% GOOD
            T18478(normal)   +0.9%
            T9872d(normal)   -2.2% GOOD

                 geo. mean   -0.2%
                 minimum    -13.5%
                 maximum     +1.0%

Metric Decrease:
    CoOpt_Singletons
    T13035
    T9872d

Apoorv Ingle authored 2 years ago and Marge Bot committed 2 years ago

Fixes: #217093
Associated to #19415

This change
* Flips the orientation of the the generated kind equality coercion in canEqLHSHetero;
* Removes `cc_fundeps` in CDictCan as the check was incomplete;
* Changes `canDecomposableTyConAppOk` to ensure we process kind equalities before type equalities and avoiding a call to `canEqLHSHetero` while processing wanted TyConApp equalities
* Adds 2 new tests for validating the change
   - testsuites/typecheck/should_compile/T21703.hs and
   - testsuites/typecheck/should_fail/T19415b.hs (a simpler version of T19415.hs)
* Misc: Due to the change in the equality direction some error messages now have flipped type mismatch errors
* Changes in Notes:
  - Note [Fundeps with instances, and equality orientation] supercedes Note [Fundeps with instances]
  - Added Note [Kind Equality Orientation] to visualize the kind flipping
  - Added Note [Decomposing Dependent TyCons and Processing Wanted Equalties]

Vladislav Zavialov authored 2 years ago and Marge Bot committed 2 years ago

Before this patch, GHC unconditionally printed ticks before promoted
data constructors:

	ghci> type T = True  -- unticked (user-written)
	ghci> :kind! T
	T :: Bool
	= 'True              -- ticked (compiler output)

After this patch, GHC prints ticks only when necessary:

	ghci> type F = False    -- unticked (user-written)
	ghci> :kind! F
	F :: Bool
	= False                 -- unticked (compiler output)

	ghci> data False        -- introduce ambiguity
	ghci> :kind! F
	F :: Bool
	= 'False                -- ticked by necessity (compiler output)

The old behavior can be enabled by -fprint-redundant-promotion-ticks.

Summary of changes:
* Rename PrintUnqualified to NamePprCtx
* Add QueryPromotionTick to it
* Consult the GlobalRdrEnv to decide whether to print a tick (see mkPromTick)
* Introduce -fprint-redundant-promotion-ticks

Co-authored-by: Artyom Kuznetsov <hi@wzrd.ht>

Simon Peyton Jones authored 2 years ago and Simon Peyton Jones committed 2 years ago

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

Simon Peyton Jones authored 2 years ago and Marge Bot committed 2 years ago

Ticket #22379 revealed that skolemiseQuantifiedTyVar was
dropping the passed-in skol_info on the floor when it encountered
a SkolemTv.  Bad!  Several TyCons thereby share a single SkolemInfo
on their binders, which lead to bogus error reports.

Necessary for newer cross-compiling backends (JS, Wasm) that don't
support TH yet.

Finley McIlwaine authored 2 years ago and Marge Bot committed 2 years ago

When a newtype introduces GADT eq_specs due to a defaulted
RuntimeRep, we detect this and print the error message with
explicit kinds.

This also refactors newtype type checking to use the new
diagnostic infra.

Fixes #21447

sheaf authored 2 years ago and Marge Bot committed 2 years ago

The testsuite output now contains diagnostic codes, so many tests need
to be updated at once.
We decided it was best to keep the diagnostic codes in the testsuite
output, so that contributors don't inadvertently make changes to the
diagnostic codes.

Soham Chowdhury authored 2 years ago and Marge Bot committed 2 years ago

This patch improves the uniformity of error message formatting by
printing constraints in quotes, as we do for types.

Fix #21167

Ben Gamari authored 2 years ago and Marge Bot committed 2 years ago

Previously several tests' output were unnecessarily dependent on version
numbers, particularly of `base`. Fix this.

Ben Gamari authored 2 years ago and Marge Bot committed 2 years ago

To 0.9.0 and 4.17.0 respectively.

Bumps array, deepseq, directory, filepath, haskeline, hpc, parsec, stm,
terminfo, text, unix, haddock, and hsc2hs submodules.

(cherry picked from commit ba47b951)

HaskellMouse authored 2 years ago and Marge Bot committed 2 years ago

This commit fixes #20312
It deprecates "TypeInType" extension
according to the following proposal:
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0083-no-type-in-type.rst

It has been already implemented.

The migration strategy:
 1. Disable TypeInType
 2. Enable both DataKinds and PolyKinds extensions

Metric Decrease:
    T16875

Krzysztof Gogolewski authored 2 years ago and Matthew Pickering committed 2 years ago

Users are supposed to import GHC.Exts rather than GHC.Prim.
Part of #18749.

* Users can define their own (~) type operator
* Haddock can display documentation for the built-in (~)
* New transitional warnings implemented:
    -Wtype-equality-out-of-scope
    -Wtype-equality-requires-operators

Updates the haddock submodule.

Richard Eisenberg authored 3 years ago and Marge Bot committed 3 years ago

Co-authored by: Sam Derbyshire

Previously, GHC had three flavours of constraint:
Wanted, Given, and Derived. This removes Derived constraints.

Though serving a number of purposes, the most important role
of Derived constraints was to enable better error messages.
This job has been taken over by the new RewriterSets, as explained
in Note [Wanteds rewrite wanteds] in GHC.Tc.Types.Constraint.

Other knock-on effects:
 - Various new Notes as I learned about under-described bits of GHC

 - A reshuffling around the AST for implicit-parameter bindings,
   with better integration with TTG.

 - Various improvements around fundeps. These were caused by the
   fact that, previously, fundep constraints were all Derived,
   and Derived constraints would get dropped. Thus, an unsolved
   Derived didn't stop compilation. Without Derived, this is no
   longer possible, and so we have to be considerably more careful
   around fundeps.

 - A nice little refactoring in GHC.Tc.Errors to center the work
   on a new datatype called ErrorItem. Constraints are converted
   into ErrorItems at the start of processing, and this allows for
   a little preprocessing before the main classification.

 - This commit also cleans up the behavior in generalisation around
   functional dependencies. Now, if a variable is determined by
   functional dependencies, it will not be quantified. This change
   is user facing, but it should trim down GHC's strange behavior
   around fundeps.

 - Previously, reportWanteds did quite a bit of work, even on an empty
   WantedConstraints. This commit adds a fast path.

 - Now, GHC will unconditionally re-simplify constraints during
   quantification. See Note [Unconditionally resimplify constraints when
   quantifying], in GHC.Tc.Solver.

Close #18398.
Close #18406.
Solve the fundep-related non-confluence in #18851.
Close #19131.
Close #19137.
Close #20922.
Close #20668.
Close #19665.

-------------------------
Metric Decrease:
    LargeRecord
    T9872b
    T9872b_defer
    T9872d
    TcPlugin_RewritePerf
-------------------------

Matthew Pickering authored 3 years ago and Marge Bot committed 3 years ago

Note [Tidying multiple names at once] indicates that if multiple
variables have the same name then we shouldn't prioritise one of them
and instead rename them all to a1, a2, a3... etc

This patch implements that change, some error message changes as
expected.

Closes #20932

Matthew Pickering authored 3 years ago and Marge Bot committed 3 years ago

The main purpose of this patch is to attach a SkolemInfo directly to
each SkolemTv. This fixes the large number of bugs which have
accumulated over the years where we failed to report errors due to
having "no skolem info" for particular type variables. Now the origin of
each type varible is stored on the type variable we can always report
accurately where it cames from.

Fixes #20969 #20732 #20680 #19482 #20232 #19752 #10946
  #19760 #20063 #13499 #14040

The main changes of this patch are:

* SkolemTv now contains a SkolemInfo field which tells us how the
  SkolemTv was created. Used when reporting errors.

* Enforce invariants relating the SkolemInfoAnon and level of an implication (ic_info, ic_tclvl)
  to the SkolemInfo and level of the type variables in ic_skols.
    * All ic_skols are TcTyVars -- Check is currently disabled
    * All ic_skols are SkolemTv
    * The tv_lvl of the ic_skols agrees with the ic_tclvl
    * The ic_info agrees with the SkolInfo of the implication.

  These invariants are checked by a debug compiler by
  checkImplicationInvariants.

* Completely refactor kcCheckDeclHeader_sig which kept
  doing my head in. Plus, it wasn't right because it wasn't skolemising
  the binders as it decomposed the kind signature.

  The new story is described in Note [kcCheckDeclHeader_sig].  The code
  is considerably shorter than before (roughly 240 lines turns into 150
  lines).

  It still has the same awkward complexity around computing arity as
  before, but that is a language design issue.
  See Note [Arity inference in kcCheckDeclHeader_sig]

* I added new type synonyms MonoTcTyCon and PolyTcTyCon, and used
  them to be clear which TcTyCons have "finished" kinds etc, and
  which are monomorphic. See Note [TcTyCon, MonoTcTyCon, and PolyTcTyCon]

* I renamed etaExpandAlgTyCon to splitTyConKind, becuase that's a
  better name, and it is very useful in kcCheckDeclHeader_sig, where
  eta-expansion isn't an issue.

* Kill off the nasty `ClassScopedTvEnv` entirely.

Co-authored-by: Simon Peyton Jones <simon.peytonjones@gmail.com>

sheaf authored 3 years ago and Marge Bot committed 3 years ago

  When instances overlap, we now include additional information
  about why we weren't able to select an instance: perhaps
  one instance overlapped another but was not strictly more specific,
  so we aren't able to directly choose it.

Fixes #20542

sheaf authored 3 years ago and Marge Bot committed 3 years ago

PHASE 1: we never rewrite Concrete# evidence.

This patch migrates all the representation polymorphism checks to
the typechecker, using a new constraint form

  Concrete# :: forall k. k -> TupleRep '[]

Whenever a type `ty` must be representation-polymorphic
(e.g. it is the type of an argument to a function), we emit a new
`Concrete# ty` Wanted constraint. If this constraint goes
unsolved, we report a representation-polymorphism error to the user.
The 'FRROrigin' datatype keeps track of the context of the
representation-polymorphism check, for more informative error messages.

This paves the way for further improvements, such as
allowing type families in RuntimeReps and improving the soundness
of typed Template Haskell. This is left as future work (PHASE 2).

fixes #17907 #20277 #20330 #20423 #20426

updates haddock submodule

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Metric Decrease:
    T5642
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sheaf authored 3 years ago and Marge Bot committed 3 years ago

There were two problems around `mkDictErr`:

  1. An outdated call to `flattenTys` meant that we missed out on some
     instances. As we no longer flatten type-family applications,
     the logic is obsolete and can be removed.

  2. We reported "out of scope" errors in a poly-kinded situation
     because `BoxedRep` and `Lifted` were considered out of scope.
     We fix this by using `pretendNameIsInScope`.

fixes #20465

- Add 19 new messages. Update test outputs accordingly.

- Pretty print suggest-extensions hints: remove space before
interspersed commas.

- Refactor Rank's MonoType constructors. Each MonoType constructor
should represent a specific case. With the Doc suggestion belonging
to the TcRnMessage diagnostics instead.

- Move Rank from Validity to its own `GHC.Tc.Types.Rank` module.

- Remove the outdated `check_irred_pred` check.

- Remove the outdated duplication check in `check_valid_theta`, which
was subsumed by `redundant-constraints`.

- Add missing test cases for quantified-constraints/T16474 & th/T12387a.

sheaf authored 3 years ago and Marge Bot committed 3 years ago

fixes #19756, updates haddock submodule

Matthew Pickering authored 3 years ago and Marge Bot committed 3 years ago

This commit modifies interface files so that *only* direct information
about modules and packages is stored in the interface file.

* Only direct module and direct package dependencies are stored in the
interface files.
* Trusted packages are now stored separately as they need to be checked
  transitively.
* hs-boot files below the compiled module in the home module are stored
  so that eps_is_boot can be calculated in one-shot mode without loading
  all interface files in the home package.
* The transitive closure of signatures is stored separately

This is important for two reasons

* Less recompilation is needed, as motivated by #16885, a lot of
redundant compilation was triggered when adding new imports deep in the
module tree as all the parent interface files had to be redundantly
updated.
* Checking an interface file is cheaper because you don't have to
perform a transitive traversal to check the dependencies are up-to-date.

In the code, places where we would have used the transitive closure, we
instead compute the necessary transitive closure. The closure is not
computed very often, was already happening in checkDependencies, and
was already happening in getLinkDeps.

Fixes #16885

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Metric Decrease:
    MultiLayerModules
    T13701
    T13719
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