[Git][ghc/ghc][wip/T22194-flags] 18 commits: Add release note for GHC.Unicode refactor in base-4.18.

Simon Peyton Jones (@simonpj) gitlab at gitlab.haskell.org
Thu Apr 13 09:27:26 UTC 2023 


Simon Peyton Jones pushed to branch wip/T22194-flags at Glasgow Haskell Compiler / GHC


Commits:
0c990e13 by Pierre Le Marre at 2023-04-06T10:16:29+00:00
Add release note for GHC.Unicode refactor in base-4.18.

Also merge CLC proposal 130 in base-4.19 with CLC proposal 59 in
base-4.18 and add proper release date.

- - - - -
cbbfb283 by Alex Dixon at 2023-04-07T18:27:45-04:00
Improve documentation for ($) (#22963)

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5193c2b0 by Alex Dixon at 2023-04-07T18:27:45-04:00
Remove trailing whitespace from ($) commentary

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b384523b by Sebastian Graf at 2023-04-07T18:27:45-04:00
Adjust wording wrt representation polymorphism of ($)
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6a788f0a by Torsten Schmits at 2023-04-07T22:29:28-04:00
Add structured error messages for GHC.Tc.TyCl.Utils

Tracking ticket: #20117

MR: !10251

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

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3ba77b36 by sheaf at 2023-04-07T22:30:07-04:00
Renamer: don't call addUsedGRE on an exact Name

When looking up a record field in GHC.Rename.Env.lookupRecFieldOcc,
we could end up calling addUsedGRE on an exact Name, which would then
lead to a panic in the bestImport function: it would be incapable of
processing a GRE which is not local but also not brought into scope
by any imports (as it is referred to by its unique instead).

Fixes #23240

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bc4795d2 by Krzysztof Gogolewski at 2023-04-11T19:24:54-04:00
Add support for -debug in the testsuite

Confusingly, GhcDebugged referred to GhcDebugAssertions.

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b7474b57 by Krzysztof Gogolewski at 2023-04-11T19:24:54-04:00
Add missing cases in -Di prettyprinter

Fixes #23142

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6c392616 by Cheng Shao at 2023-04-11T19:25:31-04:00
compiler: make WasmCodeGenM an instance of MonadUnique

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05d26a65 by Cheng Shao at 2023-04-11T19:25:31-04:00
compiler: apply cmm node-splitting for wasm backend

This patch applies cmm node-splitting for wasm32 NCG, which is
required when handling irreducible CFGs. Fixes #23237.

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f1892cc0 by Bodigrim at 2023-04-11T19:26:09-04:00
Set base 'maintainer' field to CLC

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ecf22da3 by Simon Peyton Jones at 2023-04-11T19:26:45-04:00
Clarify a couple of Notes about 'nospec'

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ebd8918b by Oleg Grenrus at 2023-04-12T12:32:57-04:00
Allow generation of TTH syntax with TH

In other words allow generation of typed splices and brackets with
Untyped Template Haskell.

That is useful in cases where a library is build with TTH in mind,
but we still want to generate some auxiliary declarations,
where TTH cannot help us, but untyped TH can.
Such example is e.g. `staged-sop` which works with TTH,
but we would like to derive `Generic` declarations with TH.

An alternative approach is to use `unsafeCodeCoerce`, but then the
derived `Generic` instances would be type-checked only at use sites,
i.e. much later. Also `-ddump-splices` output is quite ugly:
user-written instances would use TTH brackets, not `unsafeCodeCoerce`.

This commit doesn't allow generating of untyped template splices
and brackets with untyped TH, as I don't know why one would want to do
that (instead of merging the splices, e.g.)

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690d0225 by Rodrigo Mesquita at 2023-04-12T12:33:33-04:00
Add regression test for #23229

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5c16501f by Simon Peyton Jones at 2023-04-13T10:29:12+01:00
Major refactor in the handling of equality constraints

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

- - - - -
b431140c by Simon Peyton Jones at 2023-04-13T10:29:12+01:00
Add some documentation about redundant constraints

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9fcad479 by Simon Peyton Jones at 2023-04-13T10:29:12+01:00
Improve partial signatures

This MR fixes #23223. The changes are in two places:

* GHC.Tc.Bind.checkMonomorphismRestriction
  See the new `Note [When the MR applies]`
  We now no longer stupidly attempt to apply the MR when the user
  specifies a context, e.g.   f :: Eq a => _ -> _

* GHC.Tc.Solver.decideQuantification
  See rewritten `Note [Constraints in partial type signatures]`

Fixing this bug apparently breaks three tests:

* partial-sigs/should_compile/T11192
* partial-sigs/should_fail/Defaulting1MROff
* partial-sigs/should_fail/T11122

However they are all symptoms of #23232, so I'm marking them as
expect_broken(23232).

I feel happy about this MR. Nice.

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e7ea954b by Simon Peyton Jones at 2023-04-13T10:29:12+01:00
Make approximateWC a bit cleverer

This MR fixes #23224: making approximateWC more clever

See the long `Note [ApproximateWC]` in GHC.Tc.Solver

All this is delicate and ad-hoc -- but it /has/ to be: we are
talking about inferring a type for a binding in the presence of
GADTs, type families and whatnot: known difficult territory.
We just try as hard as we can.

- - - - -


23 changed files:

- compiler/GHC/CmmToAsm/Wasm/FromCmm.hs
- compiler/GHC/CmmToAsm/Wasm/Types.hs
- compiler/GHC/Core/InstEnv.hs
- compiler/GHC/Core/Opt/Simplify/Iteration.hs
- compiler/GHC/Core/TyCo/FVs.hs
- compiler/GHC/Core/TyCo/Rep.hs
- compiler/GHC/Core/TyCon.hs
- compiler/GHC/Core/Type.hs
- compiler/GHC/Core/Type.hs-boot
- compiler/GHC/Data/Bag.hs
- compiler/GHC/Data/Maybe.hs
- compiler/GHC/Hs/Expr.hs
- compiler/GHC/Rename/Env.hs
- compiler/GHC/Rename/Names.hs
- compiler/GHC/Tc/Errors.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Tc/Gen/Bind.hs
- compiler/GHC/Tc/Gen/Sig.hs
- compiler/GHC/Tc/Solver.hs
- compiler/GHC/Tc/Solver/Equality.hs
- compiler/GHC/Tc/Solver/InertSet.hs
- compiler/GHC/Tc/Solver/Monad.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/7d6284dacc3bf215bfe55006e830583b0d163074...e7ea954b8ad6beac0c6f3eb350f0b576d42b3e68

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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/7d6284dacc3bf215bfe55006e830583b0d163074...e7ea954b8ad6beac0c6f3eb350f0b576d42b3e68
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