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Bodigrim pushed to branch wip/warning-for-last-and-init at Glasgow Haskell Compiler / GHC

Commits:

19f20861

by Simon Peyton Jones at 2025-06-13T09:51:11-04:00

Improve redundant constraints for instance decls

Addresses #25992, which showed that the default methods
of an instance decl could make GHC fail to report redundant
constraints.

Figuring out how to do this led me to refactor the computation
of redundant constraints.  See the entirely rewritten

   Note [Tracking redundant constraints]

in GHC.Tc.Solver.Solve

1d02798e

by Matthew Pickering at 2025-06-13T09:51:54-04:00

Refactor the treatment of nested Template Haskell splices

* The difference between a normal splice, a quasiquoter and implicit
splice caused by lifting is stored in the AST after renaming.

* Information that the renamer learns about splices is stored in the
relevant splice extension points (XUntypedSpliceExpr, XQuasiQuote).

* Normal splices and quasi quotes record the flavour of splice
  (exp/pat/dec etc)

* Implicit lifting stores information about why the lift was attempted,
  so if it fails, that can be reported to the user.

* After renaming, the decision taken to attempt to implicitly lift a
variable is stored in the `XXUntypedSplice` extension field in the
`HsImplicitLiftSplice` constructor.

* Since all the information is stored in the AST, in `HsUntypedSplice`,
  the type of `PendingRnSplice` now just stores a `HsUntypedSplice`.

* Error messages since the original program can be easily
  printed, this is noticeable in the case of implicit lifting.
* The user-written syntax is directly type-checked. Before, some
  desugaring took place in the
* Fixes .hie files to work better with nested splices (nested splices
  are not indexed)
* The location of the quoter in a quasiquote is now located, so error
  messages will precisely point to it (and again, it is indexed by hie
  files)

In the future, the typechecked AST should also retain information about
the splices and the specific desugaring being left to the desugarer.

Also, `runRnSplice` should call `tcUntypedSplice`, otherwise the
typechecking logic is duplicated (see the `QQError` and `QQTopError`
tests for a difference caused by this).

f93798ba

by Cheng Shao at 2025-06-13T09:52:35-04:00

libffi: update to 3.5.1

Bumps libffi submodule.

c7aa0c10

by Andreas Klebinger at 2025-06-15T05:47:24-04:00

Revert "Specialise: Don't float out constraint components."

This reverts commit c9abb87ccc0c91cd94f42b3e36270158398326ef.

Turns out two benchmarks from #19747 regresses by a factor of 7-8x if
we do not float those out.

fd998679

by Krzysztof Gogolewski at 2025-06-15T05:48:06-04:00

Fix EPT enforcement when mixing unboxed tuples and non-tuples

The code was assuming that an alternative cannot be returning a normal
datacon and an unboxed tuple at the same time. However, as seen in #26107,
this can happen when using a GADT to refine the representation type.

The solution is just to conservatively return TagDunno.

e64b3f16

by ARATA Mizuki at 2025-06-17T10:13:42+09:00

MachRegs.h: Don't define NO_ARG_REGS when a XMM register is defined

On i386, MAX_REAL_VANILLA_REG is 1, but MAX_REAL_XMM_REG is 4.
If we define NO_ARG_REGS on i386, programs that use SIMD vectors may segfault.

Closes #25985

A couple of notes on the BROKEN_TESTS field:

* This fixes the segfault from T25062_V16.
* The failure from T22187_run was fixed in an earlier commit (see #25561),
  but BROKEN_TESTS was missed at that time.  Now should be a good time to
  mark it fixed.

3e7c6b4d

by Matthew Pickering at 2025-06-18T15:34:04-04:00

Improve error messages when implicit lifting fails

This patch concerns programs which automatically try to fix level errors
by inserting `Lift`. For example:

```
foo x = [| x |]
~>
foo x = [| $(lift x) |]
```

Before, there were two problems with the message.

1. (#26031), the location of the error was reported as the whole
   quotation.
2. (#26035), the message just mentions there is no Lift instance, but
   gives no indicate why the user program needed a Lift instance in the
   first place.

This problem is especially bad when you disable
`ImplicitStagePersistence`, so you just end up with a confusing "No
instance for" message rather than an error message about levels

This patch fixes both these issues.

Firstly, `PendingRnSplice` differentiates between a user-written splice
and an implicit lift. Then, the Lift instance is precisely requested
with a specific origin in the typechecker. If the instance fails to be
solved, the message is reported using the `TcRnBadlyLevelled`
constructor (like a normal level error).

Fixes #26031, #26035

44b8cee2
by Cheng Shao at 2025-06-18T15:34:46-04:00
```
testsuite: add T26120 marked as broken
```

894a04f3

by Cheng Shao at 2025-06-18T15:34:46-04:00

compiler: fix GHC.SysTools.Ar archive member size writing logic

This patch fixes a long-standing bug in `GHC.SysTools.Ar` that emits
the wrong archive member size in each archive header. It should encode
the exact length of the member payload, excluding any padding byte,
otherwise malformed archive that extracts a broken object with an
extra trailing byte could be created.

Apart from the in-tree `T26120` test, I've also created an out-of-tree
testsuite at https://github.com/TerrorJack/ghc-ar-quickcheck that
contains QuickCheck roundtrip tests for `GHC.SysTools.Ar`. With this
fix, simple roundtrip tests and `writeGNUAr`/GNU `ar` roundtrip test
passes. There might be more bugs lurking in here, but this patch is
still a critical bugfix already.

Fixes #26120 #22586.

Co-authored-by: Codex <codex@openai.com>

f677ab5f

by Lauren Yim at 2025-06-18T15:35:37-04:00

fix some typos in the warnings page in the user guide

b968e1c1

by Rodrigo Mesquita at 2025-06-18T15:36:18-04:00

Add a frozen callstack to throwGhcException

Fixes #25956

a5e0c3a3

by fendor at 2025-06-18T15:36:59-04:00

Update using.rst to advertise full mhu support for GHCi

d3e60e97

by Ryan Scott at 2025-06-18T22:29:21-04:00

Deprecate -Wdata-kinds-tc, make DataKinds issues in typechecker become errors

!11314 introduced the `-Wdata-kinds-tc` warning as part of a fix for #22141.
This was a temporary stopgap measure to allow users who were accidentally
relying on code which needed the `DataKinds` extension in order to typecheck
without having to explicitly enable the extension.

Now that some amount of time has passed, this patch deprecates
`-Wdata-kinds-tc` and upgrades any `DataKinds`-related issues in the
typechecker (which were previously warnings) into errors.

fd5b5177

by Ryan Hendrickson at 2025-06-18T22:30:06-04:00

haddock: Add redact-type-synonyms pragma

`{-# OPTIONS_HADDOCK redact-type-synonyms #-}` pragma will hide the RHS
of type synonyms, and display the result kind instead, if the RHS
contains any unexported types.

fbc0b92a

by Vladislav Zavialov at 2025-06-22T04:25:16+03:00

Visible forall in GADTs (#25127)

Add support for visible dependent quantification `forall a -> t` in
types of data constructors, e.g.

  data KindVal a where
    K :: forall k.
         forall (a::k) ->   -- now allowed!
         k ->
         KindVal a

For details, see docs/users_guide/exts/required_type_arguments.rst,
which has gained a new subsection.

DataCon in compiler/GHC/Core/DataCon.hs
---------------------------------------
The main change in this patch is that DataCon, the Core representation
of a data constructor, now uses a different type to store user-written
type variable binders:

  - dcUserTyVarBinders :: [InvisTVBinder]
  + dcUserTyVarBinders :: [TyVarBinder]

where

  type TyVarBinder   = VarBndr TyVar ForAllTyFlag
  type InvisTVBinder = VarBndr TyVar Specificity

and

  data Specificity  = InferredSpec | SpecifiedSpec
  data ForAllTyFlag = Invisible Specificity | Required

This change necessitates some boring, mechanical changes scattered
throughout the diff:

    ... is now used in place of ...
   -----------------+---------------
    TyVarBinder     | InvisTVBinder
    IfaceForAllBndr | IfaceForAllSpecBndr
    Specified       | SpecifiedSpec
    Inferred        | InferredSpec
    mkForAllTys     | mkInvisForAllTys

  additionally,

    tyVarSpecToBinders      -- added or removed calls
    ifaceForAllSpecToBndrs  -- removed calls

Visibility casts in mkDataConRep
--------------------------------
Type abstractions in Core (/\a. e) always have type (forall a. t)
because coreTyLamForAllTyFlag = Specified. This is also true of data
constructor workers. So we may be faced with the following:

  data con worker:  (forall a.   blah)
  data con wrapper: (forall a -> blah)

In this case the wrapper must use a visibility cast (e |> ForAllCo ...)
with appropriately set fco_vis{L,R}. Relevant functions:

  mkDataConRep   in compiler/GHC/Types/Id/Make.hs
  dataConUserTyVarBindersNeedWrapper in compiler/GHC/Core/DataCon.hs
  mkForAllVisCos in compiler/GHC/Core/Coercion.hs
  mkCoreTyLams   in compiler/GHC/Core/Make.hs
  mkWpForAllCast in compiler/GHC/Tc/Types/Evidence.hs

More specifically:

- dataConUserTyVarBindersNeedWrapper has been updated to answer "yes"
  if there are visible foralls in the type of the data constructor.

- mkDataConRep now uses mkCoreTyLams to generate the big lambda
  abstractions (/\a b c. e) in the data con wrapper.

- mkCoreTyLams is a variant of mkCoreLams that applies visibility casts
  as needed. It similar in purpose to the pre-existing mkWpForAllCast,
  so the common bits have been factored out into mkForAllVisCos.

ConDecl in compiler/Language/Haskell/Syntax/Decls.hs
----------------------------------------------------
The surface syntax representation of a data constructor declaration is
ConDecl. In accordance with the proposal, only GADT syntax is extended
with support for visible forall, so we are interested in ConDeclGADT.

ConDeclGADT's field con_bndrs has been renamed to con_outer_bndrs
and is now accompanied by con_inner_bndrs:

  con_outer_bndrs :: XRec pass (HsOuterSigTyVarBndrs pass)
  con_inner_bndrs :: [HsForAllTelescope pass]

Visible foralls always end up in con_inner_bndrs. The outer binders are
stored and processed separately to support implicit quantification and
the forall-or-nothing rule, a design established by HsSigType.

A side effect of this change is that even in absence of visible foralls,
GHC now permits multiple invisible foralls, e.g.

  data T a where { MkT :: forall a b. forall c d. ... -> T a }

But of course, this is done in service of making at least some of these
foralls visible. The entire compiler front-end has been updated to deal
with con_inner_bndrs. See the following modified or added functions:

  Parser:
      mkGadtDecl     in compiler/GHC/Parser/PostProcess.hs
      splitLHsGadtTy in compiler/GHC/Hs/Type.hs
  Pretty-printer:
      pprConDecl           in compiler/GHC/Hs/Decls.hs
      pprHsForAllTelescope in compiler/GHC/Hs/Type.hs
  Renamer:
      rnConDecl                 in compiler/GHC/Rename/Module.hs
      bindHsForAllTelescopes    in compiler/GHC/Rename/HsType.hs
      extractHsForAllTelescopes in compiler/GHC/Rename/HsType.hs
  Type checker:
      tcConDecl           in compiler/GHC/Tc/TyCl.hs
      tcGadtConTyVarBndrs in compiler/GHC/Tc/Gen/HsType.hs

Template Haskell
----------------
The TH AST is left unchanged for the moment to avoid breakage. An
attempt to quote or reify a data constructor declaration with visible
forall in its type will result an error:

  data ThRejectionReason       -- in GHC/HsToCore/Errors/Types.hs
    = ...
    | ThDataConVisibleForall   -- new error constructor

However, as noted in the previous section, GHC now permits multiple
invisible foralls, and TH was updated accordingly. Updated code:

      repC         in compiler/GHC/HsToCore/Quote.hs
      reifyDataCon in compiler/GHC/Tc/Gen/Splice.hs
      ppr @Con     in libraries/ghc-boot-th/GHC/Boot/TH/Ppr.hs

Pattern matching
----------------
Everything described above concerns data constructor declarations, but
what about their use sites? Now it is trickier to type check a pattern
match fn(Con a b c)=... because we can no longer assume that a,b,c are
all value arguments. Indeed, some or all of them may very well turn out
to be required type arguments.

To that end, see the changes to:

      tcDataConPat   in compiler/GHC/Tc/Gen/Pat.hs
      splitConTyArgs in compiler/GHC/Tc/Gen/Pat.hs

and the new helpers split_con_ty_args, zip_pats_bndrs.

This is also the reason the TcRnTooManyTyArgsInConPattern error
constructor has been removed. The new code emits TcRnArityMismatch
or TcRnIllegalInvisibleTypePattern.

Summary
-------
DataCon, ConDecl, as well as all related functions have been updated to
support required type arguments in data constructors.

Test cases:
  HieGadtConSigs   GadtConSigs_th_dump1   GadtConSigs_th_pprint1
  T25127_data      T25127_data_inst       T25127_infix
  T25127_newtype   T25127_fail_th_quote   T25127_fail_arity
  TyAppPat_Tricky

Co-authored-by: mniip <mniip@mniip.com>

ae003a3a

by Teo Camarasu at 2025-06-23T05:21:48-04:00

linters: lint-whitespace: bump upper-bound for containers

The version of containers was bumped in https://gitlab.haskell.org/ghc/ghc/-/merge_requests/13989

0fb37893

by Matthew Pickering at 2025-06-23T13:55:10-04:00

Move ModuleGraph into UnitEnv

The ModuleGraph is a piece of information associated with the
ExternalPackageState and HomeUnitGraph. Therefore we should store it
inside the HomeUnitEnv.

3bf6720e

by soulomoon at 2025-06-23T13:55:52-04:00

Remove hptAllFamInstances usage during upsweep

Fixes #26118

This change eliminates the use of hptAllFamInstances during the upsweep phase,
as it could access non-below modules from the home package table.

The following updates were made:

* Updated checkFamInstConsistency to accept an explicit ModuleEnv FamInstEnv
  parameter and removed the call to hptAllFamInstances.
* Adjusted hugInstancesBelow so we can construct ModuleEnv FamInstEnv
  from its result,
* hptAllFamInstances and allFamInstances functions are removed.

83ee7b78

by Ben Gamari at 2025-06-24T05:02:07-04:00

configure: Don't force value of OTOOL, etc. if not present

Previously if `otool` and `install_name_tool` were not present they
would be overridden by `fp_settings.m4`. This logic was introduced in
4ff93292243888545da452ea4d4c1987f2343591 without explanation.

9329c9e1

by Ben Gamari at 2025-06-24T05:02:07-04:00

ghc-toolchain: Add support for otool, install_name_tool

Fixes part of ghc#23675.

25f5c998

by Ben Gamari at 2025-06-24T05:02:08-04:00

ghc-toolchain: Add support for llc, opt, llvm-as

Fixes #23675.

51d150dd

by Rodrigo Mesquita at 2025-06-24T05:02:08-04:00

hadrian: Use settings-use-distro-mingw directly

The type `ToolchainSetting` only made sense when we had more settings to
fetch from the system config file. Even then "settings-use-distro-mingw"
is arguably not a toolchain setting.

With the fix for #23675, all toolchain tools were moved to the
`ghc-toolchain` `Toolchain` format. Therefore, we can inline
`settings-use-distro-mingw` accesses and delete `ToolchainSetting`.

dcf68a83

by Rodrigo Mesquita at 2025-06-24T05:02:08-04:00

configure: Check LlvmTarget exists for LlvmAsFlags

If LlvmTarget was empty, LlvmAsFlags would be just "--target=".
If it is empty now, simply keep LlvmAsFlags empty.

ghc-toolchain already does this right. This fix makes the two
configurations match up.

580a3353

by Ben Gamari at 2025-06-24T05:02:51-04:00

rts/linker/LoadArchive: Use bool

Improve type precision by using `bool` instead of `int` and `StgBool`.

76d1041d

by Ben Gamari at 2025-06-24T05:02:51-04:00

rts/linker/LoadArchive: Don't rely on file extensions for identification

Previously archive members would be identified via their file extension,
as described in #13103. We now instead use a more principled approach,
relying on the magic number in the member's header.

As well, we refactor treatment of archive format detection to improve
code clarity and error handling.

Closes #13103.

4b748a99

by Teo Camarasu at 2025-06-24T15:31:07-04:00

template-haskell: improve changelog


stable -> more stable, just to clarify that this interface isn't fully stable.

errornously -> mistakenly: I typod this and also let's go for a simpler word

e358e477
by Sylvain Henry at 2025-06-24T15:31:58-04:00
```
Bump stack resolver to use GHC 9.6.7

Cf #26139
```

4bf5eb63

by fendor at 2025-06-25T17:05:43-04:00

Teach `:reload` about multiple home units

`:reload` needs to lookup the `ModuleName` and must not assume the given
`ModuleName` is in the current `HomeUnit`.

We add a new utility function which allows us to find a `HomeUnitModule`
instead of a `Module`.

Further, we introduce the `GhciCommandError` type which can be used to
abort the execution of a GHCi command.
This error is caught and printed in a human readable fashion.

b3d97bb3

by fendor at 2025-06-25T17:06:25-04:00

Implement `-fno-load-initial-targets` flag

We add the new flag `-fno-load-initial-targets` which doesn't load all `Target`s
immediately but only computes the module graph for all `Target`s.
The user can then decide to load modules from that module graph using
the syntax:

    ghci> :reload <Mod>

This will load everything in the module graph up to `Mod`.

The user can return to the initial state by using the builtin target
`none` to unload all modules.

    ghci> :reload none

Is in principle identical to starting a new session with the
`-fno-load-initial-targets` flag.

The `-fno-load-initial-targets` flag allows for faster startup time of GHCi when a
user has lots of `Target`s.

We additionally extend the `:reload` command to accept multiple
`ModuleName`s. For example:

    ghci> :reload <Mod1> <Mod2>

Loads all modules up to the modules `Mod1` and `Mod2`.

49f44e52

by Teo Camarasu at 2025-06-26T04:19:51-04:00

Expose ghc-internal unit id through the settings file

This in combination with the unit id of the compiler library allows
cabal to know of the two unit ids that should not be reinstalled (in
specific circumstances) as:
- when using plugins, we want to link against exactly the compiler unit
id
- when using TemplateHaskell we want to link against exactly the package
that contains the TemplateHaskell interfaces, which is `ghc-internal`

See: <https://github.com/haskell/cabal/issues/10087>

Resolves #25282

499c4efe

by Bryan Richter at 2025-06-26T04:20:33-04:00

CI: Fix and clean up capture of timings

* Fixes the typo that caused 'cat ci-timings' to report "no such file or
  directory"
* Gave ci_timings.txt a file extension so it may play better with other
  systems
* Fixed the use of time_it so all times are recorded
* Fixed time_it to print name along with timing

86c90c9e

by Bryan Richter at 2025-06-26T04:20:33-04:00

CI: Update collapsible section usage

The syntax apparently changed at some point.

04308ee4
by Bryan Richter at 2025-06-26T04:20:33-04:00
```
CI: Add more collapsible sections
```

43b606bb

by Florian Ragwitz at 2025-06-27T16:31:26-04:00

Tick uses of wildcard/pun field binds as if using the record selector function

Fixes #17834.

See Note [Record-selector ticks] for additional reasoning behind this as well
as an overview of the implementation details and future improvements.

d4952549

by Ben Gamari at 2025-06-27T16:32:08-04:00

testsuite/caller-cc: Make CallerCc[123] less sensitive

These were previously sensitive to irrelevant changes in program
structure. To avoid this we filter out all by lines emitted by the
-fcaller-cc from the profile.

8d33d048

by Berk Özkütük at 2025-07-07T20:42:20-04:00

Consider `PromotedDataCon` in `tyConStupidTheta`

Haddock checks data declarations for the stupid theta so as not to
pretty-print them as empty contexts. Type data declarations end up as
`PromotedDataCon`s by the time Haddock performs this check, causing a
panic. This commit extends `tyConStupidTheta` so that it returns an
empty list for `PromotedDataCon`s. This decision was guided by the fact
that type data declarations never have data type contexts (see (R1) in
Note [Type data declarations]).

Fixes #25739.

a26243fd

by Ryan Hendrickson at 2025-07-07T20:43:07-04:00

haddock: Document instances from other packages

When attaching instances to `Interface`s, it isn't enough just to look
for instances in the list of `Interface`s being processed. We also need
to look in the modules on which they depend, including those outside of
this package.

Fixes #25147.
Fixes #26079.

0fb24420

by Rodrigo Mesquita at 2025-07-07T20:43:49-04:00

hadrian: Fallback logic for internal interpreter

When determining whether to build the internal interpreter, the `make`
build system had a fallback case for platforms not in the list of
explicitly-supported operating systems and architectures.

This fallback says we should try to build the internal interpreter if
building dynamic GHC programs (if the architecture is unknown).

Fixes #24098

fe925bd4
by Ben Gamari at 2025-07-07T20:44:30-04:00
```
users-guide: Reference Wasm FFI section
```
5856284b
by Ben Gamari at 2025-07-07T20:44:30-04:00
```
users-guide: Fix too-short heading warning
```

a48dcdf3