-
1b4a622f
by sheaf at 2026-09-17T02:39:13-04:00
Improvements to type/data family handling
This commit makes several improvements to the treatment of type and data
families in GHC:
- We consistently use "type family" instead of "type synonym family"
to avoid a confusion with type synonyms. For example:
- OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon
- ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon
- Various functions that were specific to data families have been
renamed to make this clear. For example:
- tyConFamInst_maybe ==> tyConDataFamInst_maybe
- isFamInstTyCon ==> isDataFamInstTyCon
- 'FamTyConFlav' has been refactored so that all closed type families
share a single 'ClosedTypeFamilyTyCon' constructor.
The corresponding 'IfaceFamTyConFlav' type was updated similarly.
This is then used to tidy up the implementation of
GHC.Core.FamInstEnv.reduceTyFamApp_maybe.
-
c5aa9098
by sheaf at 2026-09-17T02:39:13-04:00
Small refactor of lookupFamInstEnv
This commit reworks the code for looking up family instances in
GHC.Core.FamInstEnv, reducing duplication a little bit.
No change in behaviour.
-
a3ad4588
by sheaf at 2026-09-17T02:39:14-04:00
Use a type family for boxing unboxed types
This commit overhauls the way in which unboxed types are boxed, as per
the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box.
The main change is to allow boxing to be parametrised by representation,
e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box'
using a closed type family:
newtype Box (a :: TYPE r) = Box (BoxTF r)
type BoxTF :: RuntimeRep -> Type
type family BoxTF r where
BoxTF IntRep = BoxInt
BoxTF Int8Rep = BoxInt8
BoxTF WordRep = BoxWord
BoxTF LiftedRep = Any @Type
BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2)
...
BoxTF (SumRep rs) = BoxSum rs
This new design solves the following problems:
- It allows boxing a type whose 'RuntimeRep' has not yet been
determined (e.g. because we only learn the 'RuntimeRep' after
constraint solving). That is, 'Box @r a' is a perfectly valid type
even if 'r' is an unfilled metavariable. This is a requirement
to fix #25065 (in which we need to box a type whose 'RuntimeRep'
is only filled in during constraint solving).
- It handles boxing of unboxed tuples and unboxed sums, via recursive
boxing. See Note [Boxing TupleRep and SumRep] in
GHC.Builtin.WiredIn.Types.Box.
'Box', 'BoxTF' and all of the boxing data constructors are defined in
a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains
nothing but wired-in declarations, and GHC never loads its interface on
account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule);
see Note [Loading instances for wired-in things] in GHC.Iface.Load.
The individual boxing data constructors are deliberately left as an
internal implementation detail, and not exported. The intended API is
via the two new magic 'Id's:
box :: forall {r} (a :: TYPE r). a -> Box a
unbox :: forall {r} (a :: TYPE r). Box a -> a
exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing
data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer
exported from base (CLC proposal #421).
We use this new design to consistently desugar:
- parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt})
- then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt})
- recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo)
- arrows (GHC.HsToCore.Arrows)
by consistently using 'box'/'unbox' to deal with unboxed types being put
into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}'
to create fresh /representation-polymorphic/ type variables for the
binders that we are going to put into a big tuple (previously, GHC only
allowed lifted types in that position).
These desugaring of box and unbox is explained in
Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking,
the desugaring looks like:
box @r @ty e ==> K e
unbox @r @ty e ==> case e of K x -> x
where 'K' is the boxing data constructor at RuntimeRep 'r'. It's
slightly more complicated than that in practice: we first need to
insert a cast (see Note [The canonical type of a RuntimeRep]) using the
new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need
recursive logic explained in Note [box/unbox for unboxed tuples and sums],
including a specific 'BoxSum' datatypes for unboxed sum (which also
needed a wired-in type-level list indexing type family (!!)).
The desugaring happens in two ways:
- Occurrences of 'box'/'unbox' emitted by the typechecker are
eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr.
- Other code that needs to box/unbox emits the appropriate code inline.
This includes the big tuple machinery of GHC.Core.Make used by the
desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as
the float-out pass (GHC.Core.Opt.SetLevels).
Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring.
On the way, we overhaul the litany of big tuple functions by introducing
data BigTupleLayout = BoxedElements | BareElements
to distinguish the two kinds of "big tuples" that GHC routinely deals
with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'.
All of this code is moved to the new module GHC.Core.Make.BigTuple.
Fixes #20864 #22336 #22473 #25065 #27331
-------------------------
Metric Decrease:
T9872a
-------------------------
-
4cf7628a
by Evgeny Malyshev at 2026-09-17T02:39:56-04:00
Fix the CompactionFailed documentation link to compact
The old Haddock reference links into base instead of ghc-compact.
Use an explicit URL because ghc-compact depends on base, not vice versa.
Fixes #27558
Assisted-By: OpenAI Codex
-
098bba70
by Facundo Domínguez at 2026-09-17T14:57:41-04:00
Remove the call to hoistFlag from processCmdLineP
This call was undesirable because it was causing a reconstruction
of the list of flag processors.
Even relying on list fusion would not be sufficient because we want
to replace the list with a data structure with faster lookups to
address #25763.
The removal is done in two moves:
* We move CmdLineP to CmdLine.hs
* Then we move the effect of hoisting to processArgs via a new function
hoistEwM
-
e01799c7
by Facundo Domínguez at 2026-09-17T14:57:42-04:00
Do not create duplicate flag processors for the -W flag
This makes simpler implementing the command line parser with a trie map
holding flag processors. If we were to allow duplicate flag processors
for any flag, the trie map would need to be a multimap.
-
3875b257
by Facundo Domínguez at 2026-09-17T14:57:42-04:00
Replace the list of flag processors with a trie map in `processArgs`
Previously `GHC.Driver.CmdLine.findArg` was called for each
command-line argument, doing a linear search on the list of flag
processors each time. This was somewhat costly as the list of flag
processor has near 2000 elements.
A lookup with a trie map is faster in general, but the speed up is
only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient
times, so the amount of lookups piles up. This could happen in large
projects with many units each having many dependencies. If only a
module needs to be recompiled, the user still needs to wait for all of
the flag parsing to complete.
The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a
10x speed up when using the trie.
The trie map is implemented in `GHC.Data.StringTrie`.
The design is explained in Note [Processing command line argument fast]
in GHC.Driver.Session.
The commit also:
* adds two property-based tests for trie map operations,
* adds a benchmark of the command line parser, and
* renames the predicate `arg_ok` to `valid_flag_suffix` to decide what
flag processor should be used when there are multiple matching
prefixes on a flag.
Fixes #25763.
-
5236634a
by Andreas Klebinger at 2026-09-17T14:58:24-04:00
Compile Word64{Map,Set} with -O2 always.
This is the hottest code and even if we build GHC with -O0 otherwise -O2
pays off for these modules.
Fixes #27814.
-
545fd4fb
by ARATA Mizuki at 2026-09-22T15:03:24-04:00
Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types
bitReverse{16,32}# and byteSwap{16,32}# have the type
Word# -> Word#, but their C correspondents took and
returned StgWord{16,32}.
The mismatch on bitReverse16# led to the problem reported
in #27299. Although no similar issue is reported for
bitReverse32# and byteSwap{16,32}#, it seemed wise to
change them proactively.
This commit fixes the mismatch by changing the C type.
Fixes #27299
-
bf17f289
by fendor at 2026-09-22T15:04:05-04:00
Don't lose instances from shadowed imported modules with the same name
When we look for instances below the current module, we need to check
the unit id as well when we check for whether the module is the current
module, otherwise we ignore modules we import that have the same name as
the import module.
Adds regression test.
-
53eead15
by Wolfgang Jeltsch at 2026-09-24T20:12:03-04:00
Correct the documentation of `explicitUnits`
Resolves #27787.
-
35bf6f4b
by Simon Jakobi at 2026-09-24T20:12:49-04:00
Remove stale specHeader bullet from Note [Don't make fillers for constraint types]
The Note said that Specialise.specHeader also calls mkAbsentFiller.
abfc224a27c removed that call: the specialiser no longer drops dead
arguments at all, see Note [Do not drop dead args from specialisations]
in GHC.Core.Opt.Specialise.
Assisted-by: Claude Fable 5.1
-
1abef1ef
by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00
Improve the `mhu-closure` makefile
-
a79a68ea
by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00
Make `ghci-multi` hide all unneeded packages
-
d6e72450
by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00
Improve the definition of the home unit closure property
-
c9a2766d
by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00
Re-implement the home unit closure check
Compared to the previous implementation, the new one has the following
advantages:
* It is correct.
- It distinguishes between units that have the same unit ID but
different ABI hashes.
- When `-hide-all-packages` is not used, it considers as home unit
dependencies also units that are made implicitly available
because they are in the package database.
* It seems to be faster in usual settings.
- In particular, it does not have a preparation phase in which it
merges the dependency information from all home units, so that
its running time does not grow linearly with the size of the
package database in normal Cabal scenarios.
* It is (hopefully) clearer.
* It is better documented.
-
fa96acf8
by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00
Remove erroneous GHC flag in `hadrian-multi`
The flag was `-Werror=-Wno-error=incomplete-record-selectors`. Its
purpose was to permit incomplete record selectors, but because of the
illegal combination of `-Werror=` and `-Wno-error` it was ignored,
without any negative consequences.
-
9f48a5b9
by Alan Zimmerman at 2026-09-25T17:02:50-04:00
EPA: Add specific layout field to AnnList
Up to now AnnList has effectively served to represent lists of things
having layout, regardless of whether they do or not.
In Haskell, layout is optional in many places, as there is also an
alternative syntax using braces and semi-colons, which is free-form.
This commit introduces AnnListLayout, a data structure capturing this
distinction.
It is deliberately set up similarly to EpLayout, so that these two can
be merged in time.
The transition is done mechanically, where AnnListBraces is not used
yet, the original Nothing case maps to AnnListNoLayout, and the Just
case to AnnListLayout.
Later commits will fine tune these against the actual parser layout.
-
234bab08
by Vladislav Zavialov at 2026-09-29T17:22:54-04:00
Add regression test for #7803
Commit 2effe18ab5, first shipped with GHC 8.2.1, fixed #7803 "Superclass
methods are left unspecialized".
This change turns the example from the ticket description into a regression
test, checking that foo1 is fully specialised at Double, with no calls to the
overloaded exp5Tail.
Closes #7803
Assisted-by: Claude Opus 5
-
c406135c
by Andreas Klebinger at 2026-10-01T06:57:28-04:00
RTS: Update flag parsing/handling:
Using 0 as argument to any of these flags now resets the flags setting to default:
- ``-n0`` disables nursery chunking.
- ``-K0`` (or a bare ``-K``) removes the stack size limit.
- ``-M0`` removes the heap size limit.
- ``-H0`` resets the suggested heap size, including the nursery scaling set by ``-H``.
- ``-AL0`` makes the large object allocation limit follow ``-A`` again.
GC Generations are now limited to 64.
-n larger than -A now emits a warning and disables chunking.
Fixes #27830 #27829
-
984ee82b
by Andreas Klebinger at 2026-10-01T06:58:10-04:00
Fix MultiLayerModules timeout multiplier.
We accidentally used the compile multiplier for ghci commands which
use the run timeout setting to set the timeout.
Fixes #26263 and #27796.
-
50a9cf26
by Andreas Klebinger at 2026-10-01T06:58:10-04:00
testsuite: Include runtime in JUnit report.
-
e358619f
by Alan Zimmerman at 2026-10-01T06:59:01-04:00
EPA: Use EpaLocation in EpVirtualBraces
Haddock processing uses EpLayout.EpVirtualBraces to record the current
layout column, for allocating haddock comments correctly.
For exact printing, we need the line as well as the col, so we know
how many lines to skip when the indented code block starts.
This commit updates EpLayout.EpVirtualBraces so that it carries an
EpaLocation instead of just the Int column, to allow it to be used for
both purposes.
It is a simple mechanical change, with no other impact, but it allows
us to use EpLayout instead of AnnListLayout in AnnList, in the next
commit in this series.
-
1d2a26ee
by Andrew Lelechenko at 2026-10-01T20:22:04-04:00
Remove bitSize from MINIMAL pragma of class Bits
Cf. https://github.com/haskell/core-libraries-committee/issues/441
The function is deprecated for 12 years and has a default implementation,
yet it was never removed from the MINIMAL pragma, putting library authors
in a very awkward position. Let's finally remove bitSize from MINIMAL.
-
3cc21e4c
by Hannes Siebenhandl at 2026-10-01T20:22:59-04:00
Add regression test for #27641
-
c35096f5
by Hannes Siebenhandl at 2026-10-01T20:23:00-04:00
Don't `:add` modules the loader will reject
Only home modules can be actually added to the loader context, thus we
only accept the module if it belongs to a home unit.
-
a563cb27
by Simon Jakobi at 2026-10-02T17:37:36-04:00
ci: accept modified changelog.d entries in lint-changelog
The changelog guide says to extend an existing entry rather than add a
new one when the feature is already documented. lint_changelog only
counted added files, so such MRs failed before the validator ran.
Fixes #27779.
Assisted-by: Claude Fable 5.1
-
03082cd4
by Simon Jakobi at 2026-10-02T17:38:17-04:00
changelog.d: Fix warning flag name in the semaphore-v2 entry
The entry refers to -Wsemaphore-version-mismatch, which does not exist.
The warning GHC emits when it cannot use a -jsem semaphore, including
on a protocol version mismatch, is -Wsemaphore-open-failure.
Context: !15729, #25087
Assisted-by: Claude Fable 5.1
-
a93705ee
by Simon Jakobi at 2026-10-02T17:38:17-04:00
changelog.d: Fix the CLC proposal link in the T27455 entry
The entry used the Sphinx :ref: role with a URL as its target. :ref:
resolves only internal labels, so the generated release notes would
show the proposal name without a link. Use the plain hyperlink form
like the other entries.
Context: !16274, #27455
Assisted-by: Claude Fable 5.1
-
54381079
by Hannes Siebenhandl at 2026-10-02T17:39:01-04:00
Extend the `TrustOverlay` for wired-in units
The TrustOverlay only contained the `UnitId` of all on-disk units.
However, wired-in units are referred to by their wired-in unit id, which
is not the same as the on-disk unit id.
Thus, trust checks for wired-in units failed because the lookup was
using the wired-in unit, which wasn't present in the `TrustOverlay`.
We fix #27834, by copying the trust info for wired-in unit ids.
-
f8cfb1a5
by Hécate Kleidukos at 2026-10-04T19:36:39+02:00
[CLC 341] Strict variants of mutable types
This commit is the implementation of CLC Proposal 341
https://github.com/haskell/core-libraries-committee/issues/341
-
575c4bc6
by Rodrigo Mesquita at 2026-10-05T12:32:02-04:00
ttg: HsModuleName in the AST, ModuleName in GHC
This commit makes the AST fully independent from GHC by parsing a
"module name" as an `HsModuleName (= HText)` rather than constructing an
`ModuleName (= FastString)` straight away.
In the GHC side, everything remains as a `ModuleName`. We turn AST
`HsModuleName`s into fast strings with the cheap `mkFastStringShortText`
when we process the AST for manipulation within the compiler.
There are no performance regressions introduced by this approach.
This is the final piece of #21592
Alternative plans were discussed in
gitlab.haskell.org/ghc/ghc/-/merge_requests/16546#note_694647,
but the Simon suggested one won in simplicity and performance when
compared against my attempt at implementing my original plan of having
a family `ModuleNameP`.
-
b3b89d32
by mangoiv at 2026-10-05T22:03:32-04:00
hadrian: Persist the used flavour name in the build root (#20650)
This executes the idea proposed in #20650, teaching Hadrian to persist
the flavour used to build a build root. This both makes use of multiple
build roots more ergonomic (as the user no longer needs to repeat
themselves) and avoids a tiresome foot-gun (forgetting to specify a
flavour, often wholly invalidating a build root).
Closes #20650.
Co-authored-by: Sylvain Henry <sylvain@haskus.fr>
-
f977837b
by mangoiv at 2026-10-05T22:04:21-04:00
configure: fix sed script and subst tooldir script
Fixes #27672
Adds sanity checking for SUBST_TOOLDIR
Metric Decrease:
LinkableUsage01
MultiLayerModulesTH_OneShot
T10547
T12234
T12425
T13035
T13820
T18140
T18730
T18923
T9198
TcPlugin_RewritePerf
mhu-perf
-
f1cb08be
by Hannes Siebenhandl at 2026-10-05T22:05:03-04:00
Prepend in-memory unit database for backpack
The packageDbFlags are stored in reverse order. Thus, prepending will
ensure that the in-memory unit database is the last item on the unit
database stack.
Further, the in-memory unit database needs to be able to shadow units
from earlier unit databases in the unit database stack.
Moreover, a `-clear-package-db` would remove the in-memory database if
it weren't the last item on the stack.
Closes #27835
-
8d49ed42
by Kazu Yamamoto at 2026-10-06T19:37:25-04:00
Do not leave standard file descriptors free at startup (#24450)
A process may be started with stdout closed -- `prog >&-` from a shell does
exactly that. Nothing then reserves descriptor 1, and open(), pipe() and
socket() hand out the lowest free descriptor, so the next descriptor the
runtime creates for itself takes it: the ticker's pipe, or a capability's IO
manager control pipe.
'GHC.Internal.IO.StdHandles.stdout' is a CAF, built the first time the program
writes to stdout, which is long after that has happened. It builds a 'Handle'
over descriptor 1, which now belongs to the runtime, and nothing reports an
error because the descriptor is perfectly good. The program then writes its
output into the runtime's own plumbing.
What that looks like from the outside is a hang. The descriptor the Handle has
taken over is the read end of a pipe, so poll() for POLLOUT on it never says
yes and epoll_ctl() accepts a registration for it; the thread waiting to write
blocks for ever. Closing the Handle at exit closes the runtime's descriptor,
which is worse: the ticker then fails on every tick.
'hs_init_ghc' now opens /dev/null onto whichever of descriptors 0, 1 and 2 are
closed, before the runtime creates any descriptor of its own. Each is opened
for the access that descriptor would normally have, read-only for 0 and
write-only for 1 and 2, so that writing to 'stdin' or reading from 'stdout'
still fails rather than quietly succeeding against /dev/null. See
Note [Standard file descriptors must be open].
Moving only the descriptors the runtime opens would not do: the first file the
program itself opened would land on the free number instead. The fix has to
leave no free number. A program run this way therefore finds stdout connected
to /dev/null rather than failing with EBADF on the first write, which is what
such a program would get from most other language runtimes.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
-
65bcf9e9
by Simon Jakobi at 2026-10-06T19:38:09-04:00
changelog: Repair the sentence describing #27477
The description read "programs using could crash", the object of
"using" having been lost. The synopsis already says which programs are
affected, so drop the dangling word.
Assisted-by: Claude Fable 5.1
-
15ece296
by mangoiv at 2026-10-08T15:14:56-04:00
ci: move hadrian/ghci into the lint category so it can be picked up by more runners
Fixes #27817
-
c0823135
by mangoiv at 2026-10-08T15:14:56-04:00
ci: make lint-adjacent jobs into platform independent
- move lint jobs into lint-anyarch tag
- unify lint jobs under the same platform independent container
-
f76464cf
by Zubin Duggal at 2026-10-08T15:15:39-04:00
DmdAnal: Make AbsDmd neutral in maxDmd
fixes #27845
-
0846506b
by Simon Peyton Jones at 2026-10-09T10:48:20+01:00
Redesign the noinline magic
Main idea:
* When simplifying `noinline (f e1 e2)`, switch off inlining when simplifying `f`
* Mechanism: see `simplOutId`, the `noinlineIdKey` case
* If we see `noinline (f e1) e2`, the simplifier moves the `e2` inside; see the `splitContArgs` call.
This is important so you can write `noinliine f e1 e2` and have it mean the same as `noinline (f e1 e2)`.
* Now `f` sees all its arguments, henc:
* Fixes #27724
* Fixes #23911
* Also fixes #27803 where we were not respecting `noinline` if the RHS
was trivial
See Note [noinlineId magic] for lots of specifics. It's surprisingly tricky!
For some reason a couple of perf tests allocate 1.2% less at compile time,n
namely T29872 and T8095. Geom mean decease of 0.1%
Metric Decrease:
T9872d