-
4354218f
by Adam Gundry at 2026-03-19T08:23:57-04:00
ghci: Mention active language edition in startup banner
Per GHC proposal 632, this makes the GHCi startup banner include
the active language edition, plus an indication of whether this
was the default (as opposed to being explicitly selected via an
option such as `-XGHC2024`). For example:
```
$ ghci
GHCi, version 9.14.1: https://www.haskell.org/ghc/ :? for help
Using default language edition: GHC2024
ghci>
```
Fixes #26037.
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04895566
by Sylvain Henry at 2026-03-19T08:24:26-04:00
Check that shift values are valid
In GHC's codebase in non-DEBUG builds we silently substitute shiftL/R
with unsafeShiftL/R for performance reasons. However we were not
checking that the shift value was valid for unsafeShiftL/R, leading to
wrong computations, but only in non-DEBUG builds.
This patch adds the necessary checks and reports an error when a wrong
shift value is passed.
-
2b5a4872
by Sylvain Henry at 2026-03-19T08:24:26-04:00
Implement basic value range analysis (#25718)
Perform basic value range analysis to try to determine at compile time
the result of the application of some comparison primops (ltWord#, etc.).
This subsumes the built-in rewrite rules used previously to check if one
of the comparison argument was a bound (e.g. (x :: Word8) <= 255 is
always True). Our analysis is more powerful and handles type
conversions: e.g. word8ToWord x <= 255 is now detected as always True too.
We also use value range analysis to filter unreachable alternatives in
case-expressions. To support this, we had to allow case-expressions for
primitive types to not have a DEFAULT alternative (as was assumed before
and checked in Core lint).
-
26e6a745
by sheaf at 2026-03-19T08:24:43-04:00
Improve incomplete record selector warnings
This commit stops GHC from emitting spurious incomplete record selector
warnings for bare selectors/projections such as .fld
There are two places we currently emit incomplete record selector
warnings:
1. In the desugarer, when we see a record selector or an occurrence
of 'getField'. Here, we can use pattern matching information to
ensure we don't give false positives.
2. In the typechecker, which might sometimes give false positives but
can emit warnings in cases that the pattern match checker would
otherwise miss.
This is explained in Note [Detecting incomplete record selectors]
in GHC.HsToCore.Pmc.
Now, we obviously don't want to emit the same error twice, and generally
we prefer (1), as those messages contain fewer false positives. So we
suppress (2) when we are sure we are going to emit (1); the logic for
doing so is in GHC.Tc.Instance.Class.warnIncompleteRecSel,
and works by looking at the CtOrigin.
Now, the issue was that this logic handled explicit record selectors as
well as overloaded record field selectors such as "x.r" (which turns
into a simple GetFieldOrigin CtOrigin), but it didn't properly handle
record projectors like ".fld" or ".fld1.fld2" (which result in other
CtOrigins such as 'RecordFieldProjectionOrigin').
To solve this problem, we re-use the 'isHasFieldOrigin' introduced in
fbdc623a (slightly adjusted).
On the way, we also had to update the desugarer with special handling
for the 'ExpandedThingTc' case in 'ds_app', to make sure that
'ds_app_var' sees all the type arguments to 'getField' in order for it
to indeed emit warnings like in (1).
Fixes #26686
-
6ead1bbf
by Cheng Shao at 2026-03-19T08:24:45-04:00
rts: opportunistically grow the MutableByteArray# in-place in resizeMutableByteArray#
Following !15234, this patch improves `resizeMutableByteArray#` memory
efficiency by growing the `MutableByteArray#` in-place if possible,
addressing an old todo comment here. Also adds a new test case
`resizeMutableByteArrayInPlace` that stresses this behavior.
-
4b1ff14e
by Zubin Duggal at 2026-03-19T08:24:46-04:00
compiler/ffi: Collapse void pointer chains in capi wrappers
New gcc/clang treat -Wincompatible-pointer-types as an error by
default. Since C only allows implicit conversion from void*, not void**,
capi wrappers for functions taking e.g. abstract** would fail to compile
when the Haskell type Ptr (Ptr Abstract) was naively translated to void**.
Collapse nested void pointers to a single void* when the pointee type
has no known C representation.
Fixes #26852
-
c0b5e874
by Teo Camarasu at 2026-03-19T08:24:47-04:00
ghc-internal: Float Generics to near top of module graph
We remove GHC.Internal.Generics from the critical path of the
`ghc-internal` module graph. GHC.Internal.Generics used to be in the
middle of the module graph, but now it is nearer the top (built later).
This change thins out the module graph and allows us to get rid of the
ByteOrder hs-boot file.
We implement this by moving Generics instances from the module where the
datatype is defined to the GHC.Internal.Generics module. This trades off
increasing the compiled size of GHC.Internal.Generics with reducing the
dependency footprint of datatype modules.
Not all instances are moved to GHC.Internal.Generics. For instance,
`GHC.Internal.Control.Monad.Fix` keeps its instance as it is one of the
very last modules compiled in `ghc-internal` and so inverting the
relationship here would risk adding GHC.Internal.Generics back onto the
critical path.
We also don't change modules that are re-exported from the `template-haskell` or `ghc-heap`.
This is done to make it easy to eventually move `Generics` to `base`
once something like #26657 is implemented.
Resolves #26930
Metric Decrease:
T21839c
-
511afa7e
by Luite Stegeman at 2026-03-19T08:25:01-04:00
Move some functions related to pointer tagging to a separate module
-
316ec094
by Luite Stegeman at 2026-03-19T08:25:01-04:00
Branchless unpacking for enumeration types
Change unpacking for enumeration types to go to Word8#/Word16#/Word#
directly instead of going through an intermediate unboxed sum. This
allows us to do a branchless conversion using DataToTag and TagToEnum.
Fixes #26970
-
14aad09b
by Luite Stegeman at 2026-03-19T08:25:06-04:00
bytecode: Carefully SLIDE off the end of a stack chunk
The SLIDE bytecode instruction was not checking for stack chunk
boundaries and could corrupt the stack underflow frame, leading
to crashes.
We add a check to use safe writes if we cross the chunk boundary
and also handle stack underflow if Sp is advanced past the underflow
frame.
fix #27001
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e1e03d27
by Cheng Shao at 2026-03-19T08:25:07-04:00
ghci: serialize BCOByteArray buffer directly when possible
This patch changes the `Binary` instances of `BCOByteArray` to
directly serialize the underlying buffer when possible, while also
taking into account the issue of host-dependent `Word` width. See
added comments and amended `Note [BCOByteArray serialization]` for
detailed explanation. Closes #27020.
-
eaa9beaa
by Matthew Pickering at 2026-03-19T08:25:15-04:00
Use OsPath rather than FilePath in Downsweep cache
This gets us one step closure to uniformly using `OsPath` in the
compiler.
-
93de2b51
by Cheng Shao at 2026-03-19T08:25:17-04:00
hadrian: fix ghc-in-ghci flavour stage0 shared libraries
This patch fixes missing stage0 shared libraries in hadrian
ghc-in-ghci flavour, which was accidentally dropped in
669d09f950a6e88b903d9fd8a7571531774d4d5d and resulted in a regression
in HLS support on linux/macos. Fixes #27057.
-
fea35103
by Cheng Shao at 2026-03-19T08:25:17-04:00
ghc-internal: fix unused imports again
Fixes #27059.
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54456a53
by Sylvain Henry at 2026-03-19T08:25:23-04:00
JS: install rts/Types.h header file (#27033)
It was an omission, making HsFFI.h not usable with GHC using the JS
backend.
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b9918009
by Cheng Shao at 2026-03-19T08:25:25-04:00
hadrian: don't compile RTS with -Winline
This patch removes `-Winline` from cflags when compiling the RTS,
given that:
1. It generates a huge pile of spam and hurts developer experience
2. Whether inlining happens is highly dependent on toolchains,
flavours, etc, and it's not really an issue to fix if inlining
doesn't happen; it's a hint to the C compiler anyway.
Fixes #27060.
-
f55d53f3
by Cheng Shao at 2026-03-19T08:25:25-04:00
hadrian: compile libffi-clib with -Wno-deprecated-declarations
This patch adds `-Wno-deprecated-declarations` to cflags of
`libffi-clib`, given that it produces noise at compile-time that
aren't really our issue to fix anyway, it's from vendored libffi
source code.