GHC 9.14.1-alpha1 is now available

bgamari - 2025-08-19

The GHC developers are very pleased to announce the availability of the first alpha prerelease of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at downloads.haskell.org.

GHC 9.14 will bring a number of new features and improvements, including:

  • Significant improvements in specialisation:

    • The SPECIALISE pragma now allows use of type application syntax

    • The SPECIALISE pragma can be used to specialise for expression arguments as well as type arguments.

    • Specialisation is now considerably more reliable in the presence of newtypes

    • the specialiser is now able to produce specialisations with polymorphic typeclass constraints, considerably broadening its scope.

  • Significant improvements in the GHCi debugger

  • Record fields can be defined to be non-linear when LinearTypes is enabled.

  • RequiredTypeArgments can now be used in more contexts

  • SSE/AVX support in the x86 native code generator backend

  • A major update of the Windows toolchain

  • … and many more

A full accounting of changes can be found in the release notes. Given the many specialisation improvements and their potential for regression, we would very much appreciate testing and performance characterisation on downstream workloads.

Due to unexpected complications, this initial prerelease comes a bit later than expected. Consequently, we expect to have three condensed alphas prior to the release candidate, in contrast to the scheduled three. We expect the next alpha will come the seek of 9 Sept. 2025, while the third will come 23 Sept. 2025, with the release candidate coming 7 Oct. 2025.

We would like to thank the Zw3rk stake pool, Well-Typed, Mercury, Channable, Tweag I/O, Serokell, SimSpace, the Haskell Foundation, and other anonymous contributors whose on-going financial and in-kind support has facilitated GHC maintenance and release management over the years. Finally, this release would not have been possible without the hundreds of open-source contributors whose work comprise this release.

As always, do give this release a try and open a ticket if you see anything amiss.