GHC 9.4.1-alpha1 now available

Ben Gamari ben at
Sun May 1 23:17:01 UTC 2022

The GHC developers are happy to announce the availability of the first
alpha release of the GHC 9.4 series. Binary distributions, source
distributions, and documentation are available at

This major release will include:

 - A new profiling mode, `-fprof-late`, which adds automatic cost-center
   annotations to all top-level functions *after* Core optimisation has
   run. This incurs significantly less performance cost while still
   providing informative profiles.

 - A variety of plugin improvements including the introduction of a new
   plugin type, *defaulting plugins*, and the ability for typechecking
   plugins to rewrite type-families.

 - An improved constructed product result analysis, allowing unboxing of
   nested structures, and a new boxity analysis, leading to less reboxing.

 - Introduction of a tag-check elision optimisation, bringing
   significant performance improvements in strict programs.

 - Generalisation of a variety of primitive types to be levity
   polymorphic. Consequently, the `ArrayArray#` type can at long last be
   retired, replaced by standard `Array#`.

 - Introduction of the `\cases` syntax from [GHC proposal 0302]

 - A complete overhaul of GHC's Windows support. This includes a
   migration to a fully Clang-based C toolchain, a deep refactoring of
   the linker, and many fixes in WinIO.

 - Support for multiple home packages, significantly improving support
   in IDEs and other tools for multi-package projects.

 - A refactoring of GHC's error message infrastructure, allowing GHC to
   provide diagnostic information to downstream consumers as structured
   data, greatly easing IDE support.

 - Significant compile-time improvements to runtime and memory consumption.

 - ... and much more

We would like to thank Microsoft Azure, GitHub, IOHK, the Zw3rk
stake pool, Tweag I/O, Serokell, Equinix, SimSpace, 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.

Happy testing,

- Ben

[GHC proposal 0302]: 
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