<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hello ghc-devs,<div class=""><br class=""></div><div class="">This February I did some changes to the parser that require higher rank types support in ‘happy’. Unfortunately, as I discovered, happy’s --coerce option is severely broken in the presence of higher rank types, so I had to disable it. My benchmarks have shown a 10% slowdown from disabling --coerce (<a href="https://gist.github.com/int-index/38af0c5dd801088dc1de59eca4e55df4" class="">https://gist.github.com/int-index/38af0c5dd801088dc1de59eca4e55df4</a>).</div><div class=""><br class=""></div><div class="">Alongside my changes I submitted a pull request to happy which fixes the issue (<a href="https://github.com/simonmar/happy/pull/134" class="">https://github.com/simonmar/happy/pull/134</a>), in the hope that it would get merged, released, and I could re-enable --coerce in GHC ‘happy' configuration.</div><div class=""><br class=""></div><div class="">Unfortunately, my patch has been ignored to this day (for 3 months now), and the performance regression reached 8.8-alpha. We need to act swiftly if we want to avoid a performance regression in the actual release. Here’s what needs to be done:</div><div class=""><br class=""></div><div class="">1. Merge <a href="https://github.com/simonmar/happy/pull/134" class="">https://github.com/simonmar/happy/pull/134</a></div><div class="">2. Release a new ‘happy’</div><div class="">3. (Optional) Specify in GHC’s build system that it builds only with the latest 'happy' release</div><div class="">4. Restore the --coerce option in GHC’s build system ‘happy’ configuration</div><div class="">5. Backport it to the ghc-8.8 branch</div><div class=""><br class=""></div><div class="">I have no access to do 1 & 2, I believe Simon Marlow does. I’d appreciate if someone took care of 3, currently the build system does not install ‘happy’ and assumes a system-wide installation without checking its version. This means that users of all but the newly released version will encounter obscure error messages. We need a version check. Then I will do 4, as planned, and create a merge request for 5.</div><div class=""><br class=""></div><div class="">All the best,</div><div class="">- Vladislav</div></body></html>