Does not build with GHC 9.2 or 9.4

[andreasabel]

GHC 9.2 saw a refactoring of GHC's syntax trees (XRec, GenLocated), so Tags.hs needs to be updated.

Needed if we want to stay on stackage nightly:

• Initial GHC 9.2 bounds commercialhaskell/stackage#6318

[andreasabel]

@asr @nad Do we want to maintain hs-tags? Every GHC release will require us to adapt it to the latest GHC API. There are approximate solutions like hasktags that are less maintenance intensive.

[nad]

Perhaps there is some tool that provides something that is better (like Agda's jump-to-definition feature).

[andreasabel]

Needed if we want to stay on stackage nightly

We dropped out of stackage nightly after 2022-03-17 and are in LTS 19.29 frozen to version 0.1.5.3.

An alternative is https://github.com/arybczak/ghc-tags (currently not in stackage). It aims to the same thing as hs-tags (parse tags via the GHC API), but does not take its configuration from a cabal file:

• Option --cabal to read configuration from a .cabal file? arybczak/ghc-tags#7

Maybe we could use the ghc-tags-core library for the heavy lifting and just keep our front-end:

• https://hackage.haskell.org/package/ghc-tags-core
• https://github.com/coot/ghc-tags-plugin/tree/master/ghc-tags-core

It is licensed under MPL2.0 (Mozilla Public License 2.0) and looks well-maintained (supports GHC 9.4).

[nad]

$ cabal install ghc-tags-core
Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[…]

[andreasabel]

ghc-tags-core builds with 9.2 but currently not 9.4, waiting for a dependency:

trying: filepath-bytestring-1.4.2.1.11 (dependency of ghc-tags-core)

Unfortunately, this dependency does not have a public bug tracker, it's home seems to be a private wiki: https://joeyh.name/code/haskell-filepath-bytestring/

P.S.: Seems I was in this place already one and a half years ago:

• Does not build with GHC 9.0.1 coot/ghc-tags-plugin#50 (comment)

[andreasabel]

Testing that cabal install ghc-tags-core --allow-newer='filepath-bytestring:base' works, I revised the upper bound on base for filepath-bytestring on hackage. So after cabal update, it should build for you, @nad.

[nad]

The Hackage page for filepath-bytestring states that this package is deprecated. This, along with the fact that ghc-tags-core did not build under GHC 9.4.2, suggests to me that ghc-tags-core is not maintained very actively.

[andreasabel]

suggests to me that ghc-tags-core is not maintained very actively.

I'd guess that @coot might have a different opinion on this.

[coot]

It is actively maintained, I haven't yet removed filepath-bytestring mostly because I wanted to try out the next version of filepath (which actually is published now, so thanks for the reminder :)).

Ref coot/ghc-tags-plugin#66.

[coot]

There's a PR which introduces it to arybczak/ghc-tags#8.

[nad]

It is actively maintained

That's good to know. Thanks!

[coot]

A newer version of filepath-bytestring was published, which compiles with ghc-9.4.