Add ghc-9.14 language extensions

[philderbeast]

Fixes #11635. I made similar changes to #10339. The test is the updated md5 check.

Important

Will this need a backport?

---

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
  • Is the change significant? If so, remember to add significance: significant in the changelog file.
• The documentation has been updated, if necessary.
• Manual QA notes have been included.
• Tests have been added. (Ask for help if you don’t know how to write them! Ask for an exemption if tests are too complex for too little coverage!)

[geekosaur]

I'm inclined to say yes, since it's arguably a bug fix for the cabal version intended to support 9.14.

Also, this is a step in the release documentation. What went wrong, fellow cabalers?

[Bodigrim]

As a side note, are these tests useful for anything? I only see them being a constant nuisance, which people automatically rebase to reflect changes to GenericPackageDescription.

[philderbeast]

These tests were added in #6255.

The commit, ae33fcf, has this message:

It defines Structured type class, which we use to prepend a hash to cached Binary blobs. Thus we can catch early, if format is changed, avoiding corrupt cache making cabal behave weirdly.

Plenty types got Typeable instances, as it's a superclass of Structured

This commit also introduces new compat modules:

• Distribution.Compat.Typeable with typeRep
• Distribution.Client.Compat.Orphans, to collect at least some orphans into central place.

[Bodigrim]

Will this need a backport?

Absolutely.