What is your recent (>= GHC 9.4) experience using Template Haskell?

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While we are piling on Generics, here are my own gripes about it:

  • The naming – M1 S1 U1 K1 etc., despite doing a lot of generics programming over the years I have never gotten a good intuition for which is which.
  • How much overhead is necessitated when/if GHC fails to inline away things going through a generic Rep and how slow all that inliner work is. It would be much much better IMO if the generic representation was a flat SOP representation like in Data.Record.Generic
  • Finally: why aren’t documentation comments in Meta? That’d be such a nice feature for many encoder/decoder libraries. Basically the same gripe applies for TH though.
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