I'm not sure if this has been pointed out already, but beyond turning a
proper grammar into a stringly-typed one, shoehorning some features of
.cabal files into YAML syntax really appear like a case of the "Genius
Tailor"[1], e.g. consider the `hpack` example

   when:
     - condition: flag(fast)
       then:
         ghc-options: -O2
       else:
         ghc-options: -O0