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The original was posted on /r/programminglanguages by /u/MysteriousGenius on 2024-11-11 16:49:42+00:00.

Many FP languages like Haskell or Scala have added GADTs much later in their lifetime, sometimes as an afterthough. Some language authors (Phil Freeman from PureScript) resisted adding them at all saying they’d complicate the language (or the compiler, sorry can’t find the quote).

At the same time, to me GADTs on one hand feel like just a natural thing, I would have thought all sum types work that way until I found out it’s a special form. On the other hand… I never needed them in practice.

What are your thoughts? Would it be beneficial if GADT was the only way to define ADT?