{
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  "path": "/t/type-level-programming-dealing-with-ambiguous-type-error/13828#post_12",
  "publishedAt": "2026-04-14T07:27:15.000Z",
  "site": "https://discourse.haskell.org",
  "textContent": "tomjaguarpaw:\n\n> What _will_ allow you to do that is `forall ->`.\n\nNo, matching on types is not (and should not be) possible even with full dependent types like in Agda. I hope this is not a planned feature.\n\nWhat you can do is create a data type and map that to the type level:\n\n\n    data MyType = TInt | TBool\n\n    typeOfMyType :: MyType -> Type\n    typeOfMyType TInt = Int\n    typeOfMyType TBool = Bool\n\n    negateLike :: forall (t :: MyType) -> typeOfMyType t -> typeOfMyType t\n    negateLike TInt x = -x\n    negateLike TBool x = not x\n",
  "title": "Type level programming: Dealing with ambiguous type error"
}