Techniques for Tracing Constraints

Question

Here\'s the scenario: I\'ve written some code with a type signature and GHC complains could not deduce x ~ y for some x and y. You can usually throw GH

Answer 1

Did you try this in GHC 8.8+?

share :: (Let :<: sup,
          Domain a ~ sup,
          Domain b ~ sup,
          SyntacticN (a -> (a -> b) -> b) fi,
          _) 
      => a -> (a -> b) -> a
share = sugarSym Let

The key is to use type hole among constraints: _ => your difficult type