RepPolyPatBind.hs:18:5: error: [GHC-55287]
    • The pattern binding does not have a fixed runtime representation.
      Its type is:
        p0 :: TYPE c0
      Cannot unify ‘TupleRep [rep, rep]’ with the type variable ‘c0’
      because it is not a concrete ‘RuntimeRep’.
    • In the pattern: (# x, y #)
      In a pattern binding: (# x, y #) = undefined
      In the expression:
        let
          x, y :: a
          (# x, y #) = undefined
        in x
    • Relevant bindings include
        foo :: () -> a (bound at RepPolyPatBind.hs:15:1)

RepPolyPatBind.hs:18:5: error: [GHC-55287]
    • • The binder ‘y’ does not have a fixed runtime representation.
        Its type is:
          a :: TYPE rep
      • The binder ‘x’ does not have a fixed runtime representation.
        Its type is:
          a :: TYPE rep
    • In the expression:
        let
          x, y :: a
          (# x, y #) = undefined
        in x
      In an equation for ‘foo’:
          foo _
            = let
                x, y :: a
                (# x, y #) = undefined
              in x