Error found:
in module Main
at tests/purs/failing/3531-6.purs:21:7 - 21:27 (line 21, column 7 - line 21, column 27)

  No type class instance was found for
             
    Main.C a4
           b5
             
  The following instances partially overlap the above constraint, which means the rest of their instance chains will not be considered:

    instance in module Main with type forall a. C String (Array a) (line 9, column 1 - line 10, column 15)
    instance in module Main with type C Int Int (line 14, column 1 - line 15, column 15)


while applying a function c
  of type C @t0 @t1 t2 t3 => Proxy @t0 t2 -> Proxy @t1 t3 -> Boolean
  to argument Proxy
while inferring the type of c Proxy
in value declaration fn

where a4 is a rigid type variable
        bound at (line 0, column 0 - line 0, column 0)
      b5 is a rigid type variable
        bound at (line 0, column 0 - line 0, column 0)
      t0 is an unknown type
      t1 is an unknown type
      t2 is an unknown type
      t3 is an unknown type

See https://github.com/purescript/documentation/blob/master/errors/NoInstanceFound.md for more information,
or to contribute content related to this error.