Error found:
in module Main
at tests/purs/failing/3531.purs:16:7 - 16:27 (line 16, column 7 - line 16, column 27)

  No type class instance was found for
             
    Main.C a2
             
  The following instance partially overlaps the above constraint, which means the rest of its instance chain will not be considered:

    Main.c1


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

where a2 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

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