Error found:
in module UnknownSuperclassTypeVar
at tests/purs/failing/Superclasses3.purs:8:12 - 8:13 (line 8, column 12 - line 8, column 13)

  Type variable b is undefined.

while inferring the kind of b
while checking that type b
  has kind t0
while inferring the kind of Foo$Dict b
while inferring the kind of Record () -> Foo$Dict b
while inferring the kind of ( "Foo0" :: Record () -> Foo$Dict b
                            )                                  
while inferring the kind of { "Foo0" :: Record () -> Foo$Dict b
                            }                                  
in type constructor Bar$Dict

where t0 is an unknown type

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