fails:Method#arity for a Method generated by respond_to_missing? returns -1
fails:"Method#arity returns negative values for method definition \n    def m(a: 1) end\n    def n(a: 1, b: 2) end"
fails:"Method#arity returns negative values for method definition \n    def m(a=1, b: 2) end\n    def n(*a, b: 1) end\n    def o(a=1, b: 2) end\n    def p(a=1, *b, c: 2, &l) end"
fails:"Method#arity returns negative values for method definition \n    def m(**k, &l) end\n    def n(*a, **k) end\n    def o(a: 1, b: 2, **k) end"
