graphql-ruby allows scalar types in the Union

[ojab]

Describe the bug

I found kinda related issue #3092 and it was proposed to use wrapper types, but

module Types
  class XxUnionType < GraphQL::Schema::Union
    possible_types GraphQL::Types::Float, GraphQL::Types::String
  end
end

works and generates

union XxUnion = Float | String

It probably shouldn't, because scalar types are not allowed in the unions by the spec (graphql/graphql-spec#215)

Versions

graphql version: 2.0.15

[rmosolgo]

Oops! Agreed this should not be possible.