VariableForce exception thrown (Partial interaction with SaveBang)

[jfelchner]

Running rubocop on my codebase throws an error in the VariableForce cop.

An error occurred while VariableForce cop was inspecting /path/to/my/file.rb.
undefined method `method?' for "s(:pair,\n  s(:sym, :json),\n  s(:lvar, :foo))":RuboCop::AST::PairNode
Did you mean?  method
               methods

Steps to Reproduce

The following is the minimal code that caused the issue:

class MyClass
  def my_method
    foo = Foo.create()

    render json: foo
  end
end

This definitely is partially caused by an interaction with the SaveBang cop. If I disable that cop, I get no error with the above code. Additionally if I remove the json: part of the render call I get no error. Or if I leave SaveBang enabled but change create to create! I get no error.

RuboCop version

0.48.1 (using Parser 2.4.0.0, running on ruby 2.4.0 x86_64-darwin16)