```ruby
# frozen_string_literal: true
module Reek
  module AST
    #
    # Locates references to the current object within a portion
    # of an abstract syntax tree.
    #
    class ReferenceCollector
      STOP_NODES = [:class, :module, :def, :defs].freeze

      def initialize(ast)
        @ast = ast
      end

      def num_refs_to_self
        (explicit_self_calls + implicit_self_calls).size
      end

      private

      attr_reader :ast

      def explicit_self_calls
        [:self, :super, :zsuper, :ivar, :ivasgn].flat_map do |node_type|
          ast.each_node(node_type, STOP_NODES)
        end
      end

      def implicit_self_calls
        ast.each_node(:send, STOP_NODES).reject(&:receiver)
      end
    end
  end
end
```

Remove completely untested stop nodes list
user
```ruby
# frozen_string_literal: true
module Reek
  module AST
    #
    # Locates references to the current object within a portion
    # of an abstract syntax tree.
    #
    class ReferenceCollector
      def initialize(ast)
        @ast = ast
      end

      def num_refs_to_self
        (explicit_self_calls + implicit_self_calls).size
      end

      private

      attr_reader :ast

      def explicit_self_calls
        [:self, :super, :zsuper, :ivar, :ivasgn].flat_map do |node_type|
          ast.each_node(node_type)
        end
      end

      def implicit_self_calls
        ast.each_node(:send).reject(&:receiver)
      end
    end
  end
end
```
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