See https://github.com/lsegal/yard/issues/487

yard-binary-operator.rb

module YARD
  module Templates::Helpers
    module HtmlHelper

      BINARY_OPERATORS = %w{ + - * / % ** << >> & | <= < > >= <=> == === =~ }.collect { |t| CGI.escapeHTML(t) }

      alias signature_pre_change_binary_operators signature
      def signature(*args)
        html = signature_pre_change_binary_operators(*args)
        if %r{\((.+?)\) <strong>(.+?)</strong>\((.+?)\)} =~ html and BINARY_OPERATORS.include? $2
          "%s(%s) &larr; self <strong>%s</strong> %s%s" % [$`, $1, $2, $3, $']
        else
          html
        end
      end
    end
  end
end