class RuboCop::Cop::Style::SymbolArray

def symbol_without_quote?(string)
  special_gvars = %w[
    $! $" $$ $& $' $* $+ $, $/ $; $: $. $< $= $> $? $@ $\\ $_ $` $~ $0
    $-0 $-F $-I $-K $-W $-a $-d $-i $-l $-p $-v $-w
  ]
  redefinable_operators = %w(
    | ^ & <=> == === =~ > >= < <= << >>
    + - * / % ** ~ +@ -@ [] []= ` ! != !~
  )
  # method name
  string =~ /\A[a-zA-Z_]\w*[!?]?\z/ ||
    # instance / class variable
    string =~ /\A\@\@?[a-zA-Z_]\w*\z/ ||
    # global variable
    string =~ /\A\$[1-9]\d*\z/ ||
    string =~ /\A\$[a-zA-Z_]\w*\z/ ||
    special_gvars.include?(string) ||
    redefinable_operators.include?(string)
end