Misses special characters after bare # (e.g. /#(\d+)/)

[Tietew]

In ruby's regexp, /#(\d+)/ matches literal # then unnamed capture (\d+).
But Regexp::Parser.parse treats it as literal '#(\d+)'.

irb(main):001:0> /#(\d+)/.match('#123')
=> #<MatchData "#123" 1:"123">
irb(main):002:0> Regexp::Parser.parse('#(\d+)')
=> #<Regexp::Expression::Root:0x00005619a4ad5e30 @type=:expression, @token=:root, @text="", @ts=0, @level=nil, @set_level=nil, @conditional_level=nil, @nesting_level=0, @quantifier=nil, @options={}, @expressions=[#<Regexp::Expression::Literal:0x00005619a4b8cb80 @type=:literal, @token=:literal, @text="#(\\d+)", @ts=0, @level=0, @set_level=0, @conditional_level=0, @nesting_level=1, @quantifier=nil, @options={}>]>
irb(main):003:0> Regexp::Parser.parse('\#(\d+)')
=> #<Regexp::Expression::Root:0x00005619a4be42e0 @type=:expression, @token=:root, @text="", @ts=0, @level=nil, @set_level=nil, @conditional_level=nil, @nesting_level=0, @quantifier=nil, @options={}, @expressions=[#<Regexp::Expression::EscapeSequence::Literal:0x00005619a4bf5310 @type=:escape, @token=:literal, @text="\\#", @ts=0, @level=0, @set_level=0, @conditional_level=0, @nesting_level=1, @quantifier=nil, @options={}>, #<Regexp::Expression::Group::Capture:0x00005619a4bf52c0 @type=:group, @token=:capture, @text="(", @ts=2, @level=0, @set_level=0, @conditional_level=0, @nesting_level=1, @quantifier=nil, @options={}, @expressions=[#<Regexp::Expression::CharacterType::Digit:0x00005619a4bf51d0 @type=:type, @token=:digit, @text="\\d", @ts=3, @level=1, @set_level=0, @conditional_level=0, @nesting_level=2, @quantifier=#<Regexp::Expression::Quantifier:0x00005619a4bf51a8 @token=:one_or_more, @text="+", @mode=:greedy, @min=1, @max=-1>, @options={}>], @number=1, @number_at_level=1>]>

Regexp::Parser.parse('#(\d+)') shoud return same tree as Regexp::Parser.parse('\#(\d+)') (except for first node, it's "#" instead of "\\#")

[Tietew]

Same issue on #[abc] (character class), #(?...) (non-capture grouping), #\1 (backref), #@! (invalid instance vars), #@@! (invalid class vars), #^ (sol anchor, useless but legal), #$ (eol anchor), #\z (eos anchor), etc.

[jaynetics]

@Tietew i've just released version 1.8.1 with a fix. thank you very much for the detailed report!