An error occurs when using an one-liner (in) pattern matching

[koic]

This is a valid syntax from Ruby 3.1.

Ruby 3.0

Both operands are hash literal:

% ruby -e '{key: :value} in key: value; p value'
ruby 3.0.4p208 (2022-04-12 revision 3fa771dded) [x86_64-darwin19]
-e:1: syntax error, unexpected label
{key: :value} in key: value; p value

Ruby 3.1

Ditto:

% ruby -ve '{key: :value} in key: value; p value'
ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [x86_64-darwin19]
:value

But the parser gem raises the following error:

% ruby-parse -e '{key: :value} in key: value'
Failed on: (fragment:0)
/Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/variables_stack.rb:32:in `declared?': undefined method `include?' for nil:NilClass (NoMethodError)

      @stack.last.include?(name.to_sym)
                 ^^^^^^^^^
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/builders/default.rb:1830:in `check_duplicate_pattern_key'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/builders/default.rb:1640:in `match_pair'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/ruby31.rb:7109:in `_reduce_518'
        from (eval):3:in `_racc_do_parse_c'
        from (eval):3:in `do_parse'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/base.rb:190:in `parse'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner/ruby_parse.rb:141:in `process'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:254:in `process_buffer'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:231:in `block in process_fragments'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:225:in `each'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:225:in `each_with_index'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:225:in `process_fragments'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:215:in `block in process_all_input'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/3.1.0/benchmark.rb:296:in `measure'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:214:in `process_all_input'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner/ruby_parse.rb:137:in `process_all_input'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:35:in `execute'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/lib/parser/runner.rb:13:in `go'
        from /Users/koic/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/parser-3.1.2.0/bin/ruby-parse:7:in `<top (required)>'
        from /Users/koic/.rbenv/versions/3.1.2/bin/ruby-parse:25:in `load'
        from /Users/koic/.rbenv/versions/3.1.2/bin/ruby-parse:25:in `<main>'

cf. rubocop/rubocop#10773