Fix memory leak when ParsingError

[ksss]

I have discovered that a memory leak occurs when a ParsingError happens. This can occur in the following methods.

• RBS::Parser.parse_type
• RBS::Parser.parse_method_type
• RBS::Parser.parse_signature

If a global exit occurs before free_parser is called, free_parser may not be called at all.

I have fixed this issue by using rb_ensure to ensure that free_parser is called under all circumstances.

$ cat ensure.rb
#! /usr/bin/env ruby

require 'rbs'

Thread.new {
  while true
    mem = `ps -o rss= -p #{Process.pid}`.to_i
    puts mem
    sleep 1
  end
}

while true
  begin
    RBS::Parser.parse_signature("c")
  rescue RBS::ParsingError
  end
end

# before
$ bundle exec ruby -I lib ensure.rb
37200
230096
421920
614544
806752
995488
1185664
1376944
1567616
1755488

# after
$ bundle exec ruby -I lib ensure.rb
33024
33152
33152
33184
33280
33328
33328

[soutaro]

💯