Avoid string allocations when generating object name

[ghost]

Description

Hi, I am trying to optimize YARD a bit to speed up documentation runs on a large codebase.

The codebase is private, so I am using https://github.com/watir/watir/ as a smaller stand-in to report benchmarking numbers from https://github.com/SamSaffron/memory_profiler.

Test set-up

• Ruby 2.7.6 (installed via rvm on Linux)
• Watir version: 293bed2b57c
• MemoryProfiler version: 1.0.0
• YARD baseline: 0a55093
• Test command:
  • ruby-memory-profiler --no-color --retained-strings=500 --allocated-strings=500 --max=300 -o prof.log ./run-yard.rb stats
    • run-yard.rb is a smaller version of /bin/yard (MemoryProfiler was not able to run /bin/yard)
    • I am using the stats command to avoid memory exhaustion

Performance data

• Before
  • Total allocated: 187901758 bytes (1987572 objects)
  • Total retained: 4052113 bytes (53463 objects)
• After
  • Total allocated: 187459865 bytes (1976523 objects)
  • Total retained: 4052153 bytes (53464 objects)
• Savings
  • Total allocated: 441893 bytes (11049 objects)
  • Total retained: -40 bytes (-1 object)

Completed Tasks

• I have read the Contributing Guide.
• The pull request is complete (implemented / written).
• Git commits have been cleaned up (squash WIP / revert commits).
• I wrote tests and ran bundle exec rake locally (if code is attached to PR).

[lsegal]

Thanks for this improvement!