Use smol_str for Identifier

[MichaReiser]

One more time. Trying to use smol_str for Identifiers to avoid heap allocations for strings shorter than 24 characters.

I also expect this to help with red_knot where the symbol table can't store string slices for symbol names. Instead, the symbol table clones the identifier name which is O(1) for smol_str.

Edit: It should be possible to store a &Name in the symbol table, now that salsa supports the &'db lifetime. That means, O(1) cloning is not as important anymore.

Performance improvement

I think the performance improvement mainly comes from the removed Box<str> to String conversion in the hot parse_name function. It would be possible to remove that conversion by changing ExprName to store a Box<str>.

For a comparison, #12100 uses a Box<str> instead of a SmolStr. The parser improvements are not as significant. But no linter benchmark regress.

General observation:

• Parsing becomes faster because of the removed cloning of the ExprName identifier
• I assume lexing becomes faster because it can bypass the heap allocation for most names
• Speedup in AST drop
• Some linter benchmarks become slower. I assume it is because dereferencing a Name now requires branching

[codspeed-hq]

CodSpeed Performance Report

Merging #12099 will improve performances by 6.89%

_{Comparing smol_str (c157032) with main (d107968)}

Summary

⚡ 1 improvements
✅ 29 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	smol_str	Change
⚡	linter/default-rules[pydantic/types.py]	1.9 ms	1.8 ms	+6.89%

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check encountered linter errors. (no lint changes; 1 project error)

demisto/content (error)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview

warning: The top-level linter settings are deprecated in favour of their counterparts in the `lint` section. Please update the following options in `pyproject.toml`:
  - 'ignore' -> 'lint.ignore'
  - 'select' -> 'lint.select'
  - 'unfixable' -> 'lint.unfixable'
  - 'per-file-ignores' -> 'lint.per-file-ignores'
warning: `PGH001` has been remapped to `S307`.
warning: `PGH002` has been remapped to `G010`.
warning: `PLR1701` has been remapped to `SIM101`.
ruff failed
  Cause: Selection of deprecated rule `E999` is not allowed when preview is enabled.

Formatter (stable)

ℹ️ ecosystem check encountered format errors. (no format changes; 1 project error)

openai/openai-cookbook (error)

warning: Detected debug build without --no-cache.
error: Failed to parse examples/gpt_actions_library/.gpt_action_getting_started.ipynb:11:1:1: Expected an expression
error: Failed to parse examples/gpt_actions_library/gpt_action_bigquery.ipynb:13:1:1: Expected an expression

Formatter (preview)

ℹ️ ecosystem check encountered format errors. (no format changes; 2 project errors)

demisto/content (error)

ruff format --preview --exclude Packs/ThreatQ/Integrations/ThreatQ/ThreatQ.py

warning: The top-level linter settings are deprecated in favour of their counterparts in the `lint` section. Please update the following options in `pyproject.toml`:
  - 'ignore' -> 'lint.ignore'
  - 'select' -> 'lint.select'
  - 'unfixable' -> 'lint.unfixable'
  - 'per-file-ignores' -> 'lint.per-file-ignores'
warning: `PGH001` has been remapped to `S307`.
warning: `PGH002` has been remapped to `G010`.
warning: `PLR1701` has been remapped to `SIM101`.
ruff failed
  Cause: Selection of deprecated rule `E999` is not allowed when preview is enabled.

openai/openai-cookbook (error)

ruff format --preview

warning: Detected debug build without --no-cache.
error: Failed to parse examples/gpt_actions_library/.gpt_action_getting_started.ipynb:11:1:1: Expected an expression
error: Failed to parse examples/gpt_actions_library/gpt_action_bigquery.ipynb:13:1:1: Expected an expression

[MichaReiser]

Closing in favor of #12101 which shows the most promising results.