Reduce per-token grouping primitive work

[alexander-beedie]

Per-token grouping optimisation/streamlining:

• Token.__init__ resolved is_keyword, is_whitespace, and is_newline with three ttype tests per token built; these flags are now snapshotted per ttype.

• token_next_by() built a fresh lambda per call for _token_matching(), two Python calls per token visited; now scans directly.

• group_functions() upper-cased each token once per keyword compared against, rather than once per token.

Results

• From cProfile, one parse of the 70.3 kB analytics payload:

  | frame                                    | master                 | this branch            |
  |------------------------------------------|------------------------|------------------------|
  | _TokenType.__contains__                  | 305,465 calls, 0.035 s | 180,437 calls, 0.022 s |
  | Token.__init__                           | 41,676 calls, 0.015 s  | 41,676 calls, 0.008 s  |
  | token_next_by + lambda + _token_matching | 0.088 s                | 0.040 s                |
  

• All 15 benchmark vectors improve; varies between 1.01x to 1.14x faster, with an overall mean speedup of ~1.08x.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.20%. Comparing base (111b35c) to head (fbb665d).
⚠️ Report is 25 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #880      +/-   ##
==========================================
+ Coverage   97.13%   97.20%   +0.07%     
==========================================
  Files          31       31              
  Lines        3663     3799     +136     
  Branches      328      347      +19     
==========================================
+ Hits         3558     3693     +135     
- Misses         63       65       +2     
+ Partials       42       41       -1     

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