Add true and false as reserved words

[pushkine]

Did not test it, but based on the discussion on #392 and #405 this should fix #655

[codecov]

Codecov Report

Merging #656 (d4ac363) into main (01ed0ce) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #656      +/-   ##
==========================================
- Coverage   82.65%   82.58%   -0.08%     
==========================================
  Files          56       56              
  Lines        5928     5690     -238     
  Branches     1344     1344              
==========================================
- Hits         4900     4699     -201     
+ Misses        745      708      -37     
  Partials      283      283              

Impacted Files	Coverage Δ
src/util/isIdentifier.ts	100.00% <ø> (ø)
src/Options-gen-types.ts	75.00% <0.00%> (-25.00%)	⬇️
src/parser/index.ts	77.77% <0.00%> (-7.94%)	⬇️
src/computeSourceMap.ts	83.33% <0.00%> (-5.56%)	⬇️
src/util/getNonTypeIdentifiers.ts	94.44% <0.00%> (-5.56%)	⬇️
src/parser/plugins/types.ts	91.66% <0.00%> (-3.34%)	⬇️
src/parser/tokenizer/readWord.ts	82.35% <0.00%> (-3.02%)	⬇️
src/parser/traverser/util.ts	83.33% <0.00%> (-2.95%)	⬇️
src/parser/traverser/base.ts	95.45% <0.00%> (-1.69%)	⬇️
src/parser/traverser/statement.ts	82.16% <0.00%> (-0.44%)	⬇️
... and 20 more

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[github-actions]

Benchmark results

Before this PR: 283.7 thousand lines per second
After this PR: 283.8 thousand lines per second

Measured change: 0.04% faster (2.04% slower to 4.49% faster)
Summary: Likely no significant difference

[alangpierce]

Thanks for the bug report and the fix! Agreed that this fixes the issue, and I just tested to confirm.

I was trying to figure out how I originally missed this case, and I see from MDN https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar
this detail:

Additionally, the literals null, true, and false cannot be used as identifiers in ECMAScript.

So I guess those are not technically "keywords" but they're not allowed as identifiers either, so they should be in the list here.

There are a few more things that would be nice here:

• Add a test
• Add null as well
• Document these three in a new section of the RESERVED_WORDS declaration
• Maybe add a jsdoc comment for the isIdentifier function

But I'd be happy to do those as a quick follow-up PR.

[alangpierce]

Published as 3.20.3.