[kokosabu]

Summary

The two paren-based typescriptArrowFuncDef patterns in
syntax/ts-common/function.vim contain a nested quantifier:

/(\%(\_[^()]\+\|(\_[^()]*)\)*)\_s*=>/
start=/(\%(\_[^()]\+\|(\_[^()]*)\)*):/

\%(\_[^()]\+\|...\)* is the classic (a+)* shape. When the pattern fails
(a parenthesized call argument list that is not followed by => / ):), the
backtracking engine tries every way to split the run of non-paren characters,
so matching time doubles with each extra character. This PR drops the inner
\+. The alternation still matches exactly the same strings, but the
backtracking becomes linear.

Related: #135 (same symptom, same shape of reproducer).

Reproduction

Vim with regexpengine=1 (this is the default of the Vim bundled with macOS,
see vim/vim#18782), no vimrc:

const outputDir = cond
  ? ''
  : path.join(this.options.cwd, options.output)

vim -u NONE -N --cmd 'set re=1' --cmd 'syntax on' repro.ts

Vim hangs and eventually reports 'redrawtime' exceeded, syntax highlighting disabled. The time roughly doubles per character inside the parens
(0.78s -> 2.6s -> 10.6s on macOS Vim 9.1 as the argument list grows by two
characters per step).

Verification

Built Vim from master (9.2, patches 1-1143) with its own runtime, ran
synID() over every line of the reproducer and of a ~490-line TypeScript file:

engine	before	after
re=0	ok	ok
re=1	hang (> 6s, killed)	ok (< 6s)
re=2	ok	ok

Highlighting is unchanged: I dumped synstack() names for every character
position (14,543 positions, including 116 inside typescriptArrowFuncDef from
arrow functions with typed params, defaults, nested parens, generics and
arrow functions inside ternaries / call arguments). The dumps before and after
the change are identical (diff shows no differences).

The test suite that CI runs (Vader! syntax.vader tsx.vader in test/)
passes locally with this change: 149/149 (457 assertions) on macOS Vim 9.1.
I have not run it on Neovim.

merged/ is regenerated with node merge.js. Its only changes are the same
two lines in each of the three files.

The same patterns also exist in Vim's
runtime/syntax/shared/typescriptcommon.vim, lines 1951 and 1956. I can send
the same change to vim/vim after this is merged.

🤖 Generated with Claude Code

[HerringtonDarkholme]

Thanks!

[Copilot]

Copilot review overview

🟢 Approval recommended

The regex transformation preserves the accepted language, removes ambiguous nested repetition, and is consistently propagated to generated files.

Review effort: Balanced
Findings: None

What changed in this PR

Removes exponential backtracking from TypeScript arrow-function syntax matching while preserving highlighting behavior.

Changes:

• Replaces nested quantified character runs with deterministic single-character repetition.
• Synchronizes all generated TypeScript syntax bundles.

File	Description
syntax/​ts-common/​function.vim	Optimizes both parenthesized arrow-function patterns.
merged/​typescriptreact.vim	Updates the generated TSX syntax bundle.
merged/​typescriptcommon.vim	Updates the generated common syntax bundle.
merged/​typescript.vim	Updates the generated TypeScript syntax bundle.

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[kokosabu]

Thanks for the quick merge! Sent the same change to Vim's runtime: vim/vim#21400