Bug: edge case slow highlighting performance

[thenbe]

The following two files are exactly the same except for a single character. Despite that, opening good.nix is 6+ times faster than opening repro.nix.

$ hyperfine -N --ignore-failure "nvim good.nix -c exit" "nvim repro.nix -c exit"
Benchmark 1: nvim good.nix -c exit
  Time (mean ± σ):     174.9 ms ±   5.4 ms    [User: 138.0 ms, System: 44.0 ms]
  Range (min … max):   167.8 ms … 185.5 ms    16 runs

Benchmark 2: nvim repro.nix -c exit
  Time (mean ± σ):      1.192 s ±  0.110 s    [User: 0.506 s, System: 0.687 s]
  Range (min … max):    1.006 s …  1.321 s    10 runs

Summary
  nvim good.nix -c exit ran
    6.81 ± 0.66 times faster than nvim repro.nix -c exit

Minimal repro

1. Create file good.nix:

   myFunc {
     preCheck = "hello";
     disabledTests = [
       # Lllllll aaaaaaa aaaa aaa `bar`
       ""
     ];
   }
   

2. Create file repro.nix (identical to first file except for one character)

   myFunc {
     preCheck = "hello";
     disabledTests = [
       # Lllllll aaaaaaa aaaa aaa `bar`
       "f"
     ];
   }
   

3. Observe that opening repro.nix is very slow, especially when compared to opening good.nix

Version

NVIM v0.10.0-dev-3a34743
Build type: Release
LuaJIT 2.1.1693350652

nvim-treesitter: bf982eb