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tree-sitter-scala 0.20.1

Hi everyone. On behalf of the tree-sitter-scala project, I am happy to announce tree-sitter-scala 0.20.1. The first two segment of the version number comes from the tree-sitter-cli that was used to generate the parser, and the last segment is our actual version number.

About tree-sitter-scala

tree-sitter-scala is a Scala parser in C language, generated using Tree-sitter CLI, and conforming to the Tree-sitter API. Tree-sitter parsers are generally fast, incremental, and robust (ok with partial errors).

Since its initial release in 2017, Tree-sitter parsers are adopted by editors like Atom, NeoVim, Emacs, and Helix to provide language features like syntax highlight and folding and more (supposedly part of


Full release note is at

Baseline smoke test

Previously, we’ve added smoke test that parses the *.scala source for Scala 2 library, Scala 2 compiler, and Scala 3 compiler.

tree-sitter-scala scala-library scalac Dotty
0.20.0 89% 68% 66%
Note: We thought scala-library parsing % was 100%, but we found out it wasn’t parsing all the files.

Since then we’ve updated smoke test to use Scala 3.3.0 code base. @sideeffffect also contributed adding the syntax complexity check against the parser generation time regression.

Parsing improvements

Parsing % for Scala 2 library, Scala 2 compiler, and Scala 3 compiler respective are as follows.

tree-sitter-scala scala-library scalac Dotty
0.20.1 98% 93% 83%
0.20.0 89% 68% 66%

Here are the fixes that contributed to this jump:

Rust and Swift bindings

tree-sitter-scala 0.20.1 is published to, as well as 0.20.0, which was back published. This allows easier consumption of the parser using Rust.

Swift bindings and Swift Package Manager (SPM) support were contributed by @mattmassicotte in #234.

Parser optimization

In addition to enhancements, susliko has contributed parser optimizations as well.

The parser complexity had crept up a bit to take a few minutes, and the latter in particular, halves the maximum grammar state to 1300 and reduces the parser generation time to 10s:

$ time node_modules/.bin/tree-sitter generate
node_modules/.bin/tree-sitter generate  9.24s user 0.41s system 99% cpu 9.664 total


tree-sitter-scala 0.20.1 was brought to you by 6 contributors and a good bot:

$ git shortlog -sn --no-merges v0.20.0...
    26  susliko
    21  Eugene Yokota
    12  GitHub
     6  Ondra Pelech
     1  Domas Poliakas
     1  Kasper Kondzielski
     1  Matt Massicotte

Thanks to everyone who’s helped improve tree-sitter-scala by using them, reporting bugs, improving our documentation, and submitting and reviewing pull requests.

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