Metastatic - a MetaAST for Elixir, Erlang and technically every language

mudasobwa

Creator of Cure

Metastatic is a library that provides a unified MetaAST (Meta-level Abstract Syntax Tree) intermediate representation for parsing, transforming, and analyzing code across multiple programming languages using a three-layer meta-model architecture.

“Build tools once, apply them everywhere,” they Java-evangelists said. I tried my own path to create a universal meta-model for program syntax that enables cross-language code analysis, transformation, and tooling.

Metastatic provides the foundation for that—the MetaAST meta-model and language adapters. Tools that leverage this foundation (mutation testing, purity analysis, complexity metrics) are built separately.

It’s already used in Ragex v0.19.0 — Documentation , https://cure-lang.org, and some WIP pets.

Now it’s probably a good time to release it to the wild.

iex|🌢|1 ▶ Metastatic.quote("defmodule M, do: def forty_two, do: 42", :elixir)

{:ok,
 {:container,
  [container_type: :module, name: "M", module: "M", language: :elixir, line: 1],
  [
    {:function_def,
     [
       name: "forty_two",
       params: [],
       visibility: :public,
       arity: 0,
       function: "forty_two",
       language: :elixir,
       line: 1
     ], [{:literal, [subtype: :integer], 42}]}
  ]}}

▸ Metastatic v0.23.0 — Documentation

https://github.com/oeditus/metastatic

14 comments

#library #ast #analysis #linter

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2026-09-03 10:19:02 UTC

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Asd

How does it compare to TreeSitter ASTs?

Post #1

mudasobwa

Creator of Cure

It does not compare to TreeSitter, if I put it straight.

TreeSitter does not build AST, in the first place. It builds CST (for concrete syntax tree.)

TreeSitter aims to build CST for each language based on its grammar, AFAIK. MetaAST is claimed to be the same for all the languages.

Post #2

dimitarvp

Wait until the Java devs find you with the pitchforks and torches for daring not to use “class” but “module” instead.

Post #3

mudasobwa

Creator of Cure

They’ll find {:container, [container_type: :class … there. I write all my code in an assumption there are many violent java-coders knowing where I live.

Post #4

Asd

CST is an AST with information about location of every node. The only meaningful difference between Metastatic and TreeSitter trees is that Metastatic has aliases like container, function_def, etc. and TreeSitter parses into more precise things like class, module, etc. Aside from that, these are similar trees

Post #5

dimitarvp

Lately I had some more dealings with TreeSitter. It can produce quite different trees depending on the language and the parser. It’s a pretty good and even revolutionary piece of software but it definitely can be better. Almost no structure is enforced. Compare what a Rust and Elixir program yield and you might get a little bit horrified.

Post #6

mudasobwa

Creator of Cure

Of course. TreeSitter has never been about generalization nor about building a language-agnostic tree.

Metastatic was designed strictly for that.

Post #7

mudasobwa

Creator of Cure

If you say so.

Post #8

mudasobwa

Creator of Cure

v0.22.0 All the analysis-related stuff has been extracted to MetaCredo. Metastatic remains a pure MetaAST handling.

Post #9

DaAnalyst

they also love ifs more than anything else (especially the 5+ times nested ones starting closer to the right side of the editor window given their default 4 char indentations), so you better take special measures of precaution!

Post #10

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