rust/CONTRIBUTING.md

The project is in its early stages: contributions are welcome and
would be **very** helpful, but the project is not *yet* optimized for
contribution. Moreover, it is doubly experimental, so there's no
guarantee that any work here would reach production. That said, here
are some areas where contributions would be **especially** welcome:


* Designing internal data structures: RFC only outlines the
  constraints, it's an open question how to satisfy them in the
  optimal way. See `ARCHITECTURE.md` for current design questions.

* Porting libsyntax parser to libsyntax2: currently libsyntax2 parses
  only a tiny subset of Rust. This should be fixed by porting parsing
  functions from libsyntax one by one. Take a look at the
  [libsyntax parser](https://github.com/rust-lang/rust/blob/6b99adeb11313197f409b4f7c4083c2ceca8a4fe/src/libsyntax/parse/parser.rs)
  for "what to port" and at the
  [Kotlin parser](https://github.com/JetBrains/kotlin/blob/4d951de616b20feca92f3e9cc9679b2de9e65195/compiler/frontend/src/org/jetbrains/kotlin/parsing/KotlinParsing.java)
  for "how to port".

* Writing validators: by design, libsyntax2 is very lax about the
  input. For example, the lexer happily accepts unclosed strings. The
  idea is that there should be a higher level visitor, which walks the
  syntax tree after parsing and produces all the warnings. Alas,
  there's no such visitor yet :( Would you like to write one? :)

* Creating tests: it would be tremendously helpful to read each of
  libsyntax and libsyntax2 parser functions and crate a small separate
  test cases to cover each and every edge case.

* Building stuff with libsyntax2: it would be really cool to compile
  libsyntax2 to WASM and add *client side* syntax validation to rust
  playground!


Do take a look at the issue tracker, and try to read other docs in
the [./docs](https://github.com/matklad/libsyntax2/tree/master/docs) folder!

If you don't know where to start, or have *any* questions or suggestions,
don't hesitate to chat at [Gitter](https://gitter.im/libsyntax2/Lobby)!