- If you want to contribute to a large open source project, many of the error message bugs are simple enough to let you focus on that.
- If you want to learn to write concise, correct Typescript types, look at the standard library/DOM bugs. The DOM bugs, especially, are in a smaller repo with less building overhead.
- If you want to learn about compilers, the parser bugs are a good place to start, mostly because it's easier to figure out what the parser should be doing.
- If you want something interactive, take a look at the codefix bugs. They tend to be complicated to test, but it's super cool when you see your changes running in an editor. (The intellisense, formatter and smart select bugs are similar.)
These bugs range from fixing message grammar, splitting one error into several, up to restructuring code to be able to give more detailed errors.