feat(lex,parse): Add stub try/catch implementation #195

lvcabral · 2023-11-29T19:55:16Z

Implementing try/catch/throw takes a good bit of work in the interpreter, so I'm splitting that into two pull requests. This one includes parsing try/catch/end try (without throw), and always executes only the try block to maintain backwards compatibility. It's a weird partial state, but the alternative is a massive pull request that can't be reasonably reviewed or understood.

see sjbarag/brs#554

Throwing exceptions and catching them aren't yet supported in `brs`, so executing only the `try` block seems to be a reasonable "bare minimum" approach to try/catch support. Handle `try`, `catch`, and `end try` lexemes in the parser, emitting TryCatch statements for the interpreter to execute naively. see sjbarag/brs#554#554

RBI 9.4 adds support for error handling via the `try`/`catch` model [1]. Interestingly, `try`, `catch`, and `endtry` are all valid identifiers! That makes parsing a little bit tougher, but it's not unprecedented in this language. Detect `try`/`catch`/throw`/`end try` during lexing and emit the proper lexemes. [1] https://developer.roku.com/docs/references/brightscript/language/error-handling.html see sjbarag/brs#554