miniblog.

Playing with optional type signatures in Python, I realise that the return type is the most important to me. I'd much rather have a function with only a return type instead of a function with only parameter types. It's often quick to add too.

I'm working on arity errors in Garden, my toy programming language. Rather than just saying "expected 3, got 4 arguments", I'm trying to report where the extra argument is, or what extra argument was expected.

Counter-intuitively, if you're writing a parser for a programming language, you need it to be a total function. As soon as you build IDE tooling, you need ASTs from invalid or incomplete input. The parser should return (Ast, List<Error>) rather than Result<Ast, Error>.