miniblog.

I'm having fun writing a simple type checker, but I'm learning firsthand why syntax-directed checking doesn't work. It prevents inference. My checker catches real bugs, but it can't handle cases like this: [1, 2].map(fun(x) { x + 1; }) I think I need bidirectional checking.

Really cute approach to reporting type errors: when there's a type error, show an example of a runtime error that the type check has prevented! Data-Driven Techniques for Type Error Diagnosis https://escholarship.org/uc/item/59s4h4pv

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.