Fun blog post on implementing a small programming language, including a tiny and readable type checker!
https://blog.mgechev.com/2017/08/05/typed-lambda-calculus-create-type-checker-transpiler-compiler-javascript/
Related Posts
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
I'm designing a programming language and trying to decide the type of `let x = 1;`. Should it be Unit or Int?
Advantage of Int: really convenient when evaluating snippets in a REPL.
Advantage of Unit: It's much less confusing when type inference runs on an incomplete function.