[bPspGiJT8Y]

> Because possibly you return the partial assuming it's a number, and try to use it somewhere else, possibly even in another file.

Sorry, I must've been more explicit instead of implying certain usage patterns. What I meant here is that I have a hard time imagining this happening because I would start working on a function by writing its type signature. Unless my types check out, I won't be able to mark this function as "done" and jump to another part of code. So the situation "you return the partial assuming it's a number" simply can not happen, that's exactly what type checking is for. By the time I use it in another place, it has to already have been type checked.

[kerkeslager]

Sure, but that usage pattern is not without cost. You're basically eschewing relying on type inference across function boundaries.

I think writing out type signatures is The Right Way, but it does take time, and The Right Way doesn't always happen on complicated projects with close deadlines.