My biggest gripe with inferred types is that you wind up with errors at random usage sites instead of at where the actual type “error” is. For example, with inferred return types you can wind up returning `a | b` when you thought you were returning `a` and this might actually be coincidentally fine for a bit until you use it somewhere that only takes `a` and you get a type mismatch. You can then trace backwards until you find the source of the bad assignment, which can be a few layers after a bit of inference, and this always felt antithetical to the improved ergonomics of types. As a result I always enforce explicit return type annotations with inference only within scopes. But TS happily supports a spectrum!