How would you like to tag functions or things with properties (like the "return value must be used" property?
This less applies to something needing to be "used" as much as something needing to have an action taken in a `defer` like `.Close()` etc.
There's no reason the directive couldn't be compatible with Godoc either?
The only argument I can see is that it's a "slippery slope", but that's a pretty tired argument, you can use it against most any sort of progress in a language.
This seems a bigger ask than what's upthread and than what's necessary in most cases. You just need to make sure the return value is not implicitly discarded. Go linters already do this for `error`.
I have used both __checkReturn and __attribute__ ((warn_unused_result)) in C projects before and both were helpful, easy to reason about when the warning occurred, easy to work-around in the rare cases I really truly did want to drop the result (in Go `_ = ...` is already idiomatic), and useful in semantically varied cases (resource allocation, error handling, pure functions).