Future of StatusCode::as_str

I wanted to write-up some thoughts on the future direction for the StatusCode::as_str method. The as_str method returns the numeric part of the status code as a string slice. So, StatusCode::OK.as_str() returns "200", and StatusCode::NOT_FOUND.as_str() returns "404", and so forth. This works for all StatusCodes, from 100-999. Since the StatusCode only stores an integer, there's no field to actually borrow the string from, so it is in reality returning a &'static str, even though the method signature doesn't expose that.

There have been several PRs filed to make that part of the signature (that is, change from fn as_str(&self) -> &str to fn as_str(&self) -> &'static str) (#380 #436 #466).

I've personally questioned the value of the method in it's entirety:

I was thinking that perhaps we just axe StatusCode::as_str, because really, how useful can it be? There's the Display impl to get a string, and if you want a fast path for some common status codes, a user can just do that manually (hyper has a fast path for HTTP/1.1 200 OK, for instance).

That comment was prompted as I wondered about the cost of including all the static strings in the binary, when certainly most applications will never need them. Because I don't see value in the method, I've held off from changing it return a &'static str. Instead, I've thought we may just want to deprecate it and chop it for 1.0.

However, I realize I could be wrong, and not considering a large use case for this method. If so, we can just merge one of the PRs and carry on. If I have overlooked something, hopefully we can collect the reasons why to keep the method, with some details about the value it provides versus the cost of having a bunch of extra strings in the binary for everyone.

Start with the StatusCode::as_str method and read the referenced PRs #380, #436, and #466, along with the linked discussion on #443. Compare the arguments for retaining, changing, deprecating, or removing the method, including its binary-size cost; done means the project has an agreed direction and an actionable follow-up.