#[stable], #[unstable], #[deprecated] are not errors when used non-#[staged_api] crates

[huonw]

They are ignored, but silently. It is probably better if we make them errors to give us room to build some future system with those nice names.

This compiles without a peep from rustc:

#![allow(dead_code)]

#[stable]
fn foo() {}
#[deprecated] 
struct Bar;
#[unstable]
type X = i8;

fn main() {}

[nagisa]

Willing to pick this up.

One thing to note, that it will 100% cause breakage outside the compiler, and possibly inside as well.

[brson]

I did it this way to avoid breakage for people who were using them. We might put in deprecation warnings for a few weeks.

[huonw]

I'm in favour of a smooth deprecation path via warnings! :)

[pnkfelix]

@alexcrichton asks whether the unused-attribute lint would catch these, or if they are unconditonally marked as used.

Either way, some sort of warning sounds good.

[pnkfelix]

1.0 polish, P-high.

[sfackler]

@pnkfelix they are unconditionally marked as used.

[brson]

Ugh, I'm wishing I had done this a lot sooner. Working on a patch for this now, but it's probably going to cause some breakage. I'll see if I can guess how much.

[brson]

Here's the list of current out-of-tree usage of stability attributes https://gist.github.com/brson/1dd62761ee8dff6cdcaa

[alexcrichton]

This was fixed and backported to beta recently, yay!