Regression in v2: flag constants no longer appear in cargo doc output

[nicholasbishop]

Steps to reproduce:

cargo new --lib bitflags-missing-docs
cd bitflags-missing-docs
cargo add bitflags

Replace src/lib.rs with:

bitflags::bitflags! {
    pub struct Flags: u32 {
        /// Hello.
        const HELLO = 1;
    }
}

Run cargo doc --open and search for "hello". It doesn't find anything of that name, and if you go to the Flags page it indeed has no documented constants.

If you change Cargo.toml to use bitflags = "1" and re-run cargo doc, the constant is there as expected:

[nicholasbishop]

I think this is due to #282, as demonstrated with this example:

pub struct A;
pub struct B;

impl A {
    pub const VAL: u32 = 0;
}

const _: () = {
    impl B {
        pub const VAL: u32 = 0;
    }
};

pub const B2: u32 = B::VAL;

Running cargo doc on that shows A::VAL but not B::VAL.

[KodrAus]

This issue is fixed upstream, but won't make it to a stable release until April 20th so it might be worth us mitigating it here anyways. It should be fairly straightforward. We can split the impl block that defines those constants from the one that implements other methods and move the constants to outside the const _: () { .. } block.

[nicholasbishop]

Thanks for the fix :)