proc-macro applied with `cfg_attr` doesn’t see associated attributes

[b8591340]

#[cfg_attr(debug_assertions, derive(EnumKind), enum_kind(Kind, repr(u32)))]

#[macro_use]
extern crate enum_kinds;

#[cfg_attr(debug_assertions, derive(EnumKind), enum_kind(ValueId, repr(u32)))]
enum Value {
    A,
    B,
}

proc macro returned error: proc-macro panicked:
#[derive(EnumKind)] requires an associated `enum_kind` attribute to be specified

rustc 1.56.0-nightly (2f662b140 2021-08-29)

cargo check works, it builds correctly both in debug and release profiles.

[jonas-schievink]

This is where our attribute processing during name resolution breaks down. The expected macro input is (I think):

#[enum_kind(ValueId, repr(u32))]
enum Value {
    A,
    B,
}

When we strip the #[derive], we end up removing the entire containing attribute.

[wyatt-herkamp]

#16789 will partly fix this.
if the syntax is like

#[cfg_attr(debug_assertions, derive(EnumKind))]
#[cfg_attr(debug_assertions, enum_kind(ValueId, repr(u32)))]
enum Value {
    A,
    B,
}

However, if you combine the two attributes together it will continue to error out.

I can fix this after #16789 merges.