expected suffix token in proc macro

[Mark-Simulacrum]

Picked up by the beta crater run

• https://crater-reports.s3.amazonaws.com/beta-1.46-rustdoc-1/beta-2020-07-24/gh/retro486.task-progress/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.46-1/beta-2020-07-24/reg/woff2-sys-0.0.1/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.46-1/beta-2020-07-24/reg/static_map_macros-0.2.0-beta/log.txt

I've not attempted to reproduce these locally, but they don't look spurious.

[Mark-Simulacrum]

cc @petrochenkov proc macros / parser / resolution

[petrochenkov]

The first two regressions are known from #73345 (comment), older versions of cpp-macros relied on some incorrect pretty-printing from rustc.

Not sure about the third regression, perhaps @Aaron1011 has seen it in one of the other expansion-related PRs.

[Aaron1011]

The static_map_macros regressions is also due to pretty-printing changes:

https://github.com/cbreeden/static-map/blob/14cada499fcbdeacf0735775978320f226876f8b/static_map_macros/src/lib.rs#L15-L25:

const LEADING: &str = "enum __StaticMap__ {\n    A =\n        static_map!(@ zero";
const TRAILING: &str = "),\n}";

fn trim(input: &str) -> &str {
    assert!(input.starts_with(LEADING));
    assert!(input.ends_with(TRAILING));

    let (_, input) = input.split_at(LEADING.len());
    let (input, _) = input.split_at(input.len() - TRAILING.len());
    input.trim()
}

Before/after:

enum __StaticMap__ {\n    A =\n        static_map!(@ zero
enum __StaticMap__\n{\n    A = static_map !\n    (@ zero

[spastorino]

Assigning P-medium as discussed as part of the Prioritization Working Group procedure and removing I-prioritize.