Expose proc_macro's before() and after() methods on Span

[dtolnay]

Tracking issue: rust-lang/rust#87552

[huybuidac]

hey @dtolnay , it causes "unknown feature proc_macro_span_shrink", what should I do?

[BestRamsay]

@dtolnay, How i can resolve error[E0635]: unknown feature proc_macro_span_shrink ??

[taiki-e]

@huybuidac @BestRamsay: I think you need to upgrade the nightly toolchain to nightly-2021-10-11 or later, downgrade proc-macro2 to 1.0.43, or use a non-nightly toolchain.

[adamhfox]

@taiki-e any other potential solutions seems to cause more errors for me

[taiki-e]

@adamhfox: Since none of you provided specific information about the project where the error occurred, I talked about the basic case.
That said, I would be surprised if downgrading proc-macro2 (cargo update -p proc-macro2 --precise 1.0.43) does not work.

[adamhfox]

cargo update -p proc-macro2 --precise 1.0.43

Thank you, that solved it

The problem arised for me when creating a new anchor project