panic: "compiler/fallback mismatch" when using proc_macro2::fallback::force() escape hatch

[sam0x17]

panic: "compiler/fallback mismatch" when using proc_macro2::fallback::force() escape hatch

[sam0x17]

Just circling back on this. Is there any more context information you'd like me to provide @dtolnay?

[dtolnay]

Arbitrarily intermixing fallback tokens and compiler tokens is not supported / not meaningful. Tokens that you create during fallback need to be accessed only during fallback and vice versa. So something like:

proc_macro2::fallback::force();
let source_text = item.span().source_text();
proc_macro2::fallback::unforce();
let Some(excerpt) = source_text else {
    return Err(Error::new(Span::call_site(), "..."));
};