quote-problems.md

Current

error: only the main function can be tagged with #[foob]
  --> tests/hello.rs:45:1
   |
45 | fn hello() {
   | ^^
error: aborting due to previous error
error: Could not compile `runtime`.
To learn more, run the command again with --verbose.                                                                                                                   [runtime:1]

Expected

error: only the main function can be tagged with #[foob]
  --> tests/hello.rs:45:1
   | 
44 | #[my_tag]
45 | fn hello() {
   | ^^
error: aborting due to previous error
error: Could not compile `runtime`.
To learn more, run the command again with --verbose.                                                                                                                   [runtime:1]

quote-problems.rs

  let name = &input.ident;

  if name != "main" {
    let tokens = quote_spanned! { name.span() =>
      compile_error!("only the main function can be tagged with #[foob]");
    };
    return proc_macro::TokenStream::from(tokens);
  }