Rollup merge of #89046 - oli-obk:fix_oflo, r=estebank

"Fix" an overflow in byte position math

r? `@estebank`

help! I fixed the ICE only to brick the diagnostic.

I mean, it was wrong previously (using an already expanded macro span), but it is really bad now XD

compiler/rustc_errors/src/lib.rs

@@ -13,9 +13,11 @@
 #[macro_use]
 extern crate rustc_macros;
 
+#[macro_use]
+extern crate tracing;
+
 pub use emitter::ColorConfig;
 
-use tracing::debug;
 use Level::*;
 
 use emitter::{is_case_difference, Emitter, EmitterWriter};