pub fn error_spanned_by<A: ToTokens, T: Display>(&self, obj: A, msg: T) {
            self.errors
                .borrow_mut()
                .as_mut()
                .unwrap()
                // Curb monomorphization from generating too many identical methods.
                .push(syn::Error::new_spanned(obj.into_token_stream(), msg));
        }
Add an error to the context object with a tokenenizable object.

The object is used for spanning in error messages.
esp-hal-procmacros/src/embassy.rs