Explain why an untranslatable_diagnostic occurs

Author: bjorn3

compiler/rustc_interface/src/interface.rs

@@ -371,7 +371,6 @@ pub(crate) fn initialize_checked_jobserver(early_dcx: &EarlyDiagCtxt) {
 
 // JUSTIFICATION: before session exists, only config
 #[allow(rustc::bad_opt_access)]
-#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
 pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Send) -> R {
     trace!("run_compiler");
 
@@ -425,7 +424,11 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 config.opts.unstable_opts.translate_directionality_markers,
             ) {
                 Ok(bundle) => bundle,
-                Err(e) => early_dcx.early_fatal(format!("failed to load fluent bundle: {e}")),
+                Err(e) => {
+                    // We can't translate anything if we failed to load translations
+                    #[allow(rustc::untranslatable_diagnostic)]
+                    early_dcx.early_fatal(format!("failed to load fluent bundle: {e}"))
+                }
             };
 
             let mut locale_resources = config.locale_resources;