rustc_expand: make a message translatable

Author: GrigorenkoPV

compiler/rustc_expand/messages.ftl

@@ -129,6 +129,9 @@ expand_module_multiple_candidates =
 expand_must_repeat_once =
     this must repeat at least once
 
+expand_non_inline_modules_in_proc_macro_input_are_unstable =
+    non-inline modules in proc macro input are unstable
+
 expand_not_a_meta_item =
     not a meta item
 

compiler/rustc_expand/src/expand.rs

@@ -39,6 +39,7 @@ use crate::errors::{
     RecursionLimitReached, RemoveExprNotSupported, RemoveNodeNotSupported, UnsupportedKeyValue,
     WrongFragmentKind,
 };
+use crate::fluent_generated;
 use crate::mbe::diagnostics::annotate_err_with_kind;
 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
 use crate::placeholders::{placeholder, PlaceholderExpander};
@@ -882,7 +883,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         }
 
         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
-            #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
             fn visit_item(&mut self, item: &'ast ast::Item) {
                 match &item.kind {
                     ItemKind::Mod(_, mod_kind)
@@ -892,7 +892,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                             self.sess,
                             sym::proc_macro_hygiene,
                             item.span,
-                            "non-inline modules in proc macro input are unstable",
+                            fluent_generated::expand_non_inline_modules_in_proc_macro_input_are_unstable,
                         )
                         .emit();
                     }