rustc: Fix a suggestion for the `proc_macro` feature

This feature is stable, we shouldn't suggest it any more! Instead suggest the
real feature, `use_extern_macros`.

diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index f388b911feb6a5c6b02d435f31fd07b25ec9172d..177e4ed8cf376d31a08d3f8530d798dd278c729c 100644 (file)
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -4521,7 +4521,7 @@ fn check_proc_macro_attrs(&mut self, attrs: &[ast::Attribute]) {
                     attr::mark_known(attr);
 
                     let msg = "attribute procedural macros are experimental";
-                    let feature = "proc_macro";
+                    let feature = "use_extern_macros";
 
                     feature_err(&self.session.parse_sess, feature,
                                 attr.span, GateIssue::Language, msg)