Encode proc macro stability

src/librustc_metadata/decoder.rs

@@ -648,7 +648,7 @@ impl<'a, 'tcx> CrateMetadata {
 
     pub fn get_stability(&self, id: DefIndex) -> Option<attr::Stability> {
         match self.is_proc_macro(id) {
-            true => None,
+            true => self.root.proc_macro_stability.clone(),
             false => self.entry(id).stability.map(|stab| stab.decode(self)),
         }
     }

src/librustc_metadata/encoder.rs

@@ -490,7 +490,11 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             } else {
                 None
             },
-
+            proc_macro_stability: if is_proc_macro {
+                tcx.lookup_stability(DefId::local(CRATE_DEF_INDEX)).map(|stab| stab.clone())
+            } else {
+                None
+            },
             compiler_builtins: attr::contains_name(&attrs, "compiler_builtins"),
             needs_allocator: attr::contains_name(&attrs, "needs_allocator"),
             needs_panic_runtime: attr::contains_name(&attrs, "needs_panic_runtime"),

src/librustc_metadata/schema.rs

@@ -187,6 +187,7 @@ pub struct CrateRoot {
     pub has_default_lib_allocator: bool,
     pub plugin_registrar_fn: Option<DefIndex>,
     pub proc_macro_decls_static: Option<DefIndex>,
+    pub proc_macro_stability: Option<attr::Stability>,
 
     pub crate_deps: LazySeq<CrateDep>,
     pub dylib_dependency_formats: LazySeq<Option<LinkagePreference>>,