When declaring a declarative macro in an item it's only accessible inside it

src/librustc/hir/map/mod.rs

@@ -514,8 +514,7 @@ impl<'hir> Map<'hir> {
         &self.forest.krate.attrs
     }
 
-    pub fn get_module(&self, module: DefId) -> (&'hir Mod, Span, HirId)
-    {
+    pub fn get_module(&self, module: DefId) -> (&'hir Mod, Span, HirId) {
         let hir_id = self.as_local_hir_id(module).unwrap();
         self.read(hir_id);
         match self.find_entry(hir_id).unwrap().node {
@@ -525,7 +524,7 @@ impl<'hir> Map<'hir> {
                 ..
             }) => (m, span, hir_id),
             Node::Crate => (&self.forest.krate.module, self.forest.krate.span, hir_id),
-            _ => panic!("not a module")
+            node => panic!("not a module: {:?}", node),
         }
     }
 
@@ -679,6 +678,16 @@ impl<'hir> Map<'hir> {
         }
     }
 
+    /// Wether `hir_id` corresponds to a `mod` or a crate.
+    pub fn is_hir_id_module(&self, hir_id: HirId) -> bool {
+        match self.lookup(hir_id) {
+            Some(Entry { node: Node::Item(Item { node: ItemKind::Mod(_), .. }), .. }) |
+            Some(Entry { node: Node::Crate, .. }) => true,
+            _ => false,
+        }
+    }
+
+
     /// If there is some error when walking the parents (e.g., a node does not
     /// have a parent in the map or a node can't be found), then we return the
     /// last good `HirId` we found. Note that reaching the crate root (`id == 0`),

src/librustc_privacy/lib.rs

@@ -508,11 +508,7 @@ impl EmbargoVisitor<'tcx> {
         }
     }
 
-    fn update_macro_reachable_mod(
-        &mut self,
-        reachable_mod: hir::HirId,
-        defining_mod: DefId,
-    ) {
+    fn update_macro_reachable_mod(&mut self, reachable_mod: hir::HirId, defining_mod: DefId) {
         let module_def_id = self.tcx.hir().local_def_id(reachable_mod);
         let module = self.tcx.hir().get_module(module_def_id).0;
         for item_id in &module.item_ids {
@@ -524,19 +520,13 @@ impl EmbargoVisitor<'tcx> {
                 self.update_macro_reachable_def(hir_id, def_kind, vis, defining_mod);
             }
         }
-
         if let Some(exports) = self.tcx.module_exports(module_def_id) {
             for export in exports {
                 if export.vis.is_accessible_from(defining_mod, self.tcx) {
                     if let Res::Def(def_kind, def_id) = export.res {
                         let vis = def_id_visibility(self.tcx, def_id).0;
                         if let Some(hir_id) = self.tcx.hir().as_local_hir_id(def_id) {
-                            self.update_macro_reachable_def(
-                                hir_id,
-                                def_kind,
-                                vis,
-                                defining_mod,
-                            );
+                            self.update_macro_reachable_def(hir_id, def_kind, vis, defining_mod);
                         }
                     }
                 }
@@ -892,10 +882,14 @@ impl Visitor<'tcx> for EmbargoVisitor<'tcx> {
             self.tcx.hir().local_def_id(md.hir_id)
         ).unwrap();
         let mut module_id = self.tcx.hir().as_local_hir_id(macro_module_def_id).unwrap();
+        if !self.tcx.hir().is_hir_id_module(module_id) {
+            // `module_id` doesn't correspond to a `mod`, return early (#63164).
+            return;
+        }
         let level = if md.vis.node.is_pub() { self.get(module_id) } else { None };
         let new_level = self.update(md.hir_id, level);
         if new_level.is_none() {
-            return
+            return;
         }
 
         loop {

src/test/ui/macros/macro-in-fn.rs

@@ -0,0 +1,8 @@
+// run-pass
+#![feature(decl_macro)]
+
+pub fn moo() {
+    pub macro ABC() {{}}
+}
+
+fn main() {}