Add a coverage mark

crates/hir_def/src/body/tests/block.rs

@@ -348,6 +348,7 @@ fn foo() {
 #[test]
 fn is_visible_from_same_def_map() {
     // Regression test for https://github.com/rust-analyzer/rust-analyzer/issues/9481
+    cov_mark::check!(is_visible_from_same_block_def_map);
     check_at(
         r#"
 fn outer() {

crates/hir_def/src/visibility.rs

@@ -139,6 +139,7 @@ impl Visibility {
         let arc;
         let to_module_def_map =
             if to_module.krate == def_map.krate() && to_module.block == def_map.block_id() {
+                cov_mark::hit!(is_visible_from_same_block_def_map);
                 def_map
             } else {
                 arc = to_module.def_map(db);