Diagnose cfged-out crate

src/tools/rust-analyzer/crates/hir-def/src/nameres/collector.rs

diff --git a/src/tools/rust-analyzer/crates/hir-def/src/nameres/collector.rs b/src/tools/rust-analyzer/crates/hir-def/src/nameres/collector.rs
index 9c101c1..703f070 100644
--- a/src/tools/rust-analyzer/crates/hir-def/src/nameres/collector.rs
+++ b/src/tools/rust-analyzer/crates/hir-def/src/nameres/collector.rs
@@ -22,7 +22,7 @@
 use la_arena::Idx;
 use rustc_hash::{FxHashMap, FxHashSet};
 use smallvec::SmallVec;
-use span::{Edition, FileAstId, SyntaxContext};
+use span::{Edition, FileAstId, ROOT_ERASED_FILE_AST_ID, SyntaxContext};
 use stdx::always;
 use syntax::ast;
 use triomphe::Arc;
@@ -369,7 +369,14 @@ fn seed_with_top_level(&mut self) {
 
         self.inject_prelude();
 
-        if matches!(item_tree.top_level_attrs(), AttrsOrCfg::CfgDisabled(_)) {
+        if let AttrsOrCfg::CfgDisabled(attrs) = item_tree.top_level_attrs() {
+            let (cfg_expr, _) = &**attrs;
+            self.def_map.diagnostics.push(DefDiagnostic::unconfigured_code(
+                self.def_map.root,
+                InFile::new(file_id.into(), ROOT_ERASED_FILE_AST_ID),
+                cfg_expr.clone(),
+                self.cfg_options.clone(),
+            ));
             return;
         }
 

src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/inactive_code.rs

diff --git a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/inactive_code.rs b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/inactive_code.rs
index dfa9639..9bfbeee 100644
--- a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/inactive_code.rs
+++ b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/inactive_code.rs
@@ -40,7 +40,10 @@ pub(crate) fn inactive_code(
 
 #[cfg(test)]
 mod tests {
-    use crate::{DiagnosticsConfig, tests::check_diagnostics_with_config};
+    use ide_db::RootDatabase;
+    use test_fixture::WithFixture;
+
+    use crate::{DiagnosticCode, DiagnosticsConfig, tests::check_diagnostics_with_config};
 
     #[track_caller]
     pub(crate) fn check(#[rust_analyzer::rust_fixture] ra_fixture: &str) {
@@ -212,4 +215,41 @@ fn cfg_true_false() {
 "#,
         );
     }
+
+    #[test]
+    fn inactive_crate() {
+        let db = RootDatabase::with_files(
+            r#"
+#![cfg(false)]
+
+fn foo() {}
+        "#,
+        );
+        let file_id = db.test_crate().root_file_id(&db);
+        let diagnostics = hir::attach_db(&db, || {
+            crate::full_diagnostics(
+                &db,
+                &DiagnosticsConfig::test_sample(),
+                &ide_db::assists::AssistResolveStrategy::All,
+                file_id.file_id(&db),
+            )
+        });
+        let [inactive_code] = &*diagnostics else {
+            panic!("expected one inactive_code diagnostic, found {diagnostics:#?}");
+        };
+        assert_eq!(
+            inactive_code.code,
+            DiagnosticCode::Ra("inactive-code", ide_db::Severity::WeakWarning)
+        );
+        assert_eq!(
+            inactive_code.message,
+            "code is inactive due to #[cfg] directives: false is disabled",
+        );
+        assert!(inactive_code.fixes.is_none());
+        let full_file_range = file_id.parse(&db).syntax_node().text_range();
+        assert_eq!(
+            inactive_code.range,
+            ide_db::FileRange { file_id: file_id.file_id(&db), range: full_file_range },
+        );
+    }
 }