fix(linter/no-unused-vars): panic when variable is redeclared as function in same scope

crates/oxc_linter/src/rules/eslint/no_unused_vars/tests/oxc.rs

@@ -203,6 +203,24 @@ fn test_vars_self_use() {
         .test_and_snapshot();
 }
 
+#[test]
+fn test_vars_self_use_js() {
+    let pass = vec![
+        // https://github.com/oxc-project/oxc/issues/11215
+        "export function promisify() { var fn; function fn() {} return fn; }",
+    ];
+
+    let fail = vec![
+        // https://github.com/oxc-project/oxc/issues/11215
+        "export function promisify() { var fn; function fn() { fn() } }",
+    ];
+
+    Tester::new(NoUnusedVars::NAME, NoUnusedVars::PLUGIN, pass, fail)
+        .change_rule_path_extension("js")
+        .intentionally_allow_no_fix_tests()
+        .test();
+}
+
 #[test]
 fn test_vars_discarded_reads() {
     let pass = vec![

crates/oxc_linter/src/rules/eslint/no_unused_vars/usage.rs

@@ -745,7 +745,18 @@ impl<'a> Symbol<'_, 'a> {
     fn is_self_call_simple(&self, reference: &Reference) -> bool {
         let decl_scope_id = self.scope_id();
         let call_scope_id = self.get_ref_scope(reference);
-        let Some(container_id) = self.declaration().kind().get_container_scope_id() else {
+        let redeclarations = self.scoping().symbol_redeclarations(self.id());
+        let container_id = if redeclarations.is_empty() {
+            self.declaration().kind().get_container_scope_id()
+        } else {
+            // Syntax like `var a = 0; function a() { a() }` is legal. We need to
+            // check the redeclarations to find the one that is a function and use
+            // its scope id as the container id.
+            let declaration = redeclarations.iter().find(|decl| decl.flags.is_function()).unwrap();
+            self.nodes().get_node(declaration.declaration).kind().get_container_scope_id()
+        };
+
+        let Some(container_id) = container_id else {
             debug_assert!(
                 false,
                 "Found a function call or or new expr reference on a node flagged as a function or class, but the symbol's declaration node has no scope id. It should always be a container."
@@ -860,8 +871,8 @@ impl<'a> Symbol<'_, 'a> {
     ///
     /// A variable scope is the closest ancestor scope (including `scope_id`
     /// itself) whose kind can *outlive* the current execution slice:
-    ///   * function‑like scopes  
-    ///   * class static blocks  
+    ///   * function‑like scopes
+    ///   * class static blocks
     ///   * TypeScript namespace/module blocks
     fn get_parent_variable_scope(&self, scope_id: ScopeId) -> ScopeId {
         self.scoping()