Fix: Unused recursive function expressions should be flagged (fixes #…

…10982)

lib/rules/no-unused-vars.js

@@ -223,6 +223,32 @@ module.exports = {
             return false;
         }
 
+        /**
+         * Gets a list of function definitions for a specified variable.
+         * @param {Variable} variable - eslint-scope variable object.
+         * @returns {ASTNode[]} Function nodes.
+         * @private
+         */
+        function getFunctionDefinitions(variable) {
+            const functionDefinitions = [];
+
+            variable.defs.forEach(def => {
+                const { type, node } = def;
+
+                // FunctionDeclarations
+                if (type === "FunctionName") {
+                    functionDefinitions.push(node);
+                }
+
+                // FunctionExpressions
+                if (type === "Variable" && node.init &&
+                    (node.init.type === "FunctionExpression" || node.init.type === "ArrowFunctionExpression")) {
+                    functionDefinitions.push(node.init);
+                }
+            });
+            return functionDefinitions;
+        }
+
         /**
          * Checks the position of given nodes.
          *
@@ -435,7 +461,7 @@ module.exports = {
          * @private
          */
         function isUsedVariable(variable) {
-            const functionNodes = variable.defs.filter(def => def.type === "FunctionName").map(def => def.node),
+            const functionNodes = getFunctionDefinitions(variable),
                 isFunctionDefinition = functionNodes.length > 0;
             let rhsNode = null;
 

tests/lib/rules/no-unused-vars.js

@@ -717,6 +717,29 @@ ruleTester.run("no-unused-vars", rule, {
             code: "(function(_a) {})();",
             options: [{ args: "all", caughtErrorsIgnorePattern: "^_" }],
             errors: [{ message: "'_a' is defined but never used." }]
+        },
+
+        // https://github.com/eslint/eslint/issues/10982
+        {
+            code: "var a = function () { a(); };",
+            errors: [{ message: "'a' is assigned a value but never used." }]
+        },
+        {
+            code: "var a = function(){ function foo() { a(); } };",
+            errors: [
+                { message: "'a' is assigned a value but never used." },
+                { message: "'foo' is defined but never used." }
+            ]
+        },
+        {
+            code: "const a = () => { a(); };",
+            parserOptions: { ecmaVersion: 2015 },
+            errors: [{ message: "'a' is assigned a value but never used." }]
+        },
+        {
+            code: "const a = () => () => { a(); };",
+            parserOptions: { ecmaVersion: 2015 },
+            errors: [{ message: "'a' is assigned a value but never used." }]
         }
     ]
 });