fix no-unused-vars issue with spread

Use a private _spread property on Property node instead of SpreadProperty

Fixes https://github.com/babel/babel-eslint/issues/142#issuecomment-118707124

eslint/babel-eslint-parser/acorn-to-esprima.js

@@ -172,7 +172,9 @@ var astTransformVisitor = {
   noScope: true,
   exit: function (node) { /* parent */
     if (this.isSpreadProperty()) {
-      node.type = "SpreadProperty";
+      // private var to track if it's a spread property
+      node._spread = true;
+      node.type = "Property";
       node.kind = "init";
       node.computed = true;
       node.key = node.value = node.argument;

eslint/babel-eslint-parser/index.js

@@ -266,7 +266,7 @@ function monkeypatch() {
         if (id.type === "ObjectPattern") {
           // check if object destructuring has a spread
           var hasSpread = id.properties.filter(function(p) {
-            return p.type === "SpreadProperty"
+            return p._spread === true;
           });
           // visit properties if so
           if (hasSpread.length > 0) {

eslint/babel-eslint-parser/test/non-regression.js

@@ -1179,4 +1179,18 @@ describe("verify", function () {
       [ "1:7 Bacona is defined but never used no-unused-vars" ]
     );
   });
+
+  it("don't warn no-unused-vars with spread #142", function () {
+    verifyAndAssertMessages([
+        "export default function test(data) {",
+          "return {",
+            "foo: 'bar',",
+            "...data",
+          "};",
+        "}",
+      ].join("\n"),
+      { "no-undef": 1, "no-unused-vars": 1 },
+      []
+    );
+  });
 });