Fix #576 (#587)

* Should fix #576

People were calling `"foo".toString() or ["foo", "bar"].toString()`, which returned the real JS string `"[object Object]"`, the stringified version of the replacements object.

* Prettier code means prettier green checkmarks

* Testing testing 123

* Forgot the parens around the object literal

* Semicolons!

* npm run format

packages/babel-plugin-minify-constant-folding/__tests__/constant-folding-test.js

@@ -237,4 +237,18 @@ describe("constant-folding-plugin", () => {
     );
     expect(transform(source)).toBe(expected);
   });
+
+  it("shouldn’t crash on toString() calls or accesses", () => {
+    const source = unpad(
+      `
+      "foo".toString();
+      ["foo", "bar"].toString();
+      ({}).toString();
+      "foo".toString;
+      ["foo", "bar"].toString;
+      ({}).toString;
+      `
+    );
+    expect(transform(source)).toBe(source);
+  });
 });

packages/babel-plugin-minify-constant-folding/src/index.js

@@ -22,7 +22,10 @@ function swap(path, member, handlers, ...args) {
   const key = getName(member);
   if (key === undefined) return;
   let handler = handlers[key];
-  if (typeof handler !== "function") {
+  if (
+    typeof handler !== "function" ||
+    !Object.hasOwnProperty.call(handlers, key)
+  ) {
     if (typeof handlers[FALLBACK_HANDLER] === "function") {
       handler = handlers[FALLBACK_HANDLER].bind(member.object, key);
     } else {