Add test for regression 4219

packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/actual.js

@@ -0,0 +1,5 @@
+function test(fn) {
+    return async (...args) => {
+    return fn(...args);
+    };
+}

packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/expected.js

@@ -0,0 +1,21 @@
+"use strict";
+
+function test(fn) {
+    var _this = this;
+
+    return function _callee() {
+        var _args = arguments;
+        return regeneratorRuntime.async(function _callee$(_context) {
+            while (1) {
+                switch (_context.prev = _context.next) {
+                    case 0:
+                        return _context.abrupt("return", fn.apply(undefined, _args));
+
+                    case 1:
+                    case "end":
+                        return _context.stop();
+                }
+            }
+        }, null, _this);
+    };
+}

packages/babel-plugin-transform-regenerator/test/fixtures/regression/4219/options.json

@@ -0,0 +1,7 @@
+{
+    "plugins": [
+        "transform-es2015-parameters", 
+        "transform-es2015-spread",
+        "transform-regenerator"
+    ]
+}