Ensure that the async/generator flags carry over when converting class methods - fixes T6755

packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/actual.js

@@ -0,0 +1,9 @@
+class Example {
+  async test1(){
+    await Promise.resolve(2);
+  }
+
+  *test2(){
+    yield 3;
+  }
+}

packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js

@@ -0,0 +1,30 @@
+"use strict";
+
+function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }
+
+var Example = (function () {
+  function Example() {
+    _classCallCheck(this, Example);
+  }
+
+  Example.prototype.test1 = async function test1() {
+    await Promise.resolve(2);
+  };
+
+  Example.prototype.test2 = regeneratorRuntime.mark(function test2() {
+    return regeneratorRuntime.wrap(function test2$(_context) {
+      while (1) {
+        switch (_context.prev = _context.next) {
+          case 0:
+            _context.next = 2;
+            return 3;
+
+          case 2:
+          case "end":
+            return _context.stop();
+        }
+      }
+    }, test2, this);
+  });
+  return Example;
+})();

packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "syntax-async-functions",
+    ["transform-es2015-classes", { "loose": true }]
+  ]
+}