[decorators] Support async and generator methods (#8742)

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/async-generator-method/input.js

@@ -0,0 +1,8 @@
+@decorator
+class Foo {
+  async f1() {}
+
+  *f2() {}
+
+  async *f3() {}
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/async-generator-method/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    ["proposal-decorators", { "decoratorsBeforeExport": false }],
+    "proposal-class-properties",
+    "syntax-async-generators",
+    ["external-helpers", { "helperVersion": "7.0.2" }]
+  ]
+}

packages/babel-plugin-proposal-decorators/test/fixtures/transformation/async-generator-method/output.js

@@ -0,0 +1,33 @@
+let Foo = babelHelpers.decorate([decorator], function (_initialize) {
+  "use strict";
+
+  class Foo {
+    constructor() {
+      _initialize(this);
+    }
+
+  }
+
+  return {
+    F: Foo,
+    d: [{
+      kind: "method",
+      key: "f1",
+
+      async value() {}
+
+    }, {
+      kind: "method",
+      key: "f2",
+
+      *value() {}
+
+    }, {
+      kind: "method",
+      key: "f3",
+
+      async *value() {}
+
+    }]
+  };
+});