Correctly update bindings of decorated class declarations (#8566)

packages/babel-plugin-proposal-decorators/src/transformer-legacy.ts

@@ -324,7 +324,15 @@ const visitor: Visitor<PluginPass> = {
   ClassDeclaration(path) {
     const replacement = decoratedClassToExpression(path);
     if (replacement) {
-      path.replaceWith(replacement);
+      const [newPath] = path.replaceWith(replacement);
+
+      const decl = newPath.get("declarations.0");
+      const id = decl.node.id as t.Identifier;
+
+      // TODO: Maybe add this logic to @babel/traverse
+      const binding = path.scope.getOwnBinding(id.name);
+      binding.identifier = id;
+      binding.path = decl;
     }
   },
   ClassExpression(path, state) {

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/8559/input.mjs

@@ -0,0 +1,12 @@
+import {autobind} from 'core-decorators';
+
+export default function wrap() {
+	return function() {
+		class Foo {
+			@autobind
+			method() {}
+		}
+
+		return Foo;
+	};
+}

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/8559/options.json

@@ -0,0 +1,7 @@
+{
+  "targets": { "node": 8 },
+  "plugins": [
+    ["proposal-decorators", { "version": "legacy" }]
+  ],
+  "presets": ["env"]
+}

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/8559/output.js

@@ -0,0 +1,20 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = wrap;
+
+var _coreDecorators = require("core-decorators");
+
+function wrap() {
+  return function () {
+    var _class;
+
+    let Foo = (_class = class Foo {
+      method() {}
+
+    }, (babelHelpers.applyDecoratedDescriptor(_class.prototype, "method", [_coreDecorators.autobind], Object.getOwnPropertyDescriptor(_class.prototype, "method"), _class.prototype)), _class);
+    return Foo;
+  };
+}