fix: register inserted class declaration (#10302)

* Decorators legacy: register inserted declaration

For compatibility with the Typescript plugin

Fixes #10264

* Register declaration but also keep replaceWithMultiple

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

@@ -237,7 +237,7 @@ export default {
 
     const replacement = decoratedClassToExpression(decl);
     if (replacement) {
-      path.replaceWithMultiple([
+      const [varDeclPath] = path.replaceWithMultiple([
         replacement,
         t.exportNamedDeclaration(null, [
           t.exportSpecifier(
@@ -246,6 +246,10 @@ export default {
           ),
         ]),
       ]);
+
+      if (!decl.node.id) {
+        path.scope.registerDeclaration(varDeclPath);
+      }
     }
   },
   ClassDeclaration(path) {

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/input.mjs

@@ -0,0 +1,4 @@
+function myDecorator(decoratee) {}
+
+@myDecorator
+export default class {}

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": [
+    "transform-typescript",
+    [ "proposal-decorators", { "legacy": true } ]
+  ]
+}

packages/babel-plugin-proposal-decorators/test/fixtures/legacy-regression/10264/output.mjs

@@ -0,0 +1,7 @@
+var _class2;
+
+function myDecorator(decoratee) {}
+
+let _class = myDecorator(_class2 = class {}) || _class2;
+
+export { _class as default };