From a943f576d1f7181abc593f97b174fdcf8a6c421d Mon Sep 17 00:00:00 2001
From: Sneh Khatri <khatris2014@gmail.com>
Date: Sun, 5 Dec 2021 22:54:56 +0530
Subject: [PATCH] Fix duplicate declaration error on ambient class declarations
 (#14016)

---
 packages/babel-traverse/src/scope/index.ts |  1 +
 packages/babel-traverse/test/scope.js      | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/packages/babel-traverse/src/scope/index.ts b/packages/babel-traverse/src/scope/index.ts
index 93aa94101602..e2eb17d8f724 100644
--- a/packages/babel-traverse/src/scope/index.ts
+++ b/packages/babel-traverse/src/scope/index.ts
@@ -706,6 +706,7 @@ export default class Scope {
         this.registerBinding(path.node.kind, declar);
       }
     } else if (path.isClassDeclaration()) {
+      if (path.node.declare) return;
       this.registerBinding("let", path);
     } else if (path.isImportDeclaration()) {
       const specifiers = path.get("specifiers");
diff --git a/packages/babel-traverse/test/scope.js b/packages/babel-traverse/test/scope.js
index 9ed72bef2690..1ecc76346792 100644
--- a/packages/babel-traverse/test/scope.js
+++ b/packages/babel-traverse/test/scope.js
@@ -655,6 +655,18 @@ describe("scope", () => {
       });
     });
 
+    describe("duplicate declaration", () => {
+      it("should not throw error on duplicate class and function declaration", () => {
+        const ast = [
+          t.classDeclaration(t.identifier("A"), t.super(), t.classBody([]), []),
+          t.functionDeclaration(t.identifier("A"), [], t.blockStatement([])),
+        ];
+
+        ast[0].declare = true;
+        expect(() => getPath(ast)).not.toThrowError();
+      });
+    });
+
     describe("global", () => {
       // node1, node2, success
       // every line will run 2 tests `node1;node2;` and `node2;node1;`