Demonstration of the "Duplicate declaration" error in Babel.

.babelrc

{
  "presets": [
    [
      "@babel/preset-env",
      {
        "targets": {
          "node": 8
        }
      }
    ]
  ],
  "plugins": [
    ["@babel/plugin-proposal-decorators", {"legacy": true}]
  ]	
}

README.md

babel-duplicate-definition-error

Demonstration of the "Duplicate declaration" error in Babel.

git clone https://gist.github.com/81ab0e3f823ce287d1bd8b2a65b4ad52.git
cd 81ab0e3f823ce287d1bd8b2a65b4ad52/
npm install
npm start

TypeError: .../babel-duplicate-definition-error/index.js: Duplicate declaration "Foo"
  3 | export default function wrap() {
  4 |   return function() {
> 5 |           class Foo {
    |                 ^
  6 |                   @autobind
  7 |                   method() {}
  8 |           }
    at File.buildCodeFrameError (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/core/lib/transformation/file/file.js:259:12)
    at Scope.checkBlockScopedCollisions (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/scope/index.js:347:22)
    at Scope.registerBinding (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/scope/index.js:504:16)
    at Scope.registerDeclaration (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/scope/index.js:444:14)
    at Object.BlockScoped (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/scope/index.js:189:28)
    at Object.newFn (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/visitors.js:230:17)
    at NodePath._call (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/path/context.js:53:20)
    at NodePath.call (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/path/context.js:36:14)
    at NodePath.visit (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/path/context.js:88:12)
    at TraversalContext.visitQueue (/private/tmp/babel-duplicate-definition-error/node_modules/@babel/traverse/lib/context.js:118:16)

index.js

import {autobind} from 'core-decorators';

export default function wrap() {
	return function() {
		class Foo {
			@autobind
			method() {}
		}

		return Foo;
	};
}

package.json

{
  "name": "babel-duplicate-definition-error",
  "version": "1.0.0",
  "scripts": {
    "start": "babel index.js"
  },
  "author": "Daniel Friesen <[email protected]>",
  "license": "MIT",
  "devDependencies": {
    "@babel/cli": "^7.0.0",
    "@babel/core": "^7.0.0",
    "@babel/plugin-proposal-decorators": "^7.0.0",
    "@babel/preset-env": "^7.0.0"
  },
  "dependencies": {
    "core-decorators": "^0.20.0"
  },
  "private": true
}