[BUG/TypeScript] declare global conflict with block declaration

[shrinktofit]

Bug Report

• I would like to work on a fix!

Current behavior

Code

declare global { namespace globalThis { var i18n: any; } }

export class i18n {}

trigger an scope error:

    TypeError: Duplicate declaration "i18n"
      1 | declare global { namespace globalThis { var i18n: any; } }
      2 |
    > 3 | export class i18n {}
        |              ^^^^

      249 |     }
      250 | 
    > 251 |     return new Error(msg);
          |            ^
      252 |   }
      253 | 
      254 | }

      at File.buildCodeFrameError (packages/babel-core/lib/transformation/file/file.js:251:12)
      at Scope.checkBlockScopedCollisions (packages/babel-traverse/lib/scope/index.js:422:22)
      at Scope.registerBinding (packages/babel-traverse/lib/scope/index.js:582:16)
      at Scope.registerDeclaration (packages/babel-traverse/lib/scope/index.js:527:12)
      at Object.BlockScoped (packages/babel-traverse/lib/scope/index.js:250:12)
      at Object.newFn (packages/babel-traverse/lib/visitors.js:216:17)
      at NodePath._call (packages/babel-traverse/lib/path/context.js:55:20)
      at NodePath.call (packages/babel-traverse/lib/path/context.js:38:14)
      at NodePath.visit (packages/babel-traverse/lib/path/context.js:90:31)
      at TraversalContext.visitQueue (packages/babel-traverse/lib/context.js:116:16)

• REPL

Input Code

As described above.

Expected behavior

This piece of code is valid in TypeScript.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: babel.config.js

{
  "presets": ["@babel/preset-typescript"]
}

Environment

• Babel version(s): [e.g. v7.12.0]
• Node/npm version: [e.g. Node 12/npm 7]
• OS: [e.g. macOS 10.15.4, Windows 10]
• Monorepo: [e.g. yes/no/Lerna]
• How you are using Babel: [e.g. webpack, rollup, parcel, babel-register]

Possible Solution

Additional context

[babel-bot]

Hey @shrinktofit! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

[The-x-Theorist]

I'd like to work on this issue?