Hey, I think I found what's either a bug or a confusing way that globals and ambient types are handled (potentially similarly to theno-undef issuementioned in the FAQs).

I'm currently migrating a large codebase to use TypeScript. We have a globalhas() function that we use to determine what environment we're in. It's handled by our build system, and is set as a read-only global in our existing ESLint config.

When I try and declare an ambient type for this global, I've noticed that@typescript-eslint/no-shadow thinks that I'm shadowing it. Removingglobals: { has: false } from the config fixes this problem. Is this expected behavior?

Thanks in advance, and sorry if I'm overlooking something.

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I haveread the FAQ and my problem is not listed.

Repro

I set up a fresh project by running the following in an empty directory:

yarn init -yyarn add -D eslint typescript @typescript-eslint/parser @typescript-eslint/eslint-plugin

I then added these two files

// .eslintrc.jsmodule.exports={root:true,parser:'@typescript-eslint/parser',plugins:['@typescript-eslint',],extends:['eslint:recommended','plugin:@typescript-eslint/recommended',],globals:{has:false,},rules:{"no-shadow":"off","@typescript-eslint/no-shadow":["error",{builtinGlobals:true}],}};

// index.d.tsdeclareconsthas:(environment:"dev"|"prod"|"test")=>boolean;

Expected Result

I'd expectyarn eslint index.d.ts to not error.

Actual Result

It logged the following error:

 1:15  error  'has' is already declared in the upper scope  @typescript-eslint/no-shadow

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