title: Cannot find name 'Omit' in Typescript
body: <h1>Background</h1>
  
  <p>I'm making my custom <code>index.d.ts</code> file on <code>src/@types/index.d.ts</code>.
  I needed to merge my type like below.</p>
  
  <pre><code>// src/@types/index.d.ts
  declare namespace Admin {
    interface InitialStateFromDB {
      teamSettings: {
        teamPasswords: TeamPassword[],
        teamCount: number
      },
      adminPasswords: string,
      postInfos: PostInfo[] | undefined
    }
    interface InitialState extends Omit&lt;InitialStateFromDB, 'adminPasswords'&gt; {
      adminPasswords: AdminPassword
    }
  }
  </code></pre>
  
  <h1>Problem</h1>
  
  <p>I got error : <code>Cannot find name 'Omit'.ts(2304)</code> by VSCode Intellisense. But compile worked well.</p>
  
  <p>So, I made Omit type <code>type Omit&lt;T, K extends keyof T&gt; = Pick&lt;T, Exclude&lt;keyof T, K&gt;&gt;</code> (copied in <a href="https://stackoverflow.com/a/53936938/9279003">here</a>)</p>
  
  <p>And after compile, I got another error : <code>'Omit' was also declared here.</code></p>
  
  <p>What should I do in this case? Just ignore IntelliSense's error ?</p>