that !== null && typeof that === "object" still claims that that can be null

[derolf]

TypeScript Version: 4.0.2

Search Terms:

typeof, object, narrow, if, null

Code

function broken(that: unknown): object {
  if (that !== null && typeof that === "object") {
    return that;  // <--- ts(2322)
  }
  return {};
}

function works(that: unknown): object {
  if (typeof that === "object" && that !== null) {
    return that;
  }
  return {};
}

Expected behavior:

Compile.

Actual behavior:

Fails with error

Type 'object | null' is not assignable to type 'object'.
  Type 'null' is not assignable to type 'object'.ts(2322)

Playground Link:

https://www.typescriptlang.org/play?#code/GYVwdgxgLglg9mABAIwE5wNYFMwAooAWAhlAFyLgZhwDuYAlOXMgFZbSIDeAUIojMET5iURAEIAvBMRgQAGzmIAZEsRQAngAcscQYRKIp0gETM20Y-S68+iVFighUSfVADcNgL437j5108Pb25QSFgERBo4VAwAZ2ESckpqOkZEM3ZRHj4BIQ1tXTURQylEU1ZM42VVV3FS2QUrbNtfJxcRDz5vPlb-TkDuTyA

[MartinJohns]

Duplicate of #28131. Search terms used: null object

[RyanCavanaugh]

Thanks @MartinJohns!

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.