Generic parameter is considered object

[svatal]

TypeScript Version: 3.1.0-dev.201xxxxx

Search Terms: generics, typeof, object, never

Code

function f<TData>(data: TData): boolean {
  if (typeof data === "object") return true;
  return data;
}

let x: boolean = f(1);

Expected behavior:
Code should not compile - function actually returns boolean | TData, but states only boolean

Actual behavior:
Code compiles without errors. After the if statement, data is considered never

Playground Link: http://www.typescriptlang.org/play/#src=function%20f%3CTData%3E(data%3A%20TData)%3A%20boolean%20%7B%0D%0A%20%20%20%20if%20(typeof%20data%20%3D%3D%3D%20%27object%27)%0D%0A%20%20%20%20%20%20%20%20return%20true%3B%0D%0A%20%20%20%20return%20data%3B%0D%0A%7D%0D%0A%0D%0Alet%20x%3A%20boolean%20%3D%20f(1)%3B

Related Issues:

[ahejlsberg]

This is fixed by #27157.