TypeScript 3.4+
TypeScript version 3.4 has introduced so-called **const contexts**, which is a way to declare a tuple type as immutable and get the narrow literal type directly (without the need to call a function like shown above).
With this new syntax, we get this nice concise solution:
const furniture = ['chair', 'table', 'lamp'] as const;
type Furniture = typeof furniture[number];
More about the new const contexts is found in this PR as well as in the release notes.
TypeScript 3.0+
With the use of generic rest parameters, there is a way to correctly infer string[] as a literal tuple type and then get the union type of the literals.
It goes like this:
const tuple = <T extends string[]>(...args: T) => args;
const furniture = tuple('chair', 'table', 'lamp');
type Furniture = typeof furniture[number];