Union strings for Discriminated Unions

[mushishi78]

TypeScript Version: 2.8.1, 2.6.1
Search Terms: Union strings, Discriminated Unions
Code

const a: { type: '1' } | { type: '2' } = null as { type: '1' | '2' }

Expected behavior: The types should be recognized as equivalent

Actual behavior:

Type '"1"' is not assignable to type '"2"'

Playground Link: https://www.typescriptlang.org/play/#src=const%20a%3A%20%7B%20type%3A%20'1'%20%7D%20%7C%20%7B%20type%3A%20'2'%20%7D%20%3D%20null%20as%20%7B%20type%3A%20'1'%20%7C%20'2'%20%7D%0D%0A

[RyanCavanaugh]

Duplicate of #12052

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.