Simple String union can be compared against the wrong string values

[AlexGalays]

TypeScript Version: 2.0.0

Code

type Role = 'admin' | 'user'

const role: Role = 'admin'

if (role === '&!?# completelyrandom') {
   console.log(role)
}

Expected behavior:
I would expect simple if/ternary statements to be the idiomatic way to "type guard" string enums, but it doesn't do anything at compile time.

Actual behavior:
No error

[ahejlsberg]

This has the expected behavior in the current nightly build.

[AlexGalays]

Ok thanks, will update my beta version.

[DanielRosenwasser]

Duplicate of #6149.