Enums does not support literal typing with computed values · Issue #27976 · microsoft/TypeScript (original) (raw)

TypeScript Version: 3.2.0-dev.201xxxxx

Search Terms:

• enum flag
• enum computed literal typing

Code

enum AnimalFlags { None = 0, HasClaws = 1 << 0, CanFly = 1 << 1, EatsFish = 1 << 2, Endangered = 1 << 3,

EndangeredFlyingClawedFishEating = HasClaws | CanFly | EatsFish | Endangered,

}

enum RegularEnum { None, HasPowers, }

const a = AnimalFlags.EatsFish; const b: AnimalFlags.EndangeredFlyingClawedFishEating = AnimalFlags.EndangeredFlyingClawedFishEating; const c = RegularEnum.HasPowers;

Expected behavior:

a Should have type of AnimalFlags.EatsFish
b Should not throw. Should allow the assignment of AnimalFlags.EndangeredFlyingClawedFishEating as type.

I would expect a computed Enum to behave as a regular enum, in this case, c has type RegularEnum.HasPowers

Actual behavior:

a is typed as AnimalFlags.
const b: AnimalFlags.EndangeredFlyingClawedFishEating is throwing Enum type 'AnimalFlags' has members with initializers that are not literals.
b should be allowed to be typed as AnimalFlags.EndangeredFlyingClawedFishEating.

Playground Link:

Link

Related Issues:

I think is the same that one reported last year #18393. It was closed as a Design Limitation, but since there has been some big changes in Typescript maybe this would be worth to be reviewed again.