Allow "T extends enum" generic constraint
See original GitHub issueTypeScript has a discrete enum
type that allows various compile-time checks and constraints to be enforced when using such types. It would be extremely useful to allow generic constraints to be limited to enum types - currently the only way to do this is via T extends string | number
which neither conveys the intent of the programmer, nor imposes the requisite type enforcement.
export enum StandardSortOrder {
Default,
Most,
Least
}
export enum AlternativeSortOrder {
Default,
High,
Medium,
Low
}
export interface IThingThatUsesASortOrder<T extends enum> { // doesn't compile
sortOrder: T;
}
Issue Analytics
- State:
- Created 4 years ago
- Reactions:204
- Comments:27 (4 by maintainers)
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I have a use case for this as well. I have a Select component that I want to make generic by taking any enum. I expect the caller to pass in a map of enumValue -> string labels.
If this feature existed, I could make a component like
Which would guarantee type-safety. (The compiler would prevent the developer ever forgetting to map a certain enum value to a user-friendly string representation)
Because I want to allow
IThingThatUsesASortOrder
to be used with any enum type.