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shqld/nominal_number_types.ts

Created April 7, 2022 11:44
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Nominal Number types in TypeScript
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nominal_number_types.ts
class Flavoring<FlavorT> {
private _flavor?: FlavorT;
}
type Flavor<Base, Flavor> = Base & Flavoring<Flavor>;
type i32 = Flavor<number, 'i32'>
type i64 = Flavor<number, 'i64'>;
const a: i32 = 1
const b: i64 = 2
let c = a
c = b // ERROR: Type 'i64' is not assignable to type 'i32'.
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shqld commented Apr 7, 2022

https://www.typescriptlang.org/play?#code/MYGwhgzhAEBi4DcD2AnAlgOwOYB55mRQBUA+aAbwChoboAHdBMAFwFNoB9AM0VQH4AXHF7EA3JQC+lSswCeddvkI4AQpFYAaYQVRkAvNDUR2AMm2FMuJbvEz57NAGYATNAPWUODAFcAtgCNWFC0AcidnEJI7BWg0ADYAFjdzVC8-QODoMMTI22AkDAhmaDAhcOSARkp8wuL-MsTk52kQVmLgZLBpDoN-SiA

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