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alexklyuev/guard-factory.ts

Created September 7, 2017 10:01
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guard-factory.ts
const gf = <B, C extends B>(fn: (x: B) => x is C): (x: B) => x is C => {
return ((x: B) => fn(x)) as (x: B) => x is C;
}
const isString = gf<any, string>((x): x is string => typeof x === 'string');
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