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=== tests/cases/compiler/typePredicateTopLevelTypeParameter.ts ===
// Repro from #51980
function getPermissions(user: string) {
>getPermissions : (user: string) => "admin" | undefined
>user : string
if (user === 'Jack') return 'admin';
>user === 'Jack' : boolean
>user : string
>'Jack' : "Jack"
>'admin' : "admin"
return undefined;
>undefined : undefined
}
const admins = ['Mike', 'Joe'].map(e => getPermissions(e));
>admins : ("admin" | undefined)[]
>['Mike', 'Joe'].map(e => getPermissions(e)) : ("admin" | undefined)[]
>['Mike', 'Joe'].map : <U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => U[]
>['Mike', 'Joe'] : string[]
>'Mike' : "Mike"
>'Joe' : "Joe"
>map : <U>(callbackfn: (value: string, index: number, array: string[]) => U, thisArg?: any) => U[]
>e => getPermissions(e) : (e: string) => "admin" | undefined
>e : string
>getPermissions(e) : "admin" | undefined
>getPermissions : (user: string) => "admin" | undefined
>e : string
function isDefined<T>(a: T | undefined): a is T {
>isDefined : <T>(a: T | undefined) => a is T
>a : T | undefined
return a !== undefined;
>a !== undefined : boolean
>a : T | undefined
>undefined : undefined
}
const foundAdmins = admins.filter(isDefined); // "admin"[]
>foundAdmins : "admin"[]
>admins.filter(isDefined) : "admin"[]
>admins.filter : { <S extends "admin" | undefined>(predicate: (value: "admin" | undefined, index: number, array: ("admin" | undefined)[]) => value is S, thisArg?: any): S[]; (predicate: (value: "admin" | undefined, index: number, array: ("admin" | undefined)[]) => unknown, thisArg?: any): ("admin" | undefined)[]; }
>admins : ("admin" | undefined)[]
>filter : { <S extends "admin" | undefined>(predicate: (value: "admin" | undefined, index: number, array: ("admin" | undefined)[]) => value is S, thisArg?: any): S[]; (predicate: (value: "admin" | undefined, index: number, array: ("admin" | undefined)[]) => unknown, thisArg?: any): ("admin" | undefined)[]; }
>isDefined : <T>(a: T | undefined) => a is T
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