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=== tests/cases/compiler/extractInferenceImprovement.ts ===
// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
>obj : T
>key : Extract<K, string>
return obj[key];
>obj[key] : T[Extract<K, string>]
>obj : T
>key : Extract<K, string>
}
function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
>obj : T
>key : K
return obj[key];
>obj[key] : T[K]
>obj : T
>key : K
}
const s = Symbol();
>s : unique symbol
>Symbol() : unique symbol
>Symbol : SymbolConstructor
interface StrNum {
first: string;
>first : string
second: number;
>second : number
[s]: string;
>[s] : string
>s : unique symbol
}
const obj: StrNum = {} as any;
>obj : StrNum
>{} as any : any
>{} : {}
let prop: string;
>prop : string
// should work
prop = getProperty2(obj, 'first');
>prop = getProperty2(obj, 'first') : string
>prop : string
>getProperty2(obj, 'first') : string
>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
>obj : StrNum
>'first' : "first"
prop = getProperty3(obj, 'first');
>prop = getProperty3(obj, 'first') : string
>prop : string
>getProperty3(obj, 'first') : string
>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
>obj : StrNum
>'first' : "first"
// Should fail
prop = getProperty2(obj, s);
>prop = getProperty2(obj, s) : string
>prop : string
>getProperty2(obj, s) : string
>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
>obj : StrNum
>s : unique symbol
prop = getProperty3(obj, s);
>prop = getProperty3(obj, s) : string | number
>prop : string
>getProperty3(obj, s) : string | number
>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
>obj : StrNum
>s : unique symbol
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