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=== tests/cases/compiler/typeGuardNarrowsIndexedAccessOfKnownProperty2.ts ===
const foo: { key?: number } = {};
>foo : { key?: number | undefined; }
>key : number | undefined
>{} : {}
const key = 'key' as const;
>key : "key"
>'key' as const : "key"
>'key' : "key"
if (foo[key]) {
>foo[key] : number | undefined
>foo : { key?: number | undefined; }
>key : "key"
foo[key]; // number
>foo[key] : number
>foo : { key?: number | undefined; }
>key : "key"
foo.key; // number
>foo.key : number
>foo : { key?: number | undefined; }
>key : number
}
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