=== tests/cases/compiler/inOperatorWithFunction.ts ===
var fn = function (val: boolean) { return val; }
>fn : (val: boolean) => boolean
>function (val: boolean) { return val; } : (val: boolean) => boolean
>val : boolean
>val : boolean

fn("a" in { "a": true });
>fn("a" in { "a": true }) : boolean
>fn : (val: boolean) => boolean
>"a" in { "a": true } : boolean
>"a" : string
>{ "a": true } : { "a": boolean; }
>true : boolean