=== tests/cases/compiler/inOperatorWithFunction.ts ===
var fn = function (val: boolean) { return val; }
>fn : Symbol(fn, Decl(inOperatorWithFunction.ts, 0, 3))
>val : Symbol(val, Decl(inOperatorWithFunction.ts, 0, 19))
>val : Symbol(val, Decl(inOperatorWithFunction.ts, 0, 19))

fn("a" in { "a": true });
>fn : Symbol(fn, Decl(inOperatorWithFunction.ts, 0, 3))