declare function getStringOrNumber(): string | number;

// The type guard for x remains in effect in the arrow function because x is a const local.
// Had x been declared using let or var, the type guard would not be in effect.
function f1() {
    const x = getStringOrNumber();
    if (typeof x === "string") {
        const f = () => x.length;  // Ok
    }
}

// Type guard for x remains in effect in the IIFE.
function f2() {
    let x = getStringOrNumber();
    if (typeof x === "string") {
        let n = function() {
            return x.length;  // Ok
        }();
    }
}

// Type guard for x remains in effect and assignment to y is known to
// have executed before IIFE is invoked.
function f3() {
    let x = getStringOrNumber();
    let y: number;
    if (typeof x === "string") {
        let n = (z => x.length + y + z)(y = 1);
    }
}