function printStatusCode(code: string | number) {
console.log(`My status code is ${code.toUpperCase()}.`) // error: Property 'toUpperCase' does not exist on type 'string | number'. Property 'toUpperCase' does not exist on type 'number'
}
prog.ts(2,51): error TS2339: Property 'toUpperCase' does not exist on type 'string | number'. Property 'toUpperCase' does not exist on type 'number'.