roy compile error

gistfile1.txt

// Strong
console.log 40 + 2

// Won't compile:
// console.log "40" + 2

// Explicit
let f x: Number = x

console.log (f 100)

// Won't compile:
//console.log (f "100")

type Person = {firstName: String, lastName: String, friend: Person}
let getName (x: Person) = x.firstName ++ " " ++ x.lastName

console.log (getName {firstName: "Brian", lastName: "McKenna"})

// Won't compile:
console.log (getName {firstName: "", lastName: "", friend: {firstName: "", lastName: ""}})

// this is the worst form I've been able to see:
type Person = {first: String, last: String}
let p: Person = {first: "Fred", last: "dick"}
let getName (x: Person) = x.firstName ++ " " ++ x.lastName
console.log (getName p)

// Error: Type error on line 4: Person is not Person

EDIT: the code is actually wrong, but the error is unhelpful, the problem is that getName is calling non-existent firstName and lastName properties on Person