Why does passing a number when a string is expected not fail compilation

Question

I have the following code where I am passing a number to a function which takes a string.
const getGreeting: Function = (name: String): String => {
    return `hello, ${name}`;
};

const x: number = 2
console.log(getGreeting(x))

I can understand why the outputted javascript works but why does this not result in a compilation error?

Orelsanpls · Answer

It doesnt result to an error because casting your function to Function makes typescript to loose the details of your method.
To make it work, type properly getGreeting like :
playground
const getGreeting: (name: string) => string = (name: string): string => {
    return `hello, ${name}`;
};

const x: number = 2

console.log(getGreeting(x));

Or let typescript to infer the type itself :
playground
const getGreeting = (name: string): string => {
    return `hello, ${name}`;
};

const x: number = 2

console.log(getGreeting(x));

Why does passing a number when a string is expected not fail compilation

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