Typescript: Inline value different than value from variable [duplicate]

Why does the save-call with myUser variable work but the call with inline value not work? Typescript playground

interface User {
    username: string;
}

function save(user: Partial<User>) {

}

const myUser = {
    username: 'John',
    foo: 'bar',
} as const;
// no error
this.save(myUser);

// error: Argument of type '{ username: string; foo: string; }' is not assignable to parameter of type 'Partial<User>'.
// Object literal may only specify known properties, and 'foo' does not exist in type 'Partial<User>'
this.save({
    username: 'John',
    foo: 'bar',
});