Arrow functions should not have a 'prototype' property

[DanielRosenwasser]

function f() {
    var a = () => 5;
    return a.prototype;
}

We should give an error here.

[RyanCavanaugh]

I think we have no way to do this? The apparent type of a callable type includes the members from the global type Function and we can't really remove prototype from that declaration.

[mhegazy]

The only way would be to have lambda functions have a different apparent type from regular functions.