Anonymous function expressions aren't covered for 'infer from usage'

[DanielRosenwasser]

I'm not getting any codefixes on the parameters in the following example:

var f = function(x, y, z) {
    return 0 + x + y + z;
}

f(1, 2, 3)

At the very least, x, y, and z should infer from their bodies.

Optimally, we should climb up looking for PropertyAssignments, PropertyDeclarations, and BinaryExpressions (with = tokens), and VariableDeclarations. For those, we should find all references and figure out the type there.

Should also test for default exports as well.