Allow accessing global variable with `::` with a local with the same name in scope

[michaelstephendavies]

I expected this to work:

::x = 5;
fn addToX(x) {
        return ::x + x;
}
::console.log(addToX(2)); // 7

However it compiles to (with ES6 target):

"use strict";
(function () {
    x = 5;
    function addToX(x) {
        return x + x;
    }
    console.log(addToX(2)); // 4
}());

The compiler should maybe rename the local x so that the ::x accesses the global x:

x = 5;
function addToX(x_) {
    return x + x_;
}

The same should hold for local variables, and for use.

[joepvl]

We could just prefix the global variable with the global object in the compiler's output. The enclosing IIFE could be used to inject the global object into the scope (so there's no browser/node awkwardness). So the compiled code in this case would look like:

"use strict";
(function (global) {
    global.x = 5;
    function addToX(x) {
        return global.x + x;
    }
    global.console.log(addToX(2)); // 7
}(this));

This way, the forced explicitness of global scope use is actually reflected in the generated js code. It's also probably much easier to implement than having to modify non-global variable names that match global ones.

Also as far as I can tell, if a variable has been imported through a use statement, we don't need to apply this when that variable is referred to without ::, so we could get rid of the potentially unwanted global.console... above by writing use console; at the top of the Spider code.

[michaelstephendavies]

In the node.js case, things like require and module and exports are not available in this.

console.log(require);
console.log(module);
console.log(exports);
console.log(this.require);
console.log(this.module);
console.log(this.exports);

When run as a node script or required, this outputs three object literals, then three undefineds.