returnValue of calls is out of order when spying on recursive functions

Describe the bug

The return value, as given by spy.getCall(n).returnValue, is in the wrong order when spying on a recursive function. The return values are in the order that calls returned, instead of the order of the calls themselves. For example, the returnValue of the first call is the value returned by the last call, instead of the value returned by the first call.

Note that this bug occurs with both sinon.spy and sinon.fake.

To Reproduce

recurse.js

function foo(num) {
    if (num < 2) {
        foo(num + 1);
    }

    return num;
}

recurse.test.js

const rewire = require('rewire');
const expect = require('chai').expect;
const sinon = require('sinon');

const recurse = rewire('../recurse');


describe('foo', function () {
    it('should recursively add 1 but return original number', function () {
        recurse.__with__({
            foo: sinon.fake(recurse.__get__('foo'))
        })(function () {
            recurse.__get__('foo')(0);

            expect(recurse.__get__('foo').getCall(0).returnValue).to.equal(0);
            expect(recurse.__get__('foo').getCall(1).returnValue).to.equal(1);
            expect(recurse.__get__('foo').getCall(2).returnValue).to.equal(2);
        });
    });
});

Expected behavior

spy.getCall(n).returnValue should be the return value of the nth call to spy.

Context:

• Library version: 6.0.1
• Environment: Windows
• Other libraries you are using: mocha, chai, rewire

Start by running the recursive reproduction in recurse.test.js with the sinon.fake wrapper around recurse.js, then trace how calls are recorded for sinon.spy and sinon.fake. Confirm the failure with getCall(n).returnValue and ensure the return value for each call matches that call's invocation order, including nested recursive calls.