I see that people have been looking for sharing their phone's Wi-Fi (not 4G) with their laptop or computer, and I'm quite surprised to see that the community in general believing that this is not possible!! I've been using my HTC Desire 510 as a Wi-Fi sharing device for over 1.5 years now. All that's required is a "HTC Sync Manager" software installed on the laptop and turning on the "USB Tethering" ON on the mobile. Meanwhile, I must confess that I have not found a workaround using either my ASUS phone or using other devices such as Samsung. But the HTC Sync Manager and HTC Desire works in perfect harmony!!
Connecting a laptop to the WiFi is a lot easier than going through a phone connected to that same WiFi. Plus the solution is only good for the particular phone brand as you say, it's not really sharing WiFi with a phone, it's more sharing WiFi with the HTC Desire phone, that is a pretty important distinction to make.