Implement template default types
Fixes phpstan/phpstan#4801
Feel free to rebase your PR without any Composer changes, I updated the parser on 1.9.x :)
@rvanvelzen Are you still interested in solving this? Having default values would be extremely handy!
@ruudk I won't have time to work on this in the foreseeable future, but I do intend to solve this.
That being said, anyone should feel free to take this over :)
@rvanvelzen I need to tell you that I really miss your contributions :) Not just this specific one, but in general - a PR from you was always something to look forward to :)