It's a dead-end. Sure, it can work in simple cases, but there will be always a case where such syntax recovery isn't possible. That's why relying only on syntax recovery isn't an option.
Because of that I use a different approach. I do parse on each document editing, but such parsing is guaranteed to produce valid results only up to the point with broken syntax, where editing usually takes place. Such parsing is enough to reconstruct location of the point where editing takes place (namespace/class/function) and to reconstruct local context (local variables declared prior to editing place). This allows to perform almost perfect autocompletion by suggesting global and local names available at the editing point. In order to provide proper suggestion of non-local names declared after the editing point, I do keep a structure for the most recent document state with valid syntax.
With features like "go to definition" I do the same. I store a hash-table with location to definition point mapping, but it's updated only from time to time and only if document syntax is valid. In order to be usable for cases with edits made after building such hash-table I just perform text-based position mapping using accumulated edit events.