Thread: Colloquial (?) structure I don't quite get

Yes, colloquial and a little bit archaic maybe.

Уснуть так и не уснул.

Let us separate two constructions: "так и не", which is complicated by itself, and "verb infinitive + same verb in any other form".

The second is just an intensive one (the way to emphasize) and used mainly in contrapositions.

Уснуть - уснул, но не отдохнул.
As for sleeping, I did it, but was unable to relax.

I think it can mean "never."
I wanted to fall asleep but never did.
" " ...to catch (something?) " ".
..return ...