For any set $X$ and cardinal $\kappa$ let $[X]^\kappa$ be the collection of all subsets of $X$ of cardinality $\kappa$.
I was looking for $T_2$-spaces $(X,\tau)$ with the property that
$(P)$ there is an injective function $f:[X]^\omega\to \tau$ such that for all $s\in [X]^\omega$ we have $s\subseteq f(s)$.
Question. If $(X,\tau)$ is infinite, Hausdorff, and non-separable, is there a function with the properties described in $(P)$?
Note. I had the following remark in the original version of this post, but KP Hart made me aware that it is false - thanks for spotting my mistake!
[False] Obviously, if $(X,\tau)$ is separable and contains at least two different countable dense subsets $s$, $s'$, then the only member of $\tau$ that contains $s$ or $s'$ is $X$ itself, so there cannot be an injective function $f$ as described in $(P)$. [/False]