Talk to him is what I did.
(this sentence is from forum.wordreference.com)
"Talk" is a verb here that is not in the imperative mood. I suppose, it's in the infinitive form. But then how can it stand alone, without "to"?
What will be if we add "to" to "talk"?
To talk to him is what I did.
If we can do so, then what will difference be between the initial sentence and the new one with "to"?
Maybe, there are some omitted words, after inserting which the sentence will immediately become understandable? I mean, maybe, there is an ellipsis?
To make it clearer:
Upd.1: if we type "bare infinitive" in google, we can't find any sites that could explain the absence from "to" before "talk".
Upd.2: Why can we replace "to talk" with only "talk" in "To talk to him is what I did."
Upd.3: I have my own logic but I don't know whether it's right or not:
1) I think that without an ellipsis "Talk to him is what I did." is to look like "I did talk to him is what I did do."
2) Also I know that we can't use "to" before "read" in "What we must do is read the manual." because in the left part we don't have "to" before "do".
By this logic, we can't use "to" before "talk" in "Talk to him is what I did." because in "what I did do" we don't have "to" before "do".
Am I right or not?