Thread: Gone are the days when ...

How to decompose this phrase to subject/object correctly? What role does "gone" have exactly? (I understand meaning well. I have difficulties with subject-action-object roles of words.)

This is just "inversion" used for extra emphasis. As in:

Of that I have no doubt! Her I like! Never should I have done that! Never did I know what would happen etc, etc.

Your original sentence should just be viewed as:

The days are gone when...

Nothing more, just extra empasis on gone with that position, most likely to express sorrrow or regret for the good old days.

E.g If you watched the first "hunger games", there is a moment when Catniss gets interviewed before the games. IIRC in the original she says something like: "I will try to survive" and the interviewer response was:

"And try you will". This clearly expresses doubt that she will succeed but acknowledges that she will indeed try.

"gone" in this case is an adjective.

Specifically, it's the past participle of "go".

"I go."-- "I have gone." (the form used for the Perfect Tense, which involves "have/has", is the same as the Past Participle)
"The book is gone." (The adjectival use of the Past Participle)

Similar to:

сойти с ума ---- с-ума-сшедший
to go out of one's mind ---- gone out of one's mind

Past participles of English verbs usually are the same as the past tense, but a lot of words have a special form, most of the time ending in an -(e)n, as opposed to an -ed

present- past- past participle
see- saw- seen
bend- bent - bent
break- broke- broken
drive- drove- driven

I have drove 10 miles. I have driven 10 miles.

Past Participle Usages:
1. Perfect tense - I have seen.
2. Adjectival use - The man seen yesterday is still missing.
3. Predicative use - He is seen.