What is the name of this grammatical phenomenon?
I have observed that many native English speakers (esp. American English, in my experience) tend, within the same sentence, to start a new clause whose subject is an element of the previous clause. Here is an example: > That is what fascinated me about programming—is that it changes the way you think about the world. In this sentence, "what fascinated me about programming" is used as an object in the first clause, but then gets reused as the subject of the second clause. Other examples: - > This is something we talk about a lot—is the size of the community is substantially smaller than the React community [...] ([source](https://www.youtube.com/watch?v=LCNs92YQjhw#t=3m05s)) - > This is what I think went wrong is what Trump did very effectively is tap the angst and the anger and the hurt and the pain that millions of working-class people are feeling. ([source](https://www.youtube.com/watch?v=zlmuKtyhDKg&t=59s)) I have only noticed this phenomenon in spoken English, as opposed to written English. What are its name and origins? Note: I'm aware of the *double copula* (a.k.a. "double is"); this is related, but different.