Yup, just you. It’s not a word. While “whose” sounds like it should be person related, it’s perfectly fine to use in association with a thing. “Who” on the other hand only refers to people. You’re probably riffing off of “its”, which is the possessive of “it”.
Well its colloquial either way, so acceptable in some informal speech, but “that’s” looks wrong without the apostrophe. I do realize that that violates the “apostrophe = contraction, one word = possessive” rule of who’s vs. whose etc.
I’ve never thought thats was a word. But I avoid whose with inanimate objects; I’d usually rephrase “whose headlights aren’t” as “with headlights not.” (I think I’ve often floundered for a whichs that corresponds to your thats but as my mouth starts to form “which” I quickly switch it to “with.” )
No, it’s more likely based on the use of who and that, depending on whether you’re referring to an animate or inanimate object. I guess I just feel there should be two equivalent words for the possessives.
A person who has red hair: correct.
A person whose hair is red: correct.
A house that has a green roof: correct.
A house thats roof is green: incorrect?
Okay, it may not be grammatically correct but it seems to me like it should be.
Shakes: Heh! Were you in Yosemite Valley twenty five years ago?
My sister and I were there, and, nearby us, were two kids who had just found a Swiss Army Knife someone had lost in the woods. They were exultant. “It gots a knife… It gots a corkscrew… It gots a scissors…”
Ever since then, “It gots” is our family in-joke for “fully-featured.” Like, someone just bought a new car. “Does it gots?” “Oh, yeah, it gots!”
It seems to me that “that” is possessive there, so if you have to use it, it should follow the regular rule for possessives and take an apostrophe s: “that’s.” “Whose” and “its” (as a possessive) don’t have apostrophes, but they are irregular. Everything else, AFAIK, must have one.
However, to use “whose” in that sentence would certainly be more standard, and, to my ear, more correct. Although the car that is being references is not a human being, in this particular case it is being spoken of a bit as it were human, and so capable of owning something.
If you must avoid the appearance of even slight anthropomorphism, you can use the semantically equivalent “if its”: “It’s dangerous to drive a car if its headlights aren’t working.”
And, no, that’s not rewording the sentence. “If its” means the same thing as “whose” in that context. The “if” is the conjunctive part, and the “its” is the possessive part. The only difference is exactly what you wanted to avoid–the implication that the car is a person.
Hence inventing a new word is unnecessary, not that it stopped the usage of “cromulent” for “legitimate.”