Is this correct: "I'd have to have had..."
Solution 1:
The grammar is correct, but the form is bad. Here is a better way to say it:
If I had gone to Canada, I'd have needed some kind of winter gear.
Solution 2:
Correct would be:
If I had gone to Canada, I would have had to have some kind of winter gear.
This is the Third Conditional because it refers to unreal situations in the past. Its form is:
if ... past perfect clause, would ... present perfect main clause.
For example:
If I had gone to Canada, I would have had some kind of winter gear.
or simpler:
If I'd gone to Canada, I would've had some kind of winter gear.
So you can see this is a phrase with 2 sentences (they are separated by comma when the if sentence comes first like in our case).
As a general rule, don't put would and if in the same sentence. If I would have... sounds pretty bad and it's nice to have it replaced by If I had... or by If I were..., just keep the would out of it :)
There also is a shorter way of putting this Third Conditional without using if at all:
Had I gone to Canada, I would've had some kind of winter gear.
Solution 3:
I think the sentence is fine. If it were spoken quickly, a native speaker would have no trouble understanding what is meant.
However, the use of the conditional in the if clause ("If I would have gone to Canada") is an informal style that many style guides would advise against. I personally would call it "clunky." The American Heritage Dictionary has a usage note about it, which I will quote here the sections relevant to this sentence: (see the AHD's site for the full note)
Although constructions using would have instead of had or did plus an infinitive instead of had and a past participle are common in informal speech (If you would've told me you were leaving, I could've gone with you), they are generally not considered correct in formal writing [...] the grammatical requirements are actually quite straightforward: 1. The if-clause must have a verb in the conditional subjunctive mood [...] When a writer wants to refer to a situation that hypothetically could have occurred in the past, a more remote past form must be used—the past tense of the preterite, also known as the past perfect or the pluperfect (If you had danced better...; If he had been rich...).
As such, the first part of the sentence is grammatical, but a pretty informal style. The second part, however, is a little tricky with all the variations of "have" in the coordinating consequent clause, but they all seem fine to me.
I'd have to have had some kind of winter gear.
To be clear, the I'd is I would, not I had, meaning, without the contraction, it's
I would have to have had some kind of winter gear.
Next, the would is as in sense 5 from AHD ("Used in the main clause of a conditional statement to express a possibility or likelihood") and have to here means must, in the auxiliary sense of "be required or logically consequent", as in "it would have to be freezing out if it were snowing":
I would have to [must] have had some kind of winter gear
The remaining have had is just the present perfect form of the plain verb have meaning possess.
I would have to have had [possessed] some kind of winter gear
In conclusion, I think the second part of the sentence is fine, but I would change the conditional in the if clause to past perfect subjunctive to not be so informal.
If I had gone to Canada, I'd have to have had some kind of winter gear.