[Grammar] Would have done to have done v.s. would have done to do

[cubezero3]

Hi, everyone.

I was reading Agatha Christies's The Mysterious Affairs at Styles and encountered the following sentence.

Then, if there had been a large patch of candle grease on the floor you think you would have been sure to have seen it.

I'm under the impression that the 'would have done to have done something' structure is used to put things further aback, that is, we have three reference points in time: now (I'm telling you, which is implied), past (would have done), and past of the past (to have done something). This sentence seems to be the case.

The thing is, though I'm not entirely sure, I do think I've seen several cases where there is no putting things further aback when it comes to 'would have done to have done' v.s. 'would have done to do'. In other words, the former is used to mean more or less the latter. I know I should've waited till I can find an example to show such usage. But this structure is somewhat rare and I'm just not sure when I will encounter the usage in a long time.

I am really curious and would like to hear your opinions.

Rich

 

[tzfujimino]

https://books.google.co.jp/books?id...would have been sure to have seen it.&f=false

There should be a comma after "floor", and a question mark at the end of your sentence in the quote box.

I think it means the same as "..., you think you would have been sure that you had seen it?"

(Edit) It's the third conditional.
https://www.usingenglish.com/articles/english-conditionals-an-introduction.html#third

Also, it's be sure + the perfect infinitive (to have seen).