I see that “I would never” is sometimes translated with ‘asla ... -mezdim’

I would never go there. Asla oraya gitmezdim.
I would never betray you. Sana asla ihanet etmezdim.
I would never have guessed. Asla tahmin etmezdim.


I also see ´–medim’ as the translation for “I would never”

I would never ever do anything like that. Şimdiye kadar asla böyle bir şey yapmadım.
I would never betray you. Sana asla ihanet etmedim.
I would still use -mezdim here. And I would translate the Turkish sentences as:

I have never done something like that so far.

I have never betrayed you.

 

Or sometimes even with –mem. How come? Any example?


My question is: when do I use –mezdim instead of -medim or –mem?

And is –mezdim commonly used, I mean halk dillinde?

I would never ever do anything like that. Şimdiye kadar asla böyle bir şey yapmadım.
I would never betray you. Sana asla ihanet etmedim.
I would still use -mezdim here. And I would translate the Turkish sentences as:

I have never done something like that so far.

I have never betrayed you.

 

Thank you!

Yes but this is exactly where the difficulty is: I mean to say

"I would never do something like that" not "I have never done something like that".

The first sentence is kind of a promis. ´In a hypothetical situation, I wouldn´t do it´, or ´If I were you, I wouldn´t do it.´ 

= Ben olsam, öyle bir şey yapmazdım. OK also you may say

= Ben olsam, öyle bir şey yapmam.  But you need a context to mean it.

In general; I wouldn´t ... = ...-mazdım works always in my humble opinion.

Second sentence is a statement, a fact, non-hypothetical, about the past. 

Still I would translate it the same way again:

= Ben olsam, öyle bir şey yapmazdım.

You could also add (but not necessary)

= Ben olsa idim, öyle bir şey yapmazdım. We know the diffrence from the context if it is non-hypothetical, about the past or hypothetical in present time.

But I guess you are saying you would use -mezdim, it is common for you to use -mezdim, yes? yes