Does this make (some) answering pre-February 2016 questions illegal after that date?

If someone asks:

I have this code, it doesn't work, how can I make it work?

I might know the answer and just copy his code, change a few characters to make it work and post that as an answer. Except, that I am not allowed to. His code is licensed CC-BY-SA but by putting it in my answer, I would license it as MIT. I am not allowed to do that.

Is this correct, or am I missing something?

Of course to make it legal I can answer it like

In line 5, you have to change the 3rd 'a' at position 16 to 'b' and in line x...

But if it is that cumbersome to answer, I might just not.

Does this potentially make answering pre-February 2016 questions illegal after that date?

If someone asks on January 31st:

I have this code, it doesn't work, how can I make it work?

then two days later, I might know the answer and just copy his code, change a few characters to make it work and post that as an answer. Except, that I am not allowed to. His code is licensed CC-BY-SA but by putting it in my answer, I would license it as MIT. I am not allowed to do that.

Is this correct, or am I missing something?

Of course to make it legal I can answer it like

In line 5, you have to change the 3rd 'a' at position 16 to 'b' and in line x...

But if it is that cumbersome to answer, I might just not.