Fix unnecessary self-move-assignments on calling deque erase(x,x)

[Arzaghi]

Fixes issue #1118
I think it's the simplest method to solve the issue. however, it adds a little bit overhead to the library with an additional IF.
Any better idea?

[miscco]

I believe the "conventional" solution would be to simply add

if (_First == _Last) {
    return _First;
}

at the beginning of the function.

[miscco]

Also note, that formatting seems to be off. You need to use clang-format 10 with the file setting

[Arzaghi]

I believe the "conventional" solution would be to simply add

if (_First == _Last) {
    return _First;
}

at the beginning of the function.

It adds an additional IF statement to the code as well. This IF statement will be effective in just a rare call.
It would be perfect if the algorithm handles the rare situation naturally.

[StephanTLavavej]

Thanks for fixing this!

I wonder whether we should have test coverage for this, but we can file a separate issue for that.

[StephanTLavavej]

Thanks for fixing this bug, and congratulations on your first microsoft/STL commit! 🎉 😸