Bladesinger vs. Eldritch Knight: what's in a Gish?

[Segev]

So, just to be clear, you think adding the feature of Bladesinger Extra Attack to Fighters Extra Attack, is not adding those features together? I whole heartily disagree and see no way that can logically work.

To be clear, here’s the wording of BS EA: “Starting at 6th level, you can attack twice, instead of once, whenever you take the Attack action on your turn. Moreover, you can cast one of your cantrips in place of one of those attacks.”

So are you also saying that “in place of one of [b]those attacks[\b]” is referencing the Fighters Extra Attacks ability for some reason?

I see no way to make that work, RAW.

There isn't "fighter's extra attacks" and "bladesinger's extra attacks." There's the number of attacks you're allowed. That's why they don't stack.