How to "flip" an equality proposition in Coq?

Question

If I'm in Coq and I find myself in a situation with a goal like so:

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  x = y -> y = x

Is there a tactic that can can take care of this in one swoop? As it is, I'm writing

intros H. rewrite -> H. reflexivity.

But it's a bit clunky.

Answer 1

To "flip" an equality H: x = y you can use symmetry in H. If you want to flip the goal, simply use symmetry.