If I have a Java project in Eclipse, I can right-click on a method name and \"Open Call Hierarchy.\" Suppose I have two interfaces, A and B, that both specify a method x().
Eclipse should already do this. If you want to test it, go to your A interface, select the x() method and run 'Open Call Hierarchy' on it. Do the same for your x() method in interface B. You should get different code locations, unless you have a class which implements both, which you should never do. Doing so won't break any compilation or execution, you will just be doubly declaring the same method signature.
It may help to remove "Potential matches" from the search results. Try this:
Preferences -> General -> Search
And check "Ignore potential matches".
I have tried this with a frequently-overridden method, toString(). When I right-click on it and choose "Open Call Hierarchy," Eclipse happily searches through my entire workspace and returns all references to that method signature.
I often rely on Eclipse to go the opposite way: I select a method invocation and press F3 to Open Declaration. But I don't think Eclipse is able to go the direction you want, from the declaration to the calling reference.