New answers tagged syntax
It would break existing code if you could override == comparison, or even = assignment. == is used to compare the memory addresses of two objects, independent of what their equals() method says. == is even true for two null objects. I don’t want to imagine what happens if objects are allowed to override = assignment operator.
The answer to your question is rather simple: Backwards-compatibility means not changing the meaning of existing code. Since there is no existing code using user-defined operators, because user-defined operators do not exist, introducing them cannot possibly break backwards-compatibility. Foo a = new Foo(); Foo b = new Foo(); Foo c = a + b; Such code ...
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