Bug 19633 – Identity expression produces wrong result with interface inheritance

https://dlang.org/spec/expression.html#identity_expressions says: "For class objects, identity is defined as the object references are for the same object. Null class objects can be compared with is." This is one option for comparing two interface references with `is`. Continuing on, there are other obviously inapplicable options, leaving just the default: "For other operand types, identity is defined as being the same as equality." This is another option. Test case: --- interface A {} interface B : A {} class C : A, B {} void main() { A a = new C; B b = cast(B)a; writeln(a is b); // false writeln(cast(Object)a is cast(Object)b); // true writeln(a == b); // true } --- If the first option is chosen, `a is b` should have the same result as `cast(Object)a is cast(Object)b`, which is true. If the second option is chosen, `a is b` should have the same result as `a == b`, which is true.

more comments and defunct PR in the newest report *** This issue has been marked as a duplicate of issue 23972 ***