Why Are Interface Values in Go Not Addressable?

Non-addressability of Values in Interfaces in Go

The Go programming language ensures type safety by restricting the addressability of values stored in interfaces. This behavior differs from map values, as explained in the referenced discussion.

In the case of interfaces, values are not addressable due to design considerations that maintain type integrity. When a pointer to a value of type A is stored in an interface, it must remain valid even if a value of type B is subsequently stored in that interface.

Non-addressability prevents the accidental invalidation of pointers. Consider an example where an interface containing an int value has a pointer to that int. If a string value is later stored in the interface, the pointer to the int would become invalid.

The compiler enforces this design by prohibiting the passing of non-addressable values as receivers to methods with pointer receivers. This restriction prevents errors such as "type does not implement interface (method has pointer receiver)."

In summary, the non-addressability of values in interfaces is a crucial design decision that ensures type safety and prevents invalid pointer usage. It safeguards the integrity of interfaces by preventing accidental pointer invalidation when values of different types are stored within them. As a result, the compiler enforces this behavior by disallowing non-addressable values as receivers for methods with pointer receivers.

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