How Can Type Assertion Handle Unknown Interfaces in Go?

Type Assertion for Unknown Interfaces in Go

Type assertions in Go allow type conversion from an interface to a specific type. However, what happens if the type of the interface is unknown beforehand?

Understanding Type Assertion

As demonstrated in the given code, type assertion involves obtaining an object's value via reflection and then using type assertion to retrieve the actual object:

obj := new(User)
out := reflect.ValueOf(obj).Elem().Interface().(User)
fmt.Println(out == *obj) // true

Type Assertion with Unknown Types

In the provided function, Foo, the type of the passed object is unknown. To perform type assertion, we need to know the static type that the interface value should be checked against. This is not possible without knowing the specific type.

The Limitation

Type assertions require knowledge of the static type at compile-time to enforce type safety. As interface types are not statically checked, it becomes impossible to determine the specific type to check against dynamically.

Consequences

The consequence of not knowing the specific type is that the compiler cannot write the necessary type check at runtime. This guarantees that any potential assignment would only occur if the types match up, preserving type safety.

Conclusion

Type assertion for unknown interfaces is not possible in Go due to the inherent nature of type checking. Type assertions rely on the compiler's ability to verify types statically, which is not feasible when dealing with interfaces of unknown types.

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