Can the compiler automatically declare a class as final during compilation?

The Swift compiler does not automatically declare classes as final. A class becomes final only if the developer explicitly specifies the final modifier.

The final modifier prevents inheritance from the class, allowing the compiler to optimize method calls and improve performance.

However, the compiler does not analyze the code to independently determine whether a class can be made final, and does not change its declaration. It is the developer's responsibility to explicitly mark classes as final if they are not intended for inheritance.

Example:

final class MyClass {
    // This class cannot be inherited
}

class AnotherClass {
    // This class can be inherited
}

If a class is not marked as final, it is considered open for inheritance by default (unless open or public with different access rules are specified).