tell me about type erasure

Type erasure in Swift is a technique used to abstract away the specific type information of a value, allowing you to work with values of different types in a uniform way. This is particularly useful when dealing with protocols and generics.

In the context of error handling, type erasure is used when thrown errors are type erased and appear with the Any error type in the catch handler. This means that the concrete type information of the error is lost, and you may need to insert a dynamic type check if you want to handle the error exhaustively. This process involves boxing and unboxing, which can be challenging in highly constrained systems without runtime allocation capabilities.

However, Swift 6 introduces "type throws" to overcome this limitation. With type throws, you can specify the error type along with the throws keyword, eliminating the need for type erasure. The error appears in the catch block with its concrete type, allowing for more precise error handling without the need for dynamic type checks.

For more details, you can refer to the session What’s new in Swift (23:21).

Relevant Sessions

1. What’s new in Swift
2. Explore Swift performance
3. Consume noncopyable types in Swift