Requiring all exceptions to be checked is evil. It leads to horrendous abstraction leakage (I need to let every caller know I use FooBarWidget in the core of my application??), improper error handling (just catch whatever comes out and move on so I don't have to declare it), or ubiquitous error wrapping (every class has a try...catch that turns the called exceptions into new exception types to throw).
Ironic that C++ is moving towards that as the Java community is moving away (by relying more on RuntimeException, which isn't checked).
> It leads to horrendous abstraction leakage (I need to let every caller know I use FooBarWidget in the core of my application??),
If your code catches any exceptions that might be thrown by its use of FooBarWidget, then you wouldn't need to specify it as an exception that your code might throw, right? If it doesn't, then your code exposes to callers that it uses FooBarWidget every time FooBarWidget throws an exception.
Ironic that C++ is moving towards that as the Java community is moving away (by relying more on RuntimeException, which isn't checked).