Current sentiment on Nullable.get

[Neia Neutuladh]

On Sat, 15 Dec 2018 03:01:18 +0000, Rubn wrote:
> On Saturday, 15 December 2018 at 02:14:15 UTC, Jonathan M Davis wrote:
>> n = value;
>> foo(n.get);
> 
> Why wouldn't you just do
> 
> foo( value );
> 
> then ? If you know the value isn't going to be null then you shouldn't
> be using nullable.

You don't know that cast(Object)null is an invalid value. You need to 
check whether you currently have a valid value. So you create a wrapper 
struct that has a sentry value. You know for certain that that sentry 
value doesn't conflict with anything the user might want to use (unlike, 
say, T.init).

This lets you organize your code in a nicer way when you have complex 
initialization, or when you need to de-initialize a value.

I mentioned it in the named arguments thread as a way to check whether all 
required parameters to a function were provided via an argument struct. 
Whether explicitly passing null is valid or not depends on the function, 
and the Invoker wrapper can't make that call. Whether an argument must be 
provided depends on the function signature alone. So the Invoker wrapper 
could use Nullable to distinguish between an argument that is absent and 
an argument that is present and equal to its type's .init value.