Re: Express "Class argument may not be null" ?

[Steven Schveighoffer via Digitalmars-d-learn]

On 8/8/17 2:56 PM, ag0aep6g wrote:
On 08/08/2017 08:34 PM, Johan Engelen wrote:
   How would you express the function interface intent that a 
reference to a class may not be null?
For a function "void foo(Klass)", calling "foo(null)" is valid. How do 
I express that that is invalid? (let's leave erroring with a compile 
error aside for now)

Something equivalent to C++'s pass by reference: "void foo(Klass&)".
[snip]

But you can pass null in a ref parameter:

----
void f(ref int x) @safe {}
void main() @safe
{
     int* p = null;
     f(*p);
}
----

Note that C++ also can do this, so I'm not sure the & is accomplishing 
the correct goal:

void foo(Klass&);

int main()
{
   Klass *k = NULL;
   foo(*k);
}

However, the in contract does actually enforce the requirement.

-Steve