DIP 1021--Argument Ownership and Function Calls--Community Review Round 1

[rikki cattermole]

I had written up a comment all about the DIP.
And then I reread it.

This line seems to be very important and I missed it the first time: 
"The checks would only be enforced for @safe code.".

If the semantics are indeed only valid in @safe code, the single example 
in the DIP does not show this to be the case.

It would be nice to have some pseudo-code based rules like the Rust one.
Just to make it clear in addition to some worked examples as to what is 
going on valid/invalid wise and how it ties into DIP25 and DIP1000.