Wishlist proposal, documenting fn arg as in or out or mod

[Cecil Ward]

I would love to be able to document my arguments as in or out but 
also as read-write (like var in pascal, like fortran (?) and C++ 
D ref.

We already have "in". Good thing.

However it has got mixed up with const so that you can’t declare 
something as both. Is that right? I would like the compilers not 
to complain if something is declared as "in const" as there are 
two independent _intentions_ here, even though of course in 
implies const. Apart from that in is great. I use it everywhere. 
Small tweak.

Out is perfect as is.

However I hate using ref for input-output arguments as it isn’t 
visible at the call site and a ref could be just 
ref-for-implementation as in where you want to pass by reference 
to avoid copying a large object, but that has nothing to do with 
documenting the intention behind the in / out marking of the arg. 
Leave ref as it is for those who like it.

So I propose a new keyword either something like modified or mod 
or rw or input_output. Beauty contest, I don’t care what wins. 
(Shame inout is already taken.)

So my fn might look like

void myfn( in T1 InputArg, in const ref InputArray1, rw Modify, 
out result )

What do you think?

Then D would be as good as Ada in this respect, if I can remember 
from 40 years ago. ;-)