Target typed new expressions for D?

[sighoya]

Relates to the following:

https://devblogs.microsoft.com/dotnet/welcome-to-c-9-0/#target-typed-new-expressions

What do you think about?

I like it more than `auto` inference. You have an explicit 
invariant, and the constructor takes the invariant into account 
for value construction.

I think, however, that using `new` in D isn't possible anymore, 
maybe some different keyword.

Is this at all possible with templates now or did we suffer from 
missing return type deduction?