Eliminate redundancy of dup/idup

[Daniel Murphy]

"kenji hara" <k.hara.pg at gmail.com> wrote in message 
news:mailman.1679.1347204757.31962.digitalmars-d at puremagic.com...
> I've posted two pull requests for the purpose.
>
> https://github.com/D-Programming-Language/dmd/pull/1110
> https://github.com/D-Programming-Language/druntime/pull/298
>
> inout parameter and strongly purity function can realize this.
>

This is great.  Is there any chance a similar method could be applied to 
give '~' and 'new' the same strong-purity benefits?  This is much cleaner 
than introducing expression-level purity.