T[new] misgivings

[Don]

Max Samukha wrote:
> On Thu, 15 Oct 2009 21:55:07 -0500, Andrei Alexandrescu
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> I talked to Walter about T[new] today and it seems we are having a 
>> disagreement.
> 
> I'd prefer Walter's way with a provision that array literals are
> immutable and allocated statically:
> 
> immutable(int)[] a = [1, 2, 3]; // no allocation here
> int[new] b = [1, 2]; // new storage is allocated and the literal is
> copied there
> int[] a = [1, 2, 3]; // error. dup needed
> auto c = [1, 2, 3]; // c is of type immutable(int)[]
> b[] = c; //b's length is changed and c's contents  copied to b's
> storage
> auto d = [1, 2, 3].dup; // d is of type int[new]
> auto e = [1, 2, 3].idup; // e is of type immutable(int)[new]
> 
> // arrays are true reference types
> int[new] a = [1, 2, 3];
> b = a;
> a.length = 22;
> assert (a.length == b.length);

This makes perfect sense to me. The rule would be:
If 'x' is T[new], then:
x = y; _always_ copies y into a {length, capacity-specified block}, 
unless it already is one. x is given a pointer to the start of that block.
x[] = y[]; does a memcpy, regardless of whether y is a T[new] or a T[].