[dmd-beta] rvalue references

[kenji hara]

2012年4月11日9:57 Walter Bright <walter at digitalmars.com>:
> *** Allow rvalue references, however, disallow any implicit conversions of
> the literal's type in the process of taking a reference to it. ***

It sounds good. After the changing, following code may work.

struct S {
    int val;
    bool opEquals(const ref S rhs) const { return val == rhs.val; }
}
void main() {
  S s1 = S(10);
  assert(S == S(10));
    // S(10) is rvalue but you can bind it with ref as *rvalue reference*.
}

> With all that, I intend to once again allow struct literals to be lvalues for 2.059.

But it sounds not good. We should keep all kind of literals (includinc
struct ones) as rvalue.

struct S {}
void f(    S s) { printf("receives rvalue\n"); }
void f(ref S s) { printf("receives lvalue\n"); }
viod main() {
  f(S());
    // if you revert struct literal to lvalue, this call matches both
ovarloads of f,
    // then causes ambiguous error.
}

> Somewhat later, also allow references to other literals like 0 and 5.6.

Agreed. Introducing *rvalue reference* requires such changes for consistency.
But, again, keep all literals rvalue, please.

Kenji Hara