[Issue 9062] AddrExp should distinguish the existence of property resolution.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9062



--- Comment #14 from Kenji Hara <k.hara.pg at gmail.com> 2012-12-05 16:26:04 PST ---
(In reply to comment #13)
> C++ has one special case where (e) means something different from e. (Few
> people know  that case exists.)
> 
> Adding such to D makes me very nervous. I think it's a sound principle that any
> expression can be parenthesized without altering its meaning, it's important
> for anything that generates source code (like mixins are wont to do).

It's sure. But, &propfunc is one of the key point for the more property
enforcement.

- If &propfunc returns an address of returned value, all function related meta
templates will be broken (e.g. FunctionTypeOf).
- If &propfunc returns a function pointer of propfunc, all semantics are kept
intact. But, to get an address of returned value from propfunc will become
impossible in range of using built-in-language features.

I have thought a library solution, but this is ugly to me.

import std.algorithm : move;
    T identity(T)(    T t) { return move(t); }
ref T identity(T)(ref T t) { return t; }

int g;
@property ref int propfunc() { return g; }
void main() {
    auto p1 = &propfunc;            // p1 is function pointer
    auto p2 = &identity(propfunc);  // p2 is int*
    // identity(propfunc) makes an expression,
    // then getting an address of returned value can be succeeded.
    assert(p2 == &g);
}

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