On 04/03/2018 04:26 PM, ag0aep6g wrote:
On 04/03/2018 05:13 PM, Steven Schveighoffer wrote:
Unfortunately, I found out that it's not just "pre-filled with some
values". Member postblits are run before the containing postblit.
https://run.dlang.io/is/mt6eGa
So this means, the data that is available to the postblit has already
been processed.
There's a similar situation with constructors: A constructor can call
another constructor, which can lead to double initialization of fields.
Example:
----
class C
{
int x;
this() immutable
{
this(42); /* Initializes x. */
x = 13; /* Breaking immutable, or ok? */
}
this(int x) immutable
{
this.x = x;
}
}
----
Let's replace "int" with an UDT:
struct S
{
int x = -1;
this(int y) immutable { x = y; }
void opAssign(int) immutable;
}
class C
{
S x;
this() immutable
{
this(42); /* Initializes x. */
x = 13; /* Breaking immutable, or ok? */
}
this(int x) immutable
{
this.x = x;
}
}
This code compiles, and calls the constructor twice for the same object.
Clearly that shouldn't be allowed to pass. I've submitted
https://issues.dlang.org/show_bug.cgi?id=18719 - thanks! (The problem
seems to occur even without immutable, it's endemic to forwarding
constructors.)
Andre
