Understanding opAssign and 'alias this'
John Colvin
john.loughran.colvin at gmail.com
Mon Oct 14 02:17:11 PDT 2013
On Sunday, 13 October 2013 at 21:37:31 UTC, Maurice wrote:
> Hello,
>
> Can anybody explain my what is happening here?
>
> enum xxx = true;
>
> struct A {
> static if (xxx) ref A opAssign(ref const A a) { return this; }
> ref A opAssign(int v) { return this; }
> }
>
> struct B {
> A a;
> alias a this;
> }
>
> void main() {
> A a;
> B b;
> a = b; // [1]
> b = a; // [2]
> }
>
> When xxx is false:
> [1] Gives an error
> [2] Compiles fine
>
> When xxx is true:
> [1] Compiles fine
> [2] Gives an error
>
> What exactly is happening here? When xxx is false, what does 'b
> = a' do that is wrong when xxx is true?
>
> I can't find any clear documentation about opAssign and its
> 'default' implementation.
>
> Thanks!
>
> -Maurice-
Everything is working fine except for the error on [2] when xxx
== true, which I think is a bug.
minimised test:
struct A
{
void opAssign(A a) {}
}
struct B {
A a;
alias a this;
}
void main() {
A a;
B b;
b = a;
}
Error: function assign.B.opAssign (B p) is not callable using
argument types (A)
More information about the Digitalmars-d-learn
mailing list