On 02/08/2012 10:48 PM, Zach the Mystic wrote:
My goal is to be able to overload the "++" operator transparently to the
code, but I can't.
import std.stdio;
struct Arc {
int I = 0;
// This is void, but the error appears under all return types
void opUnary(string op)() if( op == "++" ) {
++I;
}
}
struct HasArc {
Arc myArc;
}
void main() {
HasArc has;
writefln(" Arc.I = %s", has.myArc.I); // Arc.I = 0
has.myArc++; // Error: var has no effect in expression (__pitmp1481)
// Okay, try this instead:
auto UselessVar = has.myArc++; // Works fine
writefln(" Arc.I = %s", has.myArc.I); // Arc.I = 1
}
Obviously the expression has an effect. Bug? If not, what is the right
way to have the "++" operator pass that error test?
Thanks, Zach
This is indeed a bug.
The expression is rewritten internally into (pseudo code)
(auto __pitmp1481 = has.myArc, has.myArc.opUnary!"++"(), __pitmp1481);
This introduces a sub-expression with no effect. You may want to file a
bug report. For now, just using ++has.myArc; should work around the issue.
