Re: is this a bug? opUnary!"++" Error: var has no effect

2012-02-08 Thread Timon Gehr 

On 02/09/2012 12:47 AM, Zach the Mystic wrote:

On 2/8/12 4:58 PM, Timon Gehr wrote:

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.


Is that because has.myArc.opUnary!"++"() is going to be ignored at that
level of compiler activity? The compiler demands only that __pitmp1481
has a value at that point?


This is the issue:

void main(){
int x;
++x, x; // error
}

While the whole expression has an effect, the single 'x' does not have 
an effect.





You may want to file a
bug report. For now, just using ++has.myArc; should work around the
issue.


http://d.puremagic.com/issues/show_bug.cgi?id=7467

Thanks, man. You're awesome!


You're welcome. =)

Re: is this a bug? opUnary!"++" Error: var has no effect

2012-02-08 Thread Zach the Mystic 

On 2/8/12 4:58 PM, Timon Gehr wrote:

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.


Is that because has.myArc.opUnary!"++"() is going to be ignored at that 
level of compiler activity? The compiler demands only that __pitmp1481 
has a value at that point?



You may want to file a
bug report. For now, just using ++has.myArc; should work around the issue.


http://d.puremagic.com/issues/show_bug.cgi?id=7467

Thanks, man. You're awesome!

Re: is this a bug? opUnary!"++" Error: var has no effect

2012-02-08 Thread Timon Gehr 

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.

is this a bug? opUnary!"++" Error: var has no effect

2012-02-08 Thread Zach the Mystic 
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