I get a compiler error under v.0.138 when I try to cast a template object to its parent interface when passing it to the delegate argument of opApply.  The workaround forces me to store the cast to a temporary variable, then pass the temporary to the opApply delegate.

------------
private import std.stdio;

interface Foo {
    void foo();
}

class GenericFoo(T) : Foo {
    T* value;
    void foo() {
        writefln("GenericFoo!(%s).foo()", (typeid(T)).toString());
    }
}

class FooArray {
    GenericFoo!(int) gf;

    this() { gf = new GenericFoo!(int); }

    int opApply(int delegate(inout Foo) dg){
        int result = 0;
        for (int i = 0; i < 5; i++) {
            gf.value = &i;
            //result = dg(gf); // Error: cast(Foo)(gf) not an lvalue
            //result = dg(cast(Foo)gf);   // Error: ditto
            //result = dg((cast(Foo)gf)); // Error: ditto
            Foo f = cast(Foo)gf; // Workaround
            result = dg(f);      // Ok
            if (result) break;
        }
        return result;
    }
}

int main(char[][] args) {
    FooArray fa = new FooArray;
    foreach (Foo f; fa) f.foo();
    return 0;
}

------------

I suspect this test case may be generalized further, but I'm not sure how to go about simplifying it.  Any help would be appreciated.

Regards,
Garett

Garett Bass escribió:
> I get a compiler error under v.0.138 when I try to cast a template object to its parent interface when passing it to the delegate argument of opApply.  The workaround forces me to store the cast to a temporary variable, then pass the temporary to the opApply delegate.
> 
> ------------
<snip>
> ------------
> 
> I suspect this test case may be generalized further, but I'm not sure how to go about simplifying it.  Any help would be appreciated.
> 
> Regards,
> Garett 
> 
> 

Here's a reduced version:

void foo(inout int i) {}

void main()
{
        long l;
        foo(l); //6
}

With gdc 0.16, I get: "foo.d:6: cast(int)(l) is not an lvalue". There've been times when allowing this has beed asked, but in the end, I think it's somewhat understandable behavior.

-- 
Carlos Santander Bernal

Garett Bass schrieb am 2005-11-11:
> I get a compiler error under v.0.138 when I try to cast a template object to its parent interface when passing it to the delegate argument of opApply.  The workaround forces me to store the cast to a temporary variable, then pass the temporary to the opApply delegate.
>
> ------------
> private import std.stdio;
>
> interface Foo {
>     void foo();
> }
>
> class GenericFoo(T) : Foo {
>     T* value;
>     void foo() {
>         writefln("GenericFoo!(%s).foo()", (typeid(T)).toString());
>     }
> }
>
> class FooArray {
>     GenericFoo!(int) gf;
>
>     this() { gf = new GenericFoo!(int); }
>
>     int opApply(int delegate(inout Foo) dg){
>         int result = 0;
>         for (int i = 0; i < 5; i++) {
>             gf.value = &i;
>             //result = dg(gf); // Error: cast(Foo)(gf) not an lvalue
>             //result = dg(cast(Foo)gf);   // Error: ditto
>             //result = dg((cast(Foo)gf)); // Error: ditto
>             Foo f = cast(Foo)gf; // Workaround
>             result = dg(f);      // Ok
>             if (result) break;
>         }
>         return result;
>     }
> }
>
> int main(char[][] args) {
>     FooArray fa = new FooArray;
>     foreach (Foo f; fa) f.foo();
>     return 0;
> }
>
> ------------
>
> I suspect this test case may be generalized further, but I'm not sure how to go about simplifying it.  Any help would be appreciated.

Added to DStress as http://dstress.kuehne.cn/nocompile/i/inout_01.d

Thomas