On 6/20/11 7:14 AM, kenji hara wrote:
I have tried to conversion test.
----
import std.conv;
void main()
{
tests1();
tests2();
testc1();
testc2();
}
struct SS1{ ST1 opCast(T:ST1)(){ return ST1(); } }
struct ST1{ }
void tests1()
{
SS1 s1;
auto t1a = cast(ST1)(s1); // -> s1.opCast!ST1()
// auto t1b = to!ST1(s1); // NG
}
struct SS2{ }
struct ST2{ this(SS2 source){} }
void tests2()
{
SS2 s2;
auto t2a = cast(ST2)(s2); // -> ST2(s2) == ctor call
// auto t2b = to!ST2(s2); // NG
}
class CS1{ CT1 opCast(T:CT1)(){ return new CT1(); } }
class CT1{ }
void testc1()
{
CS1 s1 = new CS1();
auto t1a = cast(CT1)(s1); // -> s1.opCast!CT1()
auto t1b = to!CT1(s1);
// T toImpl(T, S)(S value) if (is(S : Object)&& is(T : Object))
// -> cast(CT1)(s1)
// -> s1.opCast!CT1()
}
class CS2{ }
class CT2{ static CT2 opCall(CS2 source){ return new CT2(); } }
//class CT2{ this(CS2 source){} } // Unfortunately, ctor is not
called by CastExp.
void testc2()
{
CS2 s2 = new CS2();
auto t2a = cast(CT2)(s2); // -> CT2(s2) == CT2.opCall(s2)
// auto t2b = to!CT2(s2); // compiled, but runtime error occurs
// T toImpl(T, S)(S value) if (is(S : Object)&& is(T : Object))
// -> cast(CT1)(s1)
// -> null
}
----
Some of thoughts of me:
1. std.conv.to should support built-in casting behavior, at least on
struct object.
This feature was recently fixed. See bug5897.
Agreed. I simply forgot about that.
2. Using to!T() member function by std.conv.to is unnecessary feature,
because it can be replaced by opCast!T.
I think that's fine too.
3. For class object, I guess that is need to support 'Conversion
Interface that Intrude into TargetType'.
I think 'conversion constructor call' is good fit to it.
Not sure I understand that.
Kenji, you may want to package your 1 and 2 into a pull request, and 3
in a separate pull request so we all can take a look.
Thanks,
Andrei
