[Issue 2073] Variant.coerce!() fails
https://issues.dlang.org/show_bug.cgi?id=2073 Andrei Alexandrescu changed: What|Removed |Added Version|2.014 |D2 --
[Issue 2073] Variant.coerce!() fails
http://d.puremagic.com/issues/show_bug.cgi?id=2073 Andrei Alexandrescu changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED --- Comment #3 from Andrei Alexandrescu 2010-09-25 21:48:13 PDT --- Fixed in http://www.dsource.org/projects/phobos/changeset/2049 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
[Issue 2073] Variant.coerce!() fails
http://d.puremagic.com/issues/show_bug.cgi?id=2073
--- Comment #2 from Michael Rynn 2010-02-06 19:43:37 PST
---
Plus once we get a valid object , an extra template is needed in std.conv for
interfaces for the Interface coercion to work, just like the Object-to-Object
For std.conv
/**
Object-to-interface conversions throw exception when the source is
non-null and the target is null.
*/
T to(T, S)(S value) if (is(S : Object) && is(T == interface))
{
auto result = cast(T) value;
if (!result && value)
{
throw new ConvError("Cannot convert object of static type "
~S.classinfo.name~" and dynamic type "~value.classinfo.name
~" to type "~T.classinfo.name);
}
return result;
}
And it would be nice for the unittest to reflect the increased capability.
unittest {
interface A {}
interface Z {}
interface B : A {}
class C : B {}
class D : C {}
class E : Z {}
string K = "123";
Variant vn1 = K;
int n1 = vn1.coerce!(int);
assert(n1 == 123, "failed string to number coercion");
A a = new D;
Z x = new E;
Variant v2 = a;
//B b = v2.coerce!(B);
C c = cast(C) a;
a = v2.coerce!(A);
c = v2.coerce!(C);
D d = v2.coerce!(D);
try {
x = v2.coerce!(Z);
}
catch( std.conv.ConvError ce)
{
//writeln("Convert error");
x = null;
}
assert(x is null, "invalid coercion");
}
Issues.
Should interface ref back to object ref be allowed?
Should there be a facility to do this from a "generic" interface pointer.
Attempts to do it using higher level cast thingos failed.
There is no generic cast(Interface) like cast(Object), and we know the pointers
are not the same sort of thing.
How about something like eg, interface().toObject ?, instead of exposing
the icky pointer internals. (Also object.d and cast_.d seem to differ on how
it is done. cast.d looks like it needs a makeover)
Such a facility implicitly exists to get a this reference into every interface
virtual method call.
Having to know about TypeInfo_Class and TypeInfo_Interface, and Interface*
offsets is icky.
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[Issue 2073] Variant.coerce!() fails
http://d.puremagic.com/issues/show_bug.cgi?id=2073
Michael Rynn changed:
What|Removed |Added
CC||y0uf00...@gmail.com
--- Comment #1 from Michael Rynn 2010-02-06 19:27:01 PST
---
I looked at coerce because I was trying to make the std.variant pass some of
the tango.core.Variant unit tests.
coerce needs runtime type checking, and must thereby incur a small runtime
penalty.
As well as the this, there is a failure of cast coercions for object and
interface.
T coerce(T)()
{
// coerce is awkward because it also depends on the runtime type
static string coerceMsg(TypeInfo t1, TypeInfo t2)
{
return format("Coerce from %s to %s", t1.toString, t2.toString);
}
static if (isNumeric!(T))
{
// coercive conversions will have a time penalty
if (type == typeid(immutable(char)[]))
{
return to!(T)(*cast(string*)&store);
}
// also do wstring and dstring ?
return to!(T)(get!(real));
}
else static if( is(T : Object) )
{
if (cast(TypeInfo_Class)type)
{
return to!(T) (( *cast(Object*) &store ));
}
if (cast(TypeInfo_Interface)type)
{
// ugly magic borrowed from object.d, to get the original
object and recast
// why is there no direct facility for this? like
interface.objectof property?
// the not quite the same ugliness in _d_toObject in cast_.d
does not work
void* p = &store;
Interface* pi = **cast(Interface ***)*cast(void**)p;
Object o = cast(Object)(*cast(void**)p - pi.offset);
return to!(T)(o);
}
throw new VariantException(coerceMsg(type, typeid(T)));
}
else static if (is (T == interface ))
{
if (cast(TypeInfo_Class)type)
{
return to!(T) (( *cast(Object*) &store ));
}
if (cast(TypeInfo_Interface)type)
{
void* p = &store;
Interface* pi = **cast(Interface ***)*cast(void**)p;
Object o = cast(Object)(*cast(void**)p - pi.offset);
return to!(T)(o);
}
throw new VariantException(coerceMsg(type, typeid(T)));
}
else static if (isSomeString!(T))
{
return to!(T)(toString);
}
else
{
// Fix for bug 1649
static assert(false, "unsupported type for coercion");
}
}
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[Issue 2073] Variant.coerce!() fails
http://d.puremagic.com/issues/show_bug.cgi?id=2073 Andrei Alexandrescu changed: What|Removed |Added Status|NEW |ASSIGNED CC||and...@metalanguage.com AssignedTo|nob...@puremagic.com|and...@metalanguage.com -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
