On 05/07/2014 12:07 PM, Yuriy wrote:
On Wednesday, 7 May 2014 at 09:51:01 UTC, John Colvin wrote:
On Wednesday, 7 May 2014 at 09:47:20 UTC, Yuriy wrote:
Hello, is there any way to static if(__ctfe)? I want to declare class
members which are only available in ctfe. Thanx.
Sadly not as far as I know. What's the use-case? There may be a nice
solution none-the-less.
Well, i'm currently playing with std.variant so it can be ctfe-friendly.
And it works pretty much, however i need to use T.stringof.ptr/length
instead of typeid (typeid is ctfeable), and i'm not sure if it's good
for performance in runtime. So for type comparison i'd like to compare
TypeInfos in rt, and T.stringof in ct. Using both with rt if will likely
generate more code.
I'd suggest to just look into making typeid's comparable in CTFE.
I have grepped around DMD's source code a little bit, but I am not
familiar with it. (And I don't want to get involved in DMD development,
because the code base is horrid.)
If you add in ctfeexpr.c/isCtfeComparable the conjunct 'x->op !=
TOKsymoff' (which probably is a very blunt way of enabling typeid
comparisons and should be done more precisely), then you will notice
that comparisons now work but always return 'false' for some types. I
have attempted a fix for this for classes as follows in typinf.c:
TypeInfoDeclaration *TypeClass::getTypeInfoDeclaration(){
if(!sym->vclassinfo){
if (sym->isInterfaceDeclaration())
return TypeInfoInterfaceDeclaration::create(this); // still buggy!
else{
sym->vclassinfo = TypeInfoClassDeclaration::create(this);
}
}
return sym->vclassinfo;
}
I.e. the problem is that the frontend always creates new
TypeInfoDeclarations instead of reusing a single existing one.
After this, typeid comparisons appear to work correctly for classes at
least.
You might look into getting this fixed completely for all types (or at
least file a bug containing the above information.)
