[dmd-internals] TemplateInstance <-> Identifier casts

[Walter Bright]

Yes, it's correct, although it's a hack.

Denis wrote:
> Hello, guys!
>
> I've noticed that DMD casts TemplateInstance to Identifier (and vice
> versa) in a few places and I doubt its correctness (since they are in
> no way related).
> It works in DMD (since pointer casts are unchecked in C++) but fails
> to do so in DDMD (resulting in a null pointer).
>
> Here is a simple snippet:
>
> Type *Parser::parseBasicType() {
> ...
> tid = new TypeIdentifier(loc, id);
> ...
> TemplateInstance *tempinst = new TemplateInstance(loc, id);
> tid->addIdent((Identifier *)tempinst);
> ...
> }
>
> here is another good one:
>
> void TypeQualified::syntaxCopyHelper(TypeQualified *t)
> {
>     //printf("TypeQualified::syntaxCopyHelper(%s) %s\n", t->toChars(),
> toChars());
>     idents.setDim(t->idents.dim);
>     for (int i = 0; i < idents.dim; i++)
>     {
> 	Identifier *id = (Identifier *)t->idents.data[i];
> 	if (id->dyncast() == DYNCAST_DSYMBOL)
> 	{
> 	    TemplateInstance *ti = (TemplateInstance *)id;
>
> 	    ti = (TemplateInstance *)ti->syntaxCopy(NULL);
> 	    id = (Identifier *)ti;
> 	}
> 	idents.data[i] = id;
>     }
> }
>
> I wonder how correct that is. It looks like TypeQualified.idents can
> store both Identifiers and TemplateInstances, but why put them into
> same bag? I believe there should either be 2 distinct methods
> (TypeQualified::addIdent/TypeQualified::addTemplateInstance) or just
> one that accepts generic Object. The former also helps getting rid of
> dyncast in syntaxCopyHelper, but the latter one is plain easier to
> implement.
>
> Any tip would be very appreciated, thanks!
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>