Optional<unsigned> Sema::getFullyPackExpandedSize(TemplateArgument Arg) {
assert(Arg.containsUnexpandedParameterPack());
// If this is a substituted pack, grab that pack. If not, we don't know
// the size yet.
// FIXME: We could find a size in more cases by looking for a substituted
// pack anywhere within this argument, but that's not necessary in the common
// case for 'sizeof...(A)' handling.
TemplateArgument Pack;
switch (Arg.getKind()) {
case TemplateArgument::Type:
if (auto *Subst = Arg.getAsType()->getAs<SubstTemplateTypeParmPackType>())
Pack = Subst->getArgumentPack();
else
return None;
break;
case TemplateArgument::Expression:
if (auto *Subst =
dyn_cast<SubstNonTypeTemplateParmPackExpr>(Arg.getAsExpr()))
Pack = Subst->getArgumentPack();
else if (auto *Subst = dyn_cast<FunctionParmPackExpr>(Arg.getAsExpr())) {
for (ParmVarDecl *PD : *Subst)
if (PD->isParameterPack())
return None;
return Subst->getNumExpansions();
} else
return None;
break;
case TemplateArgument::Template:
if (SubstTemplateTemplateParmPackStorage *Subst =
Arg.getAsTemplate().getAsSubstTemplateTemplateParmPack())
Pack = Subst->getArgumentPack();
else
return None;
break;
case TemplateArgument::Declaration:
case TemplateArgument::NullPtr:
case TemplateArgument::TemplateExpansion:
case TemplateArgument::Integral:
case TemplateArgument::Pack:
case TemplateArgument::Null:
return None;
}
// Check that no argument in the pack is itself a pack expansion.
for (TemplateArgument Elem : Pack.pack_elements()) {
// There's no point recursing in this case; we would have already
// expanded this pack expansion into the enclosing pack if we could.
if (Elem.isPackExpansion())
return None;
}
return Pack.pack_size();
}
