================
@@ -951,28 +959,124 @@ Sema::ActOnDecompositionDeclarator(Scope *S, Declarator
&D,
return New;
}
+// CheckBindingsCount
+// - Checks the arity of the structured bindings
+// - Creates the resolved pack expr if there is
+// one
+static bool CheckBindingsCount(Sema &S, DecompositionDecl *DD,
+ QualType DecompType,
+ ArrayRef<BindingDecl *> Bindings,
+ unsigned MemberCount) {
+ auto BindingWithPackItr =
+ std::find_if(Bindings.begin(), Bindings.end(),
+ [](BindingDecl *D) -> bool { return D->isParameterPack();
});
+ bool HasPack = BindingWithPackItr != Bindings.end();
+ bool IsValid;
+ if (!HasPack) {
+ IsValid = Bindings.size() == MemberCount;
+ } else {
+ // there may not be more members than non-pack bindings
+ IsValid = MemberCount >= Bindings.size() - 1;
+ }
+
+ if (IsValid && HasPack) {
+ // create the pack expr and assign it to the binding
+ unsigned PackSize = MemberCount - Bindings.size() + 1;
+ QualType PackType = S.Context.getPackExpansionType(
+ S.Context.DependentTy, std::nullopt, /*ExpectsPackInType=*/false);
+ BindingDecl *BD = (*BindingWithPackItr);
+ BD->setBinding(PackType,
+ ResolvedUnexpandedPackExpr::Create(
+ S.Context, DD->getBeginLoc(), DecompType, PackSize));
----------------
ricejasonf wrote:
The problem is that we do not know the length of the pack until the initializer
expression is created. This happens in various locations depending on context
such as range based for loops. I am not saying it isn't possible, but I think
it would require creating the init expression up front which I do not know if
that would be problematic with how variables are checked. We could also do
Bindings in a separate allocation, but that would require keeping the
DecompositionDeclarator around somehow, and there would need to be that extra
information in the DecompositionDecl which would have a cost for Decomps that
do not have a pack. (I don't know if that is an issue.)
https://github.com/llvm/llvm-project/pull/121417
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