================
@@ -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));
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zygoloid wrote:
Instead of creating a single binding with a pack of values, I think template instantiation should be creating `N` `BindingDecl`s each with a single value, like we do when we instantiate a function parameter pack or a template parameter pack. I think that would simplify a lot of what you're doing here.
(During the initial parse, we should treat a structured binding declaration with a binding pack as being dependent, just like we treat a case where the initializer has an unexpanded pack as dependent.)
https://github.com/llvm/llvm-project/pull/121417