vanish single tuple on lowering verification

Author: omochi

lib/SIL/IR/TypeLowering.cpp

@@ -3012,6 +3012,9 @@ bool TypeConverter::visitAggregateLeaves(
     std::optional<unsigned> index;
     std::tie(ty, origTy, field, index) = popFromWorklist();
     assert(!field || !index && "both field and index!?");
+    if (auto origEltTy = origTy.getVanishingTupleElementPatternType()) {
+      origTy = *origEltTy;
+    }
     if (isAggregate(ty) && !isLeafAggregate(ty, origTy, field, index)) {
       if (auto packTy = dyn_cast<SILPackType>(ty)) {
         for (auto packIndex : indices(packTy->getElementTypes())) {

test/IRGen/variadic_generic_types.swift

@@ -31,3 +31,9 @@ blackHole(G<Int, String>.self)
 let g = G<Int, String, Float>()
 blackHole(g.makeTuple1())
 blackHole(g.makeTuple2())
+
+struct VariadicOptionalTuple<each V> {
+    var v: (repeat (each V)?)
+}
+
+func useVOT(_: VariadicOptionalTuple<String>) {}