Merge pull request #82043 from nate-chandler/rdar152580661

[TypeLowering] Record pack used in aggregate signature.

Author: nate-chandler

lib/SIL/IR/TypeLowering.cpp

@@ -2733,6 +2733,7 @@ namespace {
     template <class LoadableLoweringClass>
     TypeLowering *handleAggregateByProperties(CanType type,
                                               RecursiveProperties props) {
+      props = mergeHasPack(HasPack_t(type->hasAnyPack()), props);
       if (props.isAddressOnly()) {
         return handleAddressOnly(type, props);
       }

validation-test/IRGen/rdar152580661.swift

@@ -0,0 +1,14 @@
+// RUN: %target-swift-frontend %s -target %target-swift-5.9-abi-triple -emit-ir
+
+struct H<T> {
+  var packs: [Pack<T>] {
+      id(_packs)
+  }
+  let _packs: [Pack<T>]
+}
+
+struct Pack<each T> {}
+
+func id<T>(_ t: T) -> T {
+  return t
+}