[SIL] Look through optionals in an unowned type's referent type during type classification (swiftlang#32949)

Author: theblixguy

lib/SIL/IR/TypeLowering.cpp

@@ -390,7 +390,8 @@ namespace {
     } \
     RetTy visit##Name##StorageType(Can##Name##StorageType type, \
                                    AbstractionPattern origType) { \
-      auto referentType = type->getReferentType(); \
+      auto referentType = \
+        type->getReferentType()->lookThroughSingleOptionalType(); \
       auto concreteType = getConcreteReferenceStorageReferent(referentType); \
       if (Name##StorageType::get(concreteType, TC.Context) \
             ->isLoadable(Expansion.getResilienceExpansion())) { \

test/SILGen/unowned.swift

@@ -161,8 +161,13 @@ func takesUnownedStruct(_ z: Unowned<C>) {}
 // Make sure we don't crash here
 struct UnownedGenericCapture<T : AnyObject> {
   var object: T
+  var optionalObject: T?
 
   func f() -> () -> () {
     return { [unowned object] in _ = object }
   }
+
+  func g() -> () -> () {
+    return { [unowned optionalObject] in _ = optionalObject }
+  }
 }