SIL: Fix type lowering of 'unowned T' where 'T' is a type parameter

The abstraction pattern's generic signature does not describe
the substituted type, and it may not be present at all.

Fixes #79244.

Author: slavapestov

lib/SIL/IR/TypeLowering.cpp

@@ -655,19 +655,29 @@ namespace {
       return visitAbstractTypeParamType(type, origType, isSensitive);
     }
 
-    Type getConcreteReferenceStorageReferent(Type type,
+    Type getConcreteReferenceStorageReferent(Type substType,
                                              AbstractionPattern origType) {
-      if (type->isTypeParameter()) {
-        auto genericSig = origType.getGenericSignature();
-        if (auto concreteType = genericSig->getConcreteType(type))
-          return concreteType;
-        if (auto superclassType = genericSig->getSuperclassBound(type))
-          return superclassType;
-        assert(genericSig->requiresClass(type));
+      substType = substType->getReferenceStorageReferent();
+      origType = origType.getReferenceStorageReferentType();
+
+      if (auto objectType = substType->getOptionalObjectType()) {
+        substType = objectType;
+        origType = origType.getOptionalObjectType();
+      }
+
+      if (substType->isTypeParameter()) {
+        if (auto genericSig = origType.getGenericSignature()) {
+          auto type = origType.getType();
+          if (auto concreteType = genericSig->getConcreteType(type))
+            return concreteType;
+          if (auto superclassType = genericSig->getSuperclassBound(type))
+            return superclassType;
+          assert(genericSig->requiresClass(type));
+        }
         return TC.Context.getAnyObjectType();
       }
 
-      return type;
+      return substType;
     }
 
 #define NEVER_LOADABLE_CHECKED_REF_STORAGE(Name, ...) \
@@ -710,9 +720,7 @@ namespace {
     RetTy visit##Name##StorageType(Can##Name##StorageType type, \
                                    AbstractionPattern origType, \
                                    IsTypeExpansionSensitive_t isSensitive) { \
-      auto referentType = \
-        type->getReferentType()->lookThroughSingleOptionalType(); \
-      auto concreteType = getConcreteReferenceStorageReferent(referentType, origType); \
+      auto concreteType = getConcreteReferenceStorageReferent(type, origType); \
       if (Name##StorageType::get(concreteType, TC.Context) \
             ->isLoadable(Expansion.getResilienceExpansion())) { \
         return asImpl().visitLoadable##Name##StorageType(type, origType, \

test/SILGen/unowned-class-bound-generic-parameter.swift

@@ -20,4 +20,18 @@ func makeGenericClosureWithNativeClass2<T>(t: T) where T : ClassProtocol, T : Ba
   _ = { [unowned t] in _ = t }
 }
 
-// CHECK-LABEL: sil private [ossa] @$s4main34makeGenericClosureWithNativeClass21tyx_tAA9BaseClassCRbzAA0I8ProtocolRzlFyycfU_ : $@convention(thin) <T where T : BaseClass, T : ClassProtocol> (@guaranteed @sil_unowned T) -> () {
+// CHECK-LABEL: sil private [ossa] @$s4main34makeGenericClosureWithNativeClass21tyx_tAA9BaseClassCRbzAA0I8ProtocolRzlFyycfU_ : $@convention(thin) <T where T : BaseClass, T : ClassProtocol> (@guaranteed @sil_unowned T) -> () {
+
+// https://github.com/swiftlang/swift/issues/79244
+
+struct Wrapper<T: AnyObject> {
+  unowned var t: T
+}
+
+func f1<T: AnyObject>(t: T) {
+  _ = { Wrapper(t: t) }
+}
+
+func f2<T: AnyObject, U: AnyObject>(u: U, tt: Array<Wrapper<T>>) {
+  _ = tt.map { _ in Wrapper(t: u) }
+}