[TBDGen] The non-deallocating destructor applies to some @objc classes.

The non-deallocating destructor doesn't exists when dealloc can be overriden,
which means any class that inherits from a class defined in Objective-C. This
isn't necessarily all @objc classes, because of the
-disable-objc-attr-requires-foundation-module flag.

Fixes rdar://problem/40542246.

Author: huonw

lib/TBDGen/TBDGen.cpp

@@ -24,8 +24,9 @@
 #include "swift/IRGen/Linking.h"
 #include "swift/SIL/FormalLinkage.h"
 #include "swift/SIL/SILDeclRef.h"
-#include "swift/SIL/SILWitnessTable.h"
+#include "swift/SIL/SILModule.h"
 #include "swift/SIL/SILVTableVisitor.h"
+#include "swift/SIL/SILWitnessTable.h"
 #include "swift/SIL/TypeLowering.h"
 #include "llvm/ADT/StringSet.h"
 
@@ -233,13 +234,6 @@ void TBDGenVisitor::visitClassDecl(ClassDecl *CD) {
     auto hasFieldOffset = var && var->hasStorage() && !var->isStatic();
     if (hasFieldOffset)
       addSymbol(LinkEntity::forFieldOffset(var));
-
-    // The non-allocating forms of the destructors.
-    if (auto dtor = dyn_cast<DestructorDecl>(value)) {
-      // ObjC classes don't have a symbol for their destructor.
-      if (!isObjC)
-        addSymbol(SILDeclRef(dtor, SILDeclRef::Kind::Destroyer));
-    }
   }
 
   visitNominalTypeDecl(CD);
@@ -300,6 +294,19 @@ void TBDGenVisitor::visitConstructorDecl(ConstructorDecl *CD) {
   visitAbstractFunctionDecl(CD);
 }
 
+void TBDGenVisitor::visitDestructorDecl(DestructorDecl *DD) {
+  // Class destructors come in two forms (deallocating and non-deallocating),
+  // like constructors above. This is the deallocating one:
+  visitAbstractFunctionDecl(DD);
+
+  auto parentClass = DD->getParent()->getAsClassOrClassExtensionContext();
+
+  // But the non-deallocating one doesn't apply to some @objc classes.
+  if (!Lowering::usesObjCAllocator(parentClass)) {
+    addSymbol(SILDeclRef(DD, SILDeclRef::Kind::Destroyer));
+  }
+}
+
 void TBDGenVisitor::visitExtensionDecl(ExtensionDecl *ED) {
   if (!ED->getExtendedType()->isExistentialType()) {
     addConformances(ED);

lib/TBDGen/TBDGenVisitor.h

@@ -102,6 +102,8 @@ class TBDGenVisitor : public ASTVisitor<TBDGenVisitor> {
 
   void visitConstructorDecl(ConstructorDecl *CD);
 
+  void visitDestructorDecl(DestructorDecl *DD);
+
   void visitExtensionDecl(ExtensionDecl *ED);
 
   void visitProtocolDecl(ProtocolDecl *PD);

test/TBD/class_objc.swift

@@ -0,0 +1,37 @@
+// RUN: %empty-directory(%t)
+// RUN: %gyb %s > %t/main.swift
+
+// RUN: %target-swift-frontend -emit-ir -o- -parse-as-library -module-name test -import-objc-header %S/Inputs/objc_class_header.h -validate-tbd-against-ir=all %t/main.swift -disable-objc-attr-requires-foundation-module
+
+// RUN: %target-swift-frontend -enable-resilience -emit-ir -o- -parse-as-library -module-name test -import-objc-header %S/Inputs/objc_class_header.h -validate-tbd-against-ir=all %t/main.swift -disable-objc-attr-requires-foundation-module
+
+// REQUIRES: objc_interop
+
+import Foundation
+
+% names = ["Public", "Internal", "Private"]
+
+% for i, name in enumerate(names):
+% access = name.lower()
+
+// a class by itself
+${access} class ${name}Empty: NSObject {}
+
+// subclasses of that
+% for subname in names[i:]:
+% subaccess = subname.lower()
+${subaccess} class ${subname}Sub${name}Empty: ${name}Empty {}
+%end
+
+${access} class ${name}InheritObjCProtocol: NSObject, ObjCProtocol {}
+
+// some bugs were revealed when there's @objc without inheriting from
+// NSObject.
+@objc ${access} class ${name}ObjCOnly {}
+
+%end
+
+@usableFromInline
+@objc
+internal class InternalObjCOnlyUsableFromInline {}
+