[SILGen] Don't SILGen an @objc entry point for a deinit with no body (#19472)

In general we'll want to investigate what we are and aren't SILGen-ing
for textual interfaces of resilient modules, but for fragile modules
we may as well generate everything we can for potential optimization
purposes.

Author: jrose-apple

lib/SILGen/SILGen.cpp

@@ -904,7 +904,7 @@ void SILGenModule::emitObjCAllocatorDestructor(ClassDecl *cd,
                                                DestructorDecl *dd) {
   // Emit the native deallocating destructor for -dealloc.
   // Destructors are a necessary part of class metadata, so can't be delayed.
-  {
+  if (dd->hasBody()) {
     SILDeclRef dealloc(dd, SILDeclRef::Kind::Deallocator);
     SILFunction *f = getFunction(dealloc, ForDefinition);
     preEmitFunction(dealloc, dd, f, dd);
@@ -916,7 +916,7 @@ void SILGenModule::emitObjCAllocatorDestructor(ClassDecl *cd,
 
   // Emit the Objective-C -dealloc entry point if it has
   // something to do beyond messaging the superclass's -dealloc.
-  if (dd->getBody()->getNumElements() != 0)
+  if (dd->hasBody() && dd->getBody()->getNumElements() != 0)
     emitObjCDestructorThunk(dd);
 
   // Emit the ivar initializer, if needed.

test/ModuleInterface/ObjC.swiftinterface

@@ -0,0 +1,59 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module -o %t/ObjC.swiftmodule -O -enable-objc-interop %s
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -emit-module -o %t/ObjC.swiftmodule -O -enable-objc-interop -enable-resilience %s
+
+// FIXME: This test is self-contained, so it shouldn't require objc_interop
+// (just -enable-objc-interop), but it's failing in Linux SILGen.
+// https://bugs.swift.org/browse/SR-8877
+// REQUIRES: objc_interop
+
+import Foundation
+
+public class SomeClass {
+  @objc init?(_: Any)
+  @objc func foo()
+  @objc var bar: Int { get set }
+  @objc subscript(_: Int) -> Int { get set }
+  @objc deinit
+}
+
+public class SomeClassInlinable {
+  @usableFromInline init()
+  @objc @inlinable convenience init?(_: Any) { self.init() }
+  @objc @inlinable func foo() {}
+  @objc var bar: Int {
+    @inlinable get { return 0 }
+    @inlinable set {}
+  }
+  @objc @inlinable subscript(_: Int) -> Int {
+    @inlinable get { return 0 }
+    @inlinable set {}
+  }
+  @objc @inlinable deinit {
+    print("bye")
+  }
+}
+public class SomeNSObject : NSObject {
+  @objc init?(_: Any)
+  @objc func foo()
+  @objc var bar: Int { get set }
+  @objc subscript(_: Int) -> Int { get set }
+  @objc deinit
+}
+
+public class SomeNSObjectInlinable : NSObject {
+  public override init()
+  @objc @inlinable convenience init?(_: Any) { self.init() }
+  @objc @inlinable func foo() {}
+  @objc var bar: Int {
+    @inlinable get { return 0 }
+    @inlinable set {}
+  }
+  @objc @inlinable subscript(_: Int) -> Int {
+    @inlinable get { return 0 }
+    @inlinable set {}
+  }
+  @objc @inlinable deinit {
+    print("bye")
+  }
+}