[LLDB] Add ObjC object typeref support to SwiftRuntimeTypeVisitor

This is done by defering to the Objective-C runtime. This
functionality is implemented in the visitor because ObjC object
typerefs are fully valid reference types in the Swift reflection
descriptors already and only LLDB wants to look inside them.

rdar://154450536

Author: adrian-prantl

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntimeDynamicTypeResolution.cpp

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "LLDBMemoryReader.h"
+#include "Plugins/LanguageRuntime/ObjC/AppleObjCRuntime/AppleObjCRuntime.h"
 #include "Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.h"
 #include "ReflectionContextInterface.h"
 #include "SwiftLanguageRuntime.h"
@@ -800,9 +801,7 @@ class SwiftRuntimeTypeVisitor {
 
 llvm::Expected<unsigned>
 SwiftRuntimeTypeVisitor::VisitImpl(std::optional<unsigned> visit_only,
-                                   VisitCallback visit_callback)
-
-{
+                                   VisitCallback visit_callback) {
   if (!m_type)
     return llvm::createStringError("invalid type");
 
@@ -1113,6 +1112,77 @@ SwiftRuntimeTypeVisitor::VisitImpl(std::optional<unsigned> visit_only,
       if (ts.IsBuiltinType(m_type))
         return 0;
 
+      // Resolve ObjC references via the ObjC runtime.
+      auto visit_objcclass = [&](const swift::reflection::ObjCClassTypeRef &tr)
+          -> llvm::Expected<unsigned> {
+        auto process = m_exe_ctx.GetProcessPtr();
+        if (!process)
+          return llvm::createStringError(
+              "cannot resolve objc type without process");
+        auto objc_runtime = SwiftLanguageRuntime::GetObjCRuntime(*process);
+        if (!process)
+          return llvm::createStringError("no Objective-C runtime");
+        const std::string &name = tr.getName();
+        AppleObjCRuntime::ObjCISA isa = objc_runtime->GetISA(ConstString(name));
+        if (!isa)
+          return llvm::createStringError("no Objective-C class " + name);
+        AppleObjCRuntime::ClassDescriptorSP desc_sp =
+            objc_runtime->GetClassDescriptorFromISA(isa);
+        if (!desc_sp)
+          return llvm::createStringError("no class descriptor for " + name);
+        unsigned n = desc_sp->GetNumIVars();
+        if (count_only) {
+          if (!m_hide_superclass && desc_sp->GetSuperclass())
+            return n + 1;
+          return n;
+        }
+        unsigned depth = 0;
+        if (!m_hide_superclass)
+          if (AppleObjCRuntime::ClassDescriptorSP superclass_desc_sp =
+                  desc_sp->GetSuperclass()) {
+            auto get_name = [&]() -> std::string {
+              return superclass_desc_sp->GetClassName().GetString();
+            };
+            auto get_info = [&]() -> llvm::Expected<ChildInfo> {
+              return ChildInfo();
+            };
+            CompilerType type;
+            if (TypeSP type_sp = superclass_desc_sp->GetType())
+              type = type_sp->GetForwardCompilerType();
+            if (auto err = visit_callback(type, depth, get_name, get_info))
+              return err;
+            if (visit_only)
+              return success;
+          }
+
+        for (unsigned i = 0; i < n; ++i) {
+          auto ivar = desc_sp->GetIVarAtIndex(i);
+          if (!visit_only || *visit_only == i) {
+            auto get_name = [&]() -> std::string {
+              return ivar.m_name.GetString();
+            };
+            auto get_info = [&]() -> llvm::Expected<ChildInfo> {
+              ChildInfo child;
+              child.byte_size = ivar.m_size;
+              child.byte_offset = ivar.m_offset;
+              child.bitfield_bit_size = 0;
+              child.bitfield_bit_offset = 0;
+              child.is_base_class = false;
+              child.is_deref_of_parent = false;
+              child.language_flags = 0;
+              return child;
+            };
+            if (auto err =
+                    visit_callback(ivar.m_type, depth, get_name, get_info))
+              return err;
+          }
+        }
+        return success;
+      };
+      if (auto *obj_tr =
+              llvm::dyn_cast_or_null<swift::reflection::ObjCClassTypeRef>(tr))
+        return visit_objcclass(*obj_tr);
+
       LLDBTypeInfoProvider tip(m_runtime, ts);
       auto cti_or_err = reflection_ctx->GetClassInstanceTypeInfo(
           *tr, &tip, ts.GetDescriptorFinder());

lldb/test/API/lang/swift/objc_obj_field/Header.h

@@ -0,0 +1,10 @@
+
+#include <Foundation/Foundation.h>
+
+@protocol ObjcProtocol <NSObject>
+@end
+
+@interface ObjcClass : NSObject <ObjcProtocol>
+@property NSString *someString;
+- (instancetype)init;
+@end

lldb/test/API/lang/swift/objc_obj_field/Makefile

@@ -0,0 +1,6 @@
+SWIFT_SOURCES := main.swift
+SWIFT_BRIDGING_HEADER := Header.h
+OBJC_SOURCES := objc.m
+SWIFT_OBJC_INTEROP := 1
+
+include Makefile.rules

lldb/test/API/lang/swift/objc_obj_field/TestSwiftObjCObjField.py

@@ -0,0 +1,25 @@
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbutil as lldbutil
+
+
+class TestCase(TestBase):
+
+    @swiftTest
+    @skipUnlessDarwin
+    def test(self):
+        self.build()
+        target, process, thread, bkpt = lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.swift")
+        )
+        frame = thread.frames[0]
+        self.expect('settings set symbols.swift-enable-ast-context false')
+        c = frame.FindVariable("c")
+        self.assertEqual(c.GetNumChildren(), 1)
+        obj = c.GetChildAtIndex(0)
+        self.assertEqual(obj.GetNumChildren(), 2)
+        base = obj.GetChildAtIndex(0)
+        self.assertEqual(base.GetName(), "ObjectiveC.NSObject")
+        string = obj.GetChildAtIndex(1)
+        self.assertEqual(string.GetSummary(), '"The objc string"')

lldb/test/API/lang/swift/objc_obj_field/main.swift

@@ -0,0 +1,10 @@
+class C {
+    let objcClass = ObjcClass()!
+}
+
+func f(_ c: C) {
+  print("break here")
+}
+
+f(C())
+

lldb/test/API/lang/swift/objc_obj_field/objc.m

@@ -0,0 +1,13 @@
+#include "Header.h"
+
+@implementation ObjcClass
+
+- (instancetype)init {
+  self = [super init];
+  if (self) {
+    self.someString = @"The objc string";
+  }
+  return self;
+}
+
+@end