[lldb] Wire-up TypeSystemSwiftTypeRef::GetNumChildren

lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.cpp

@@ -1508,10 +1508,9 @@ template <> bool Equivalent<ConstString>(ConstString l, ConstString r) {
   return l == r;
 }
 
-/// Version taylored to GetBitSize & friends.
-template <>
-bool Equivalent<llvm::Optional<uint64_t>>(llvm::Optional<uint64_t> l,
-                                          llvm::Optional<uint64_t> r) {
+/// Version tailored to GetBitSize & friends.
+template <typename T>
+bool Equivalent(llvm::Optional<T> l, llvm::Optional<T> r) {
   if (l == r)
     return true;
   // There are situations where SwiftASTContext incorrectly returns
@@ -1526,6 +1525,12 @@ bool Equivalent<llvm::Optional<uint64_t>>(llvm::Optional<uint64_t> l,
   return false;
 }
 
+// Introduced for `GetNumChildren`.
+template <typename T>
+bool Equivalent(llvm::Optional<T> l, T r) {
+  return Equivalent(l, llvm::Optional<T>(r));
+}
+
 } // namespace
 #endif
 
@@ -2066,13 +2071,34 @@ lldb::Encoding TypeSystemSwiftTypeRef::GetEncoding(opaque_compiler_type_t type,
 lldb::Format TypeSystemSwiftTypeRef::GetFormat(opaque_compiler_type_t type) {
   return m_swift_ast_context->GetFormat(ReconstructType(type));
 }
+
 uint32_t
 TypeSystemSwiftTypeRef::GetNumChildren(opaque_compiler_type_t type,
                                        bool omit_empty_base_classes,
                                        const ExecutionContext *exe_ctx) {
-  return m_swift_ast_context->GetNumChildren(ReconstructType(type),
-                                             omit_empty_base_classes, exe_ctx);
+  if (exe_ctx)
+    if (auto *exe_scope = exe_ctx->GetBestExecutionContextScope())
+      if (auto *runtime =
+              SwiftLanguageRuntime::Get(exe_scope->CalculateProcess()))
+        if (auto num_children =
+                runtime->GetNumChildren(GetCanonicalType(type), nullptr)) {
+          // Use a lambda to intercept and unwrap the `Optional` return value.
+          return [&]() {
+            auto impl = [&]() { return num_children; };
+            VALIDATE_AND_RETURN(
+                impl, GetNumChildren, type,
+                (ReconstructType(type), omit_empty_base_classes, exe_ctx));
+          }().getValue();
+        }
+
+  LLDB_LOGF(GetLogIfAllCategoriesSet(LIBLLDB_LOG_TYPES),
+            "Using SwiftASTContext::GetNumChildren fallback for type %s",
+            AsMangledName(type));
+
+  return m_swift_ast_context->GetNumChildren(
+        ReconstructType(type), omit_empty_base_classes, exe_ctx);
 }
+
 uint32_t TypeSystemSwiftTypeRef::GetNumFields(opaque_compiler_type_t type) {
   return m_swift_ast_context->GetNumFields(ReconstructType(type));
 }

lldb/source/Target/SwiftLanguageRuntimeDynamicTypeResolution.cpp

@@ -1010,8 +1010,23 @@ SwiftLanguageRuntimeImpl::GetNumChildren(CompilerType type,
   // Structs and Tuples.
   if (auto *rti =
           llvm::dyn_cast_or_null<swift::reflection::RecordTypeInfo>(ti)) {
-    auto fields = rti->getFields();
-    return fields.size();
+    switch (rti->getRecordKind()) {
+    case swift::reflection::RecordKind::ThickFunction:
+      // There are two fields, `function` and `context`, but they're not exposed
+      // by lldb.
+      return 0;
+    case swift::reflection::RecordKind::OpaqueExistential:
+      // `OpaqueExistential` is documented as:
+      //     An existential is a three-word buffer followed by value metadata...
+      // The buffer is exposed as children named `payload_data_{0,1,2}`, and
+      // the number of fields are increased to match.
+      return rti->getNumFields() + 3;
+    default:
+      return rti->getNumFields();
+    }
+  }
+  if (auto *eti = llvm::dyn_cast_or_null<swift::reflection::EnumTypeInfo>(ti)) {
+    return eti->getNumPayloadCases();
   }
   // FIXME: Implement more cases.
   return {};

lldb/test/API/lang/swift/implementation_only_imports/library_resilient/TestLibraryResilient.py

@@ -82,7 +82,7 @@ def cleanup():
         # This test is deliberately checking what the user will see, rather than
         # the structure provided by the Python API, in order to test the recovery.
         self.expect("fr var", substrs=[
-            "(SomeLibrary.ContainsTwoInts) container = (other = 10)",
+            "(SomeLibrary.ContainsTwoInts) container = {", "other = 10",
             "(Int) simple = 1"])
         self.expect("e container", substrs=["(SomeLibrary.ContainsTwoInts)", "other = 10"])
         self.expect("e container.wrapped", error=True, substrs=["value of type 'ContainsTwoInts' has no member 'wrapped'"])