[lldb] Remove assumption from Clang-based data formatters that their types are in the scratch AST

[teemperor]

Summary

Several data formatters assume their types are in the Target's scratch AST and build
new types from that scratch AST instance. However, types from different ASTs shouldn't be
mixed, so this (unchecked) assumption may lead to problems if we ever have more than
one scratch AST or someone somehow invokes data formatters on a type that are not in the scratch AST.

Instead we can use in all the formatters just the TypeSystem of the type we're formatting. That's much
simpler and avoids all the headache of finding the right TypeSystem that matches the one of the formatted
type.

Right now LLDB only has one scratch TypeSystemClang instance and we format only types that are
in the scratch AST, so this doesn't change anything in the current way LLDB works. The intention here
is to allow follow up refactorings that introduce multiple scratch ASTs with the same Target.

lldb/source/DataFormatters/VectorType.cpp

lldb::ValueObjectSP GetChildAtIndex(size_t idx) override {
     return child_sp;
   }
 
   bool Update() override {
     m_parent_format = m_backend.GetFormat();
     CompilerType parent_type(m_backend.GetCompilerType());
     CompilerType element_type;
     parent_type.IsVectorType(&element_type, nullptr);
-    TypeSystem *type_system = nullptr;
-    if (auto target_sp = m_backend.GetTargetSP()) {
-      auto type_system_or_err =
-          target_sp->GetScratchTypeSystemForLanguage(lldb::eLanguageTypeC);
-      if (auto err = type_system_or_err.takeError()) {
-        LLDB_LOG_ERROR(
-            lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DATAFORMATTERS),
-            std::move(err), "Unable to update from scratch TypeSystem");
-      } else {
-        type_system = &type_system_or_err.get();
-      }
-    }
-    m_child_type =
-        ::GetCompilerTypeForFormat(m_parent_format, element_type, type_system);
+    m_child_type = ::GetCompilerTypeForFormat(m_parent_format, element_type,
+                                              parent_type.GetTypeSystem());
     m_num_children = ::CalculateNumChildren(parent_type, m_child_type);
     m_item_format = GetItemFormatForFormat(m_parent_format, m_child_type);
     return false;
   }
 
   bool MightHaveChildren() override { return true; }
 
   size_t GetIndexOfChildWithName(ConstString name) override {

lldb/source/Plugins/Language/CPlusPlus/BlockPointer.cpp

BlockPointerSyntheticFrontEnd(lldb::ValueObjectSP valobj_sp)
     if (auto err = type_system_or_err.takeError()) {
       LLDB_LOG_ERROR(
           lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DATAFORMATTERS),
           std::move(err), "Failed to get scratch TypeSystemClang");
       return;
     }
 
     TypeSystemClang *clang_ast_context =
-        llvm::dyn_cast<TypeSystemClang>(&type_system_or_err.get());
-
-    if (!clang_ast_context) {
-      return;
-    }
+        llvm::cast<TypeSystemClang>(block_pointer_type.GetTypeSystem());
 
     std::shared_ptr<ClangASTImporter> clang_ast_importer;
     auto *state = target_sp->GetPersistentExpressionStateForLanguage(
         lldb::eLanguageTypeC_plus_plus);
     if (state) {
       auto *persistent_vars = llvm::cast<ClangPersistentVariables>(state);
       clang_ast_importer = persistent_vars->GetClangASTImporter();
     }

lldb/source/Plugins/Language/ObjC/CoreMedia.cpp

 using namespace lldb_private::formatters;
 
 bool lldb_private::formatters::CMTimeSummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
   CompilerType type = valobj.GetCompilerType();
   if (!type.IsValid())
     return false;
 
-  auto type_system_or_err =
-      valobj.GetExecutionContextRef()
-          .GetTargetSP()
-          ->GetScratchTypeSystemForLanguage(lldb::eLanguageTypeC);
-  if (auto err = type_system_or_err.takeError()) {
-    LLDB_LOG_ERROR(
-        lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DATAFORMATTERS),
-        std::move(err), "Failed to get scratch type system");
-    return false;
-  }
+  TypeSystem *type_system = type.GetTypeSystem();
   // fetch children by offset to compensate for potential lack of debug info
-  auto int64_ty = type_system_or_err->GetBuiltinTypeForEncodingAndBitSize(
-      eEncodingSint, 64);
-  auto int32_ty = type_system_or_err->GetBuiltinTypeForEncodingAndBitSize(
-      eEncodingSint, 32);
+  auto int64_ty =
+      type_system->GetBuiltinTypeForEncodingAndBitSize(eEncodingSint, 64);
+  auto int32_ty =
+      type_system->GetBuiltinTypeForEncodingAndBitSize(eEncodingSint, 32);
 
   auto value_sp(valobj.GetSyntheticChildAtOffset(0, int64_ty, true));
   auto timescale_sp(valobj.GetSyntheticChildAtOffset(8, int32_ty, true));
   auto flags_sp(valobj.GetSyntheticChildAtOffset(12, int32_ty, true));
 
   if (!value_sp || !timescale_sp || !flags_sp)
     return false;