vendor/llvm-project/llvmorg-10-init-17466-ge26a78e7085

28 files changed, 1108 insertions, 1639 deletions

diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.cpp
deleted file mode 100644
index f33a713cc0b22..0000000000000
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.cpp
+++ /dev/null
@@ -1,104 +0,0 @@
-//===-- ASTDumper.cpp -------------------------------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "ASTDumper.h"
-
-#include "lldb/Symbol/ClangASTContext.h"
-#include "lldb/Symbol/ClangUtil.h"
-#include "lldb/Symbol/CompilerType.h"
-#include "lldb/Utility/Log.h"
-
-#include "llvm/Support/raw_ostream.h"
-
-using namespace lldb_private;
-
-ASTDumper::ASTDumper(clang::Decl *decl) {
-  clang::DeclContext *decl_ctx = llvm::dyn_cast<clang::DeclContext>(decl);
-
-  bool has_external_lexical_storage;
-  bool has_external_visible_storage;
-
-  if (decl_ctx) {
-    has_external_lexical_storage = decl_ctx->hasExternalLexicalStorage();
-    has_external_visible_storage = decl_ctx->hasExternalVisibleStorage();
-    decl_ctx->setHasExternalLexicalStorage(false);
-    decl_ctx->setHasExternalVisibleStorage(false);
-  }
-
-  llvm::raw_string_ostream os(m_dump);
-  decl->print(os);
-  os.flush();
-
-  if (decl_ctx) {
-    decl_ctx->setHasExternalLexicalStorage(has_external_lexical_storage);
-    decl_ctx->setHasExternalVisibleStorage(has_external_visible_storage);
-  }
-}
-
-ASTDumper::ASTDumper(clang::DeclContext *decl_ctx) {
-  bool has_external_lexical_storage = decl_ctx->hasExternalLexicalStorage();
-  bool has_external_visible_storage = decl_ctx->hasExternalVisibleStorage();
-
-  decl_ctx->setHasExternalLexicalStorage(false);
-  decl_ctx->setHasExternalVisibleStorage(false);
-
-  if (clang::Decl *decl = llvm::dyn_cast<clang::Decl>(decl_ctx)) {
-    llvm::raw_string_ostream os(m_dump);
-    decl->print(os);
-    os.flush();
-  } else {
-    m_dump.assign("<DeclContext is not a Decl>");
-  }
-
-  decl_ctx->setHasExternalLexicalStorage(has_external_lexical_storage);
-  decl_ctx->setHasExternalVisibleStorage(has_external_visible_storage);
-}
-
-ASTDumper::ASTDumper(const clang::Type *type) {
-  m_dump = clang::QualType(type, 0).getAsString();
-}
-
-ASTDumper::ASTDumper(clang::QualType type) { m_dump = type.getAsString(); }
-
-ASTDumper::ASTDumper(lldb::opaque_compiler_type_t type) {
-  m_dump = clang::QualType::getFromOpaquePtr(type).getAsString();
-}
-
-ASTDumper::ASTDumper(const CompilerType &compiler_type) {
-  m_dump = ClangUtil::GetQualType(compiler_type).getAsString();
-}
-
-const char *ASTDumper::GetCString() { return m_dump.c_str(); }
-
-void ASTDumper::ToLog(Log *log, const char *prefix) {
-  size_t len = m_dump.length() + 1;
-
-  char *alloc = (char *)malloc(len);
-  char *str = alloc;
-
-  memcpy(str, m_dump.c_str(), len);
-
-  char *end = nullptr;
-
-  end = strchr(str, '\n');
-
-  while (end) {
-    *end = '\0';
-
-    LLDB_LOGF(log, "%s%s", prefix, str);
-
-    *end = '\n';
-
-    str = end + 1;
-    end = strchr(str, '\n');
-  }
-
-  LLDB_LOGF(log, "%s%s", prefix, str);
-
-  free(alloc);
-}
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.h b/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.h
deleted file mode 100644
index ddf055d9c0c3d..0000000000000
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTDumper.h
+++ /dev/null
@@ -1,40 +0,0 @@
-//===-- ASTDumper.h ---------------------------------------------*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef liblldb_ASTDumper_h_
-#define liblldb_ASTDumper_h_
-
-#include "clang/AST/DeclVisitor.h"
-#include "clang/AST/TypeVisitor.h"
-
-#include "lldb/Utility/Stream.h"
-#include "llvm/ADT/DenseSet.h"
-
-namespace lldb_private {
-
-class ASTDumper {
-public:
-  ASTDumper(clang::Decl *decl);
-  ASTDumper(clang::DeclContext *decl_ctx);
-  ASTDumper(const clang::Type *type);
-  ASTDumper(clang::QualType type);
-  ASTDumper(lldb::opaque_compiler_type_t type);
-  ASTDumper(const CompilerType &compiler_type);
-
-  const char *GetCString();
-  void ToSTDERR();
-  void ToLog(Log *log, const char *prefix);
-  void ToStream(lldb::StreamSP &stream);
-
-private:
-  std::string m_dump;
-};
-
-} // namespace lldb_private
-
-#endif
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp
index 68eaad33f51ce..77bb9544ea406 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp
@@ -388,8 +388,7 @@ bool ASTResultSynthesizer::SynthesizeBodyResult(CompoundStmt *Body,
   // replace the old statement with the new one
   //
 
-  *last_stmt_ptr =
-      reinterpret_cast<Stmt *>(result_initialization_stmt_result.get());
+  *last_stmt_ptr = static_cast<Stmt *>(result_initialization_stmt_result.get());
 
   return true;
 }
@@ -448,13 +447,20 @@ void ASTResultSynthesizer::RecordPersistentDecl(NamedDecl *D) {
 }
 
 void ASTResultSynthesizer::CommitPersistentDecls() {
+  auto *state =
+      m_target.GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC);
+  if (!state)
+    return;
+
+  auto *persistent_vars = llvm::cast<ClangPersistentVariables>(state);
+  ClangASTContext *scratch_ctx = ClangASTContext::GetScratch(m_target);
+
   for (clang::NamedDecl *decl : m_decls) {
     StringRef name = decl->getName();
     ConstString name_cs(name.str().c_str());
 
     Decl *D_scratch = m_target.GetClangASTImporter()->DeportDecl(
-        m_target.GetScratchClangASTContext()->getASTContext(), m_ast_context,
-        decl);
+        &scratch_ctx->getASTContext(), decl);
 
     if (!D_scratch) {
       Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
@@ -472,10 +478,8 @@ void ASTResultSynthesizer::CommitPersistentDecls() {
     }
 
     if (NamedDecl *NamedDecl_scratch = dyn_cast<NamedDecl>(D_scratch))
-      llvm::cast<ClangPersistentVariables>(
-          m_target.GetPersistentExpressionStateForLanguage(
-              lldb::eLanguageTypeC))
-          ->RegisterPersistentDecl(name_cs, NamedDecl_scratch);
+      persistent_vars->RegisterPersistentDecl(name_cs, NamedDecl_scratch,
+                                              scratch_ctx);
   }
 }
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.h b/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.h
index 670ba6dce72e1..0b0f3b97705d9 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.h
@@ -135,18 +135,11 @@ private:
   void RecordPersistentTypes(clang::DeclContext *FunDeclCtx);
 
   /// Given a TypeDecl, if it declares a type whose name starts with a dollar
-  /// sign, register it as a pointer type in the target's scratch
-  /// AST context.
-  ///
-  /// \param[in] Body
-  ///     The body of the function.
+  /// sign, register it as a pointer type in the target's scratch AST context.
   void MaybeRecordPersistentType(clang::TypeDecl *D);
 
   /// Given a NamedDecl, register it as a pointer type in the target's scratch
   /// AST context.
-  ///
-  /// \param[in] Body
-  ///     The body of the function.
   void RecordPersistentDecl(clang::NamedDecl *D);
 
   clang::ASTContext
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.cpp
index 190eacaa2b62b..a164d48ae3e05 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.cpp
@@ -30,8 +30,8 @@ ASTStructExtractor::ASTStructExtractor(ASTConsumer *passthrough,
                                        const char *struct_name,
                                        ClangFunctionCaller &function)
     : m_ast_context(nullptr), m_passthrough(passthrough),
-      m_passthrough_sema(nullptr), m_sema(nullptr), m_action(nullptr),
-      m_function(function), m_struct_name(struct_name) {
+      m_passthrough_sema(nullptr), m_sema(nullptr), m_function(function),
+      m_struct_name(struct_name) {
   if (!m_passthrough)
     return;
 
@@ -170,7 +170,6 @@ void ASTStructExtractor::PrintStats() {
 
 void ASTStructExtractor::InitializeSema(Sema &S) {
   m_sema = &S;
-  m_action = reinterpret_cast<Action *>(m_sema);
 
   if (m_passthrough_sema)
     m_passthrough_sema->InitializeSema(S);
@@ -178,7 +177,6 @@ void ASTStructExtractor::InitializeSema(Sema &S) {
 
 void ASTStructExtractor::ForgetSema() {
   m_sema = nullptr;
-  m_action = nullptr;
 
   if (m_passthrough_sema)
     m_passthrough_sema->ForgetSema();
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.h b/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.h
index 7aef2e254e1f6..078cf095975f9 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ASTStructExtractor.h
@@ -121,8 +121,6 @@ private:
                                            ///for passthrough.  NULL if it's an
                                            ///ASTConsumer.
   clang::Sema *m_sema;                     ///< The Sema to use.
-  clang::Action
-      *m_action; ///< The Sema to use, cast to an Action so it's usable.
 
   ClangFunctionCaller &m_function; ///< The function to populate with
                                    ///information about the argument structure.
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
index 372c2439ebf0a..42927ab6cc8a1 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp
@@ -8,7 +8,6 @@
 
 #include "ClangASTSource.h"
 
-#include "ASTDumper.h"
 #include "ClangDeclVendor.h"
 #include "ClangModulesDeclVendor.h"
 
@@ -50,114 +49,42 @@ private:
 };
 }
 
-ClangASTSource::ClangASTSource(const lldb::TargetSP &target)
+ClangASTSource::ClangASTSource(const lldb::TargetSP &target,
+                               const lldb::ClangASTImporterSP &importer)
     : m_import_in_progress(false), m_lookups_enabled(false), m_target(target),
       m_ast_context(nullptr), m_active_lexical_decls(), m_active_lookups() {
-  if (!target->GetUseModernTypeLookup()) {
-    m_ast_importer_sp = m_target->GetClangASTImporter();
-  }
+  m_ast_importer_sp = importer;
 }
 
-void ClangASTSource::InstallASTContext(clang::ASTContext &ast_context,
-                                       clang::FileManager &file_manager,
-                                       bool is_shared_context) {
-  m_ast_context = &ast_context;
-  m_file_manager = &file_manager;
-  if (m_target->GetUseModernTypeLookup()) {
-    // Configure the ExternalASTMerger.  The merger needs to be able to import
-    // types from any source that we would do lookups in, which includes the
-    // persistent AST context as well as the modules and Objective-C runtime
-    // AST contexts.
-
-    lldbassert(!m_merger_up);
-    clang::ExternalASTMerger::ImporterTarget target = {ast_context,
-                                                       file_manager};
-    std::vector<clang::ExternalASTMerger::ImporterSource> sources;
-    for (lldb::ModuleSP module_sp : m_target->GetImages().Modules()) {
-      auto type_system_or_err =
-          module_sp->GetTypeSystemForLanguage(lldb::eLanguageTypeC);
-      if (auto err = type_system_or_err.takeError()) {
-        LLDB_LOG_ERROR(
-            lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_EXPRESSIONS),
-            std::move(err), "Failed to get ClangASTContext");
-      } else if (auto *module_ast_ctx = llvm::cast_or_null<ClangASTContext>(
-                     &type_system_or_err.get())) {
-        lldbassert(module_ast_ctx->getASTContext());
-        lldbassert(module_ast_ctx->getFileManager());
-        sources.emplace_back(*module_ast_ctx->getASTContext(),
-                             *module_ast_ctx->getFileManager(),
-                             module_ast_ctx->GetOriginMap());
-      }
-    }
-
-    do {
-      lldb::ProcessSP process(m_target->GetProcessSP());
-
-      if (!process)
-        break;
-
-      ObjCLanguageRuntime *language_runtime(ObjCLanguageRuntime::Get(*process));
-
-      if (!language_runtime)
-        break;
-
-      if (auto *runtime_decl_vendor = llvm::dyn_cast_or_null<ClangDeclVendor>(
-              language_runtime->GetDeclVendor())) {
-        sources.push_back(runtime_decl_vendor->GetImporterSource());
-      }
-    } while (false);
-
-    do {
-      auto *modules_decl_vendor = m_target->GetClangModulesDeclVendor();
-
-      if (!modules_decl_vendor)
-        break;
-
-      sources.push_back(modules_decl_vendor->GetImporterSource());
-    } while (false);
-
-    if (!is_shared_context) {
-      // Update the scratch AST context's merger to reflect any new sources we
-      // might have come across since the last time an expression was parsed.
-
-      auto scratch_ast_context = static_cast<ClangASTContextForExpressions*>(
-          m_target->GetScratchClangASTContext());
-
-      scratch_ast_context->GetMergerUnchecked().AddSources(sources);
-
-      sources.push_back({*scratch_ast_context->getASTContext(),
-                         *scratch_ast_context->getFileManager(),
-                         scratch_ast_context->GetOriginMap()});
-    }
-
-    m_merger_up =
-        std::make_unique<clang::ExternalASTMerger>(target, sources);
-  } else {
-    m_ast_importer_sp->InstallMapCompleter(&ast_context, *this);
-  }
+void ClangASTSource::InstallASTContext(ClangASTContext &clang_ast_context) {
+  m_ast_context = &clang_ast_context.getASTContext();
+  m_clang_ast_context = &clang_ast_context;
+  m_file_manager = &m_ast_context->getSourceManager().getFileManager();
+  m_ast_importer_sp->InstallMapCompleter(m_ast_context, *this);
 }
 
 ClangASTSource::~ClangASTSource() {
-  if (m_ast_importer_sp)
-    m_ast_importer_sp->ForgetDestination(m_ast_context);
+  if (!m_ast_importer_sp)
+    return;
+
+  m_ast_importer_sp->ForgetDestination(m_ast_context);
 
+  if (!m_target)
+    return;
   // We are in the process of destruction, don't create clang ast context on
   // demand by passing false to
   // Target::GetScratchClangASTContext(create_on_demand).
   ClangASTContext *scratch_clang_ast_context =
-      m_target->GetScratchClangASTContext(false);
+      ClangASTContext::GetScratch(*m_target, false);
 
   if (!scratch_clang_ast_context)
     return;
 
-  clang::ASTContext *scratch_ast_context =
+  clang::ASTContext &scratch_ast_context =
       scratch_clang_ast_context->getASTContext();
 
-  if (!scratch_ast_context)
-    return;
-
-  if (m_ast_context != scratch_ast_context && m_ast_importer_sp)
-    m_ast_importer_sp->ForgetSource(scratch_ast_context, m_ast_context);
+  if (m_ast_context != &scratch_ast_context && m_ast_importer_sp)
+    m_ast_importer_sp->ForgetSource(&scratch_ast_context, m_ast_context);
 }
 
 void ClangASTSource::StartTranslationUnit(ASTConsumer *Consumer) {
@@ -279,9 +206,8 @@ void ClangASTSource::CompleteType(TagDecl *tag_decl) {
               current_id, static_cast<void *>(m_ast_context),
               static_cast<void *>(tag_decl), tag_decl->getName().str().c_str());
 
-    LLDB_LOGF(log, "      CTD[%u] Before:", current_id);
-    ASTDumper dumper((Decl *)tag_decl);
-    dumper.ToLog(log, "      [CTD] ");
+    LLDB_LOG(log, "      CTD[%u] Before:\n{0}", current_id,
+             ClangUtil::DumpDecl(tag_decl));
   }
 
   auto iter = m_active_lexical_decls.find(tag_decl);
@@ -291,9 +217,6 @@ void ClangASTSource::CompleteType(TagDecl *tag_decl) {
   ScopedLexicalDeclEraser eraser(m_active_lexical_decls, tag_decl);
 
   if (!m_ast_importer_sp) {
-    if (HasMerger()) {
-      GetMergerUnchecked().CompleteType(tag_decl);
-    }
     return;
   }
 
@@ -365,7 +288,6 @@ void ClangASTSource::CompleteType(TagDecl *tag_decl) {
       TypeList types;
 
       ConstString name(tag_decl->getName().str().c_str());
-      CompilerDeclContext namespace_decl;
 
       const ModuleList &module_list = m_target->GetImages();
 
@@ -407,50 +329,30 @@ void ClangASTSource::CompleteType(TagDecl *tag_decl) {
     }
   }
 
-  if (log) {
-    LLDB_LOGF(log, "      [CTD] After:");
-    ASTDumper dumper((Decl *)tag_decl);
-    dumper.ToLog(log, "      [CTD] ");
-  }
+  LLDB_LOG(log, "      [CTD] After:\n{0}", ClangUtil::DumpDecl(tag_decl));
 }
 
 void ClangASTSource::CompleteType(clang::ObjCInterfaceDecl *interface_decl) {
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-  if (log) {
-    LLDB_LOGF(log,
-              "    [CompleteObjCInterfaceDecl] on (ASTContext*)%p Completing "
-              "an ObjCInterfaceDecl named %s",
-              static_cast<void *>(m_ast_context),
-              interface_decl->getName().str().c_str());
-    LLDB_LOGF(log, "      [COID] Before:");
-    ASTDumper dumper((Decl *)interface_decl);
-    dumper.ToLog(log, "      [COID] ");
-  }
+  LLDB_LOGF(log,
+            "    [CompleteObjCInterfaceDecl] on (ASTContext*)%p Completing "
+            "an ObjCInterfaceDecl named %s",
+            static_cast<void *>(m_ast_context),
+            interface_decl->getName().str().c_str());
+  LLDB_LOG(log, "      [COID] Before:\n{0}",
+           ClangUtil::DumpDecl(interface_decl));
 
   if (!m_ast_importer_sp) {
-    if (HasMerger()) {
-      ObjCInterfaceDecl *complete_iface_decl =
-        GetCompleteObjCInterface(interface_decl);
-
-      if (complete_iface_decl && (complete_iface_decl != interface_decl)) {
-        m_merger_up->ForceRecordOrigin(interface_decl, {complete_iface_decl, &complete_iface_decl->getASTContext()});
-      }
-
-      GetMergerUnchecked().CompleteType(interface_decl);
-    } else {
-      lldbassert(0 && "No mechanism for completing a type!");
-    }
+    lldbassert(0 && "No mechanism for completing a type!");
     return;
   }
 
-  Decl *original_decl = nullptr;
-  ASTContext *original_ctx = nullptr;
+  ClangASTImporter::DeclOrigin original = m_ast_importer_sp->GetDeclOrigin(interface_decl);
 
-  if (m_ast_importer_sp->ResolveDeclOrigin(interface_decl, &original_decl,
-                                           &original_ctx)) {
+  if (original.Valid()) {
     if (ObjCInterfaceDecl *original_iface_decl =
-            dyn_cast<ObjCInterfaceDecl>(original_decl)) {
+            dyn_cast<ObjCInterfaceDecl>(original.decl)) {
       ObjCInterfaceDecl *complete_iface_decl =
           GetCompleteObjCInterface(original_iface_decl);
 
@@ -468,8 +370,7 @@ void ClangASTSource::CompleteType(clang::ObjCInterfaceDecl *interface_decl) {
 
   if (log) {
     LLDB_LOGF(log, "      [COID] After:");
-    ASTDumper dumper((Decl *)interface_decl);
-    dumper.ToLog(log, "      [COID] ");
+    LLDB_LOG(log, "      [COID] {0}", ClangUtil::DumpDecl(interface_decl));
   }
 }
 
@@ -519,23 +420,9 @@ void ClangASTSource::FindExternalLexicalDecls(
     llvm::function_ref<bool(Decl::Kind)> predicate,
     llvm::SmallVectorImpl<Decl *> &decls) {
 
-  if (HasMerger()) {
-    if (auto *interface_decl = dyn_cast<ObjCInterfaceDecl>(decl_context)) {
-      ObjCInterfaceDecl *complete_iface_decl =
-         GetCompleteObjCInterface(interface_decl);
-
-      if (complete_iface_decl && (complete_iface_decl != interface_decl)) {
-        m_merger_up->ForceRecordOrigin(interface_decl, {complete_iface_decl, &complete_iface_decl->getASTContext()});
-      }
-    }
-    return GetMergerUnchecked().FindExternalLexicalDecls(decl_context,
-                                                         predicate,
-                                                         decls);
-  } else if (!m_ast_importer_sp)
+  if (!m_ast_importer_sp)
     return;
 
-  ClangASTMetrics::RegisterLexicalQuery();
-
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
   const Decl *context_decl = dyn_cast<Decl>(decl_context);
@@ -574,42 +461,38 @@ void ClangASTSource::FindExternalLexicalDecls(
           current_id, static_cast<const void *>(m_ast_context));
   }
 
-  Decl *original_decl = nullptr;
-  ASTContext *original_ctx = nullptr;
+  ClangASTImporter::DeclOrigin original = m_ast_importer_sp->GetDeclOrigin(context_decl);
 
-  if (!m_ast_importer_sp->ResolveDeclOrigin(context_decl, &original_decl,
-                                            &original_ctx))
+  if (!original.Valid())
     return;
 
-  if (log) {
-    LLDB_LOGF(
-        log, "  FELD[%u] Original decl (ASTContext*)%p (Decl*)%p:", current_id,
-        static_cast<void *>(original_ctx), static_cast<void *>(original_decl));
-    ASTDumper(original_decl).ToLog(log, "    ");
-  }
+  LLDB_LOG(
+      log, "  FELD[{0}] Original decl (ASTContext*){1:x} (Decl*){2:x}:\n{3}",
+      current_id, static_cast<void *>(original.ctx),
+      static_cast<void *>(original.decl), ClangUtil::DumpDecl(original.decl));
 
   if (ObjCInterfaceDecl *original_iface_decl =
-          dyn_cast<ObjCInterfaceDecl>(original_decl)) {
+          dyn_cast<ObjCInterfaceDecl>(original.decl)) {
     ObjCInterfaceDecl *complete_iface_decl =
         GetCompleteObjCInterface(original_iface_decl);
 
     if (complete_iface_decl && (complete_iface_decl != original_iface_decl)) {
-      original_decl = complete_iface_decl;
-      original_ctx = &complete_iface_decl->getASTContext();
+      original.decl = complete_iface_decl;
+      original.ctx = &complete_iface_decl->getASTContext();
 
       m_ast_importer_sp->SetDeclOrigin(context_decl, complete_iface_decl);
     }
   }
 
-  if (TagDecl *original_tag_decl = dyn_cast<TagDecl>(original_decl)) {
-    ExternalASTSource *external_source = original_ctx->getExternalSource();
+  if (TagDecl *original_tag_decl = dyn_cast<TagDecl>(original.decl)) {
+    ExternalASTSource *external_source = original.ctx->getExternalSource();
 
     if (external_source)
       external_source->CompleteType(original_tag_decl);
   }
 
   const DeclContext *original_decl_context =
-      dyn_cast<DeclContext>(original_decl);
+      dyn_cast<DeclContext>(original.decl);
 
   if (!original_decl_context)
     return;
@@ -625,16 +508,16 @@ void ClangASTSource::FindExternalLexicalDecls(
     // See clang::ExternalASTSource::FindExternalLexicalDecls()
     if (predicate(decl->getKind())) {
       if (log) {
-        ASTDumper ast_dumper(decl);
+        std::string ast_dump = ClangUtil::DumpDecl(decl);
         if (const NamedDecl *context_named_decl =
                 dyn_cast<NamedDecl>(context_decl))
           LLDB_LOGF(log, "  FELD[%d] Adding [to %sDecl %s] lexical %sDecl %s",
                     current_id, context_named_decl->getDeclKindName(),
                     context_named_decl->getNameAsString().c_str(),
-                    decl->getDeclKindName(), ast_dumper.GetCString());
+                    decl->getDeclKindName(), ast_dump.c_str());
         else
           LLDB_LOGF(log, "  FELD[%d] Adding lexical %sDecl %s", current_id,
-                    decl->getDeclKindName(), ast_dumper.GetCString());
+                    decl->getDeclKindName(), ast_dump.c_str());
       }
 
       Decl *copied_decl = CopyDecl(decl);
@@ -647,20 +530,6 @@ void ClangASTSource::FindExternalLexicalDecls(
 
         m_ast_importer_sp->RequireCompleteType(copied_field_type);
       }
-      auto decl_context_non_const = const_cast<DeclContext *>(decl_context);
-
-      // The decl ended up in the wrong DeclContext. Let's fix that so
-      // the decl we copied will actually be found.
-      // FIXME: This is a horrible hack that shouldn't be necessary. However
-      // it seems our current setup sometimes fails to copy decls to the right
-      // place. See rdar://55129537.
-      if (copied_decl->getDeclContext() != decl_context) {
-        assert(copied_decl->getDeclContext()->containsDecl(copied_decl));
-        copied_decl->getDeclContext()->removeDecl(copied_decl);
-        copied_decl->setDeclContext(decl_context_non_const);
-        assert(!decl_context_non_const->containsDecl(copied_decl));
-        decl_context_non_const->addDeclInternal(copied_decl);
-      }
     } else {
       SkippedDecls = true;
     }
@@ -683,8 +552,6 @@ void ClangASTSource::FindExternalLexicalDecls(
 void ClangASTSource::FindExternalVisibleDecls(NameSearchContext &context) {
   assert(m_ast_context);
 
-  ClangASTMetrics::RegisterVisibleQuery();
-
   const ConstString name(context.m_decl_name.getAsString().c_str());
 
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
@@ -715,25 +582,6 @@ void ClangASTSource::FindExternalVisibleDecls(NameSearchContext &context) {
                 name.GetCString(), context.m_decl_context->getDeclKindName());
   }
 
-  if (HasMerger() && !isa<TranslationUnitDecl>(context.m_decl_context)
-      /* possibly handle NamespaceDecls here? */) {
-    if (auto *interface_decl =
-    dyn_cast<ObjCInterfaceDecl>(context.m_decl_context)) {
-      ObjCInterfaceDecl *complete_iface_decl =
-      GetCompleteObjCInterface(interface_decl);
-
-      if (complete_iface_decl && (complete_iface_decl != interface_decl)) {
-        GetMergerUnchecked().ForceRecordOrigin(
-            interface_decl,
-            {complete_iface_decl, &complete_iface_decl->getASTContext()});
-      }
-    }
-
-    GetMergerUnchecked().FindExternalVisibleDeclsByName(context.m_decl_context,
-                                                context.m_decl_name);
-    return; // otherwise we may need to fall back
-  }
-
   context.m_namespace_map = std::make_shared<ClangASTImporter::NamespaceMap>();
 
   if (const NamespaceDecl *namespace_context =
@@ -758,7 +606,7 @@ void ClangASTSource::FindExternalVisibleDecls(NameSearchContext &context) {
 
       FindExternalVisibleDecls(context, i->first, i->second, current_id);
     }
-  } else if (isa<ObjCInterfaceDecl>(context.m_decl_context) && !HasMerger()) {
+  } else if (isa<ObjCInterfaceDecl>(context.m_decl_context)) {
     FindObjCPropertyAndIvarDecls(context);
   } else if (!isa<TranslationUnitDecl>(context.m_decl_context)) {
     // we shouldn't be getting FindExternalVisibleDecls calls for these
@@ -788,7 +636,7 @@ void ClangASTSource::FindExternalVisibleDecls(NameSearchContext &context) {
 }
 
 clang::Sema *ClangASTSource::getSema() {
-  return ClangASTContext::GetASTContext(m_ast_context)->getSema();
+  return m_clang_ast_context->getSema();
 }
 
 bool ClangASTSource::IgnoreName(const ConstString name,
@@ -821,6 +669,9 @@ void ClangASTSource::FindExternalVisibleDecls(
   if (IgnoreName(name, true))
     return;
 
+  if (!m_target)
+    return;
+
   if (module_sp && namespace_decl) {
     CompilerDeclContext found_namespace_decl;
 
@@ -837,7 +688,7 @@ void ClangASTSource::FindExternalVisibleDecls(
                   module_sp->GetFileSpec().GetFilename().GetCString());
       }
     }
-  } else if (!HasMerger()) {
+  } else {
     const ModuleList &target_images = m_target->GetImages();
     std::lock_guard<std::recursive_mutex> guard(target_images.GetMutex());
 
@@ -1049,11 +900,10 @@ public:
 
 template <class D>
 DeclFromUser<D> DeclFromParser<D>::GetOrigin(ClangASTSource &source) {
-  DeclFromUser<> origin_decl;
-  source.ResolveDeclOrigin(this->decl, &origin_decl.decl, nullptr);
-  if (origin_decl.IsInvalid())
+  ClangASTImporter::DeclOrigin origin = source.GetDeclOrigin(this->decl);
+  if (!origin.Valid())
     return DeclFromUser<D>();
-  return DeclFromUser<D>(dyn_cast<D>(origin_decl.decl));
+  return DeclFromUser<D>(dyn_cast<D>(origin.decl));
 }
 
 template <class D>
@@ -1137,11 +987,8 @@ bool ClangASTSource::FindObjCMethodDeclsWithOrigin(
 
     Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-    if (log) {
-      ASTDumper dumper((Decl *)copied_method_decl);
-      LLDB_LOGF(log, "  CAS::FOMD[%d] found (%s) %s", current_id, log_info,
-                dumper.GetCString());
-    }
+    LLDB_LOG(log, "  CAS::FOMD[{0}] found ({1}) {2}", current_id, log_info,
+             ClangUtil::DumpDecl(copied_method_decl));
 
     context.AddNamedDecl(copied_method_decl);
   }
@@ -1152,21 +999,6 @@ bool ClangASTSource::FindObjCMethodDeclsWithOrigin(
 void ClangASTSource::FindObjCMethodDecls(NameSearchContext &context) {
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-  if (HasMerger()) {
-    if (auto *interface_decl = dyn_cast<ObjCInterfaceDecl>(context.m_decl_context)) {
-      ObjCInterfaceDecl *complete_iface_decl =
-          GetCompleteObjCInterface(interface_decl);
-
-      if (complete_iface_decl && (complete_iface_decl != context.m_decl_context)) {
-        m_merger_up->ForceRecordOrigin(interface_decl, {complete_iface_decl, &complete_iface_decl->getASTContext()});
-      }
-    }
-
-    GetMergerUnchecked().FindExternalVisibleDeclsByName(context.m_decl_context,
-                                                        context.m_decl_name);
-    return;
-  }
-
   static unsigned int invocation_id = 0;
   unsigned int current_id = invocation_id++;
 
@@ -1180,17 +1012,13 @@ void ClangASTSource::FindObjCMethodDecls(NameSearchContext &context) {
     return;
 
   do {
-    Decl *original_decl = nullptr;
-    ASTContext *original_ctx = nullptr;
-
-    m_ast_importer_sp->ResolveDeclOrigin(interface_decl, &original_decl,
-                                         &original_ctx);
+    ClangASTImporter::DeclOrigin original = m_ast_importer_sp->GetDeclOrigin(interface_decl);
 
-    if (!original_decl)
+    if (!original.Valid())
       break;
 
     ObjCInterfaceDecl *original_interface_decl =
-        dyn_cast<ObjCInterfaceDecl>(original_decl);
+        dyn_cast<ObjCInterfaceDecl>(original.decl);
 
     if (FindObjCMethodDeclsWithOrigin(current_id, context,
                                       original_interface_decl, "at origin"))
@@ -1343,11 +1171,8 @@ void ClangASTSource::FindObjCMethodDecls(NameSearchContext &context) {
         if (!copied_method_decl)
           continue;
 
-        if (log) {
-          ASTDumper dumper((Decl *)copied_method_decl);
-          LLDB_LOGF(log, "  CAS::FOMD[%d] found (in symbols) %s", current_id,
-                    dumper.GetCString());
-        }
+        LLDB_LOG(log, "  CAS::FOMD[{0}] found (in symbols)\n{1}", current_id,
+                 ClangUtil::DumpDecl(copied_method_decl));
 
         context.AddNamedDecl(copied_method_decl);
       }
@@ -1476,11 +1301,8 @@ static bool FindObjCPropertyAndIvarDeclsWithOrigin(
     DeclFromParser<ObjCPropertyDecl> parser_property_decl(
         origin_property_decl.Import(source));
     if (parser_property_decl.IsValid()) {
-      if (log) {
-        ASTDumper dumper((Decl *)parser_property_decl.decl);
-        LLDB_LOGF(log, "  CAS::FOPD[%d] found %s", current_id,
-                  dumper.GetCString());
-      }
+      LLDB_LOG(log, "  CAS::FOPD[{0}] found\n{1}", current_id,
+               ClangUtil::DumpDecl(parser_property_decl.decl));
 
       context.AddNamedDecl(parser_property_decl.decl);
       found = true;
@@ -1495,9 +1317,8 @@ static bool FindObjCPropertyAndIvarDeclsWithOrigin(
         origin_ivar_decl.Import(source));
     if (parser_ivar_decl.IsValid()) {
       if (log) {
-        ASTDumper dumper((Decl *)parser_ivar_decl.decl);
-        LLDB_LOGF(log, "  CAS::FOPD[%d] found %s", current_id,
-                  dumper.GetCString());
+        LLDB_LOG(log, "  CAS::FOPD[{0}] found\n{1}", current_id,
+                 ClangUtil::DumpDecl(parser_ivar_decl.decl));
       }
 
       context.AddNamedDecl(parser_ivar_decl.decl);
@@ -1736,8 +1557,6 @@ bool ClangASTSource::layoutRecordType(const RecordDecl *record, uint64_t &size,
                                       FieldOffsetMap &field_offsets,
                                       BaseOffsetMap &base_offsets,
                                       BaseOffsetMap &virtual_base_offsets) {
-  ClangASTMetrics::RegisterRecordLayout();
-
   static unsigned int invocation_id = 0;
   unsigned int current_id = invocation_id++;
 
@@ -1984,90 +1803,37 @@ NamespaceDecl *ClangASTSource::AddNamespace(
   return dyn_cast<NamespaceDecl>(copied_decl);
 }
 
-clang::QualType ClangASTSource::CopyTypeWithMerger(
-    clang::ASTContext &from_context,
-    clang::ExternalASTMerger &merger,
-    clang::QualType type) {
-  if (!merger.HasImporterForOrigin(from_context)) {
-    lldbassert(0 && "Couldn't find the importer for a source context!");
-    return QualType();
-  }
-
-  if (llvm::Expected<QualType> type_or_error =
-          merger.ImporterForOrigin(from_context).Import(type)) {
-    return *type_or_error;
-  } else {
-    Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS);
-    LLDB_LOG_ERROR(log, type_or_error.takeError(), "Couldn't import type: {0}");
-    return QualType();
-  }
-}
-
 clang::Decl *ClangASTSource::CopyDecl(Decl *src_decl) {
-  clang::ASTContext &from_context = src_decl->getASTContext();
   if (m_ast_importer_sp) {
-    return m_ast_importer_sp->CopyDecl(m_ast_context, &from_context, src_decl);
-  } else if (m_merger_up) {
-    if (!m_merger_up->HasImporterForOrigin(from_context)) {
-      lldbassert(0 && "Couldn't find the importer for a source context!");
-      return nullptr;
-    }
-
-    if (llvm::Expected<Decl *> decl_or_error =
-            m_merger_up->ImporterForOrigin(from_context).Import(src_decl)) {
-      return *decl_or_error;
-    } else {
-      Log *log =
-          lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS);
-      LLDB_LOG_ERROR(log, decl_or_error.takeError(),
-                     "Couldn't import decl: {0}");
-      return nullptr;
-    }
+    return m_ast_importer_sp->CopyDecl(m_ast_context, src_decl);
   } else {
     lldbassert(0 && "No mechanism for copying a decl!");
     return nullptr;
   }
 }
 
-bool ClangASTSource::ResolveDeclOrigin(const clang::Decl *decl,
-                                       clang::Decl **original_decl,
-                                       clang::ASTContext **original_ctx) {
+ClangASTImporter::DeclOrigin ClangASTSource::GetDeclOrigin(const clang::Decl *decl) {
   if (m_ast_importer_sp) {
-    return m_ast_importer_sp->ResolveDeclOrigin(decl, original_decl,
-                                                original_ctx);
-  } else if (m_merger_up) {
-    return false; // Implement this correctly in ExternalASTMerger
+    return m_ast_importer_sp->GetDeclOrigin(decl);
   } else {
     // this can happen early enough that no ExternalASTSource is installed.
-    return false;
+    return ClangASTImporter::DeclOrigin();
   }
 }
 
-clang::ExternalASTMerger &ClangASTSource::GetMergerUnchecked() {
-  lldbassert(m_merger_up != nullptr);
-  return *m_merger_up;
-}
-
 CompilerType ClangASTSource::GuardedCopyType(const CompilerType &src_type) {
   ClangASTContext *src_ast =
       llvm::dyn_cast_or_null<ClangASTContext>(src_type.GetTypeSystem());
   if (src_ast == nullptr)
     return CompilerType();
 
-  ClangASTMetrics::RegisterLLDBImport();
-
   SetImportInProgress(true);
 
   QualType copied_qual_type;
 
   if (m_ast_importer_sp) {
-    copied_qual_type =
-        m_ast_importer_sp->CopyType(m_ast_context, src_ast->getASTContext(),
-                                    ClangUtil::GetQualType(src_type));
-  } else if (m_merger_up) {
-    copied_qual_type =
-        CopyTypeWithMerger(*src_ast->getASTContext(), *m_merger_up,
-                 ClangUtil::GetQualType(src_type));
+    copied_qual_type = ClangUtil::GetQualType(
+        m_ast_importer_sp->CopyType(*m_clang_ast_context, src_type));
   } else {
     lldbassert(0 && "No mechanism for copying a type!");
     return CompilerType();
@@ -2081,8 +1847,7 @@ CompilerType ClangASTSource::GuardedCopyType(const CompilerType &src_type) {
     // seems to be generating bad types on occasion.
     return CompilerType();
 
-  return CompilerType(ClangASTContext::GetASTContext(m_ast_context),
-                      copied_qual_type.getAsOpaquePtr());
+  return m_clang_ast_context->GetType(copied_qual_type);
 }
 
 clang::NamedDecl *NameSearchContext::AddVarDecl(const CompilerType &type) {
@@ -2098,10 +1863,10 @@ clang::NamedDecl *NameSearchContext::AddVarDecl(const CompilerType &type) {
 
   IdentifierInfo *ii = m_decl_name.getAsIdentifierInfo();
 
-  clang::ASTContext *ast = lldb_ast->getASTContext();
+  clang::ASTContext &ast = lldb_ast->getASTContext();
 
   clang::NamedDecl *Decl = VarDecl::Create(
-      *ast, const_cast<DeclContext *>(m_decl_context), SourceLocation(),
+      ast, const_cast<DeclContext *>(m_decl_context), SourceLocation(),
       SourceLocation(), ii, ClangUtil::GetQualType(type), nullptr, SC_Static);
   m_decls.push_back(Decl);
 
@@ -2127,7 +1892,7 @@ clang::NamedDecl *NameSearchContext::AddFunDecl(const CompilerType &type,
 
   QualType qual_type(ClangUtil::GetQualType(type));
 
-  clang::ASTContext *ast = lldb_ast->getASTContext();
+  clang::ASTContext &ast = lldb_ast->getASTContext();
 
   const bool isInlineSpecified = false;
   const bool hasWrittenPrototype = true;
@@ -2137,7 +1902,7 @@ clang::NamedDecl *NameSearchContext::AddFunDecl(const CompilerType &type,
 
   if (extern_c) {
     context = LinkageSpecDecl::Create(
-        *ast, context, SourceLocation(), SourceLocation(),
+        ast, context, SourceLocation(), SourceLocation(),
         clang::LinkageSpecDecl::LanguageIDs::lang_c, false);
   }
 
@@ -2149,7 +1914,7 @@ clang::NamedDecl *NameSearchContext::AddFunDecl(const CompilerType &type,
           : m_decl_name;
 
   clang::FunctionDecl *func_decl = FunctionDecl::Create(
-      *ast, context, SourceLocation(), SourceLocation(), decl_name, qual_type,
+      ast, context, SourceLocation(), SourceLocation(), decl_name, qual_type,
       nullptr, SC_Extern, isInlineSpecified, hasWrittenPrototype,
       isConstexprSpecified ? CSK_constexpr : CSK_unspecified);
 
@@ -2170,7 +1935,7 @@ clang::NamedDecl *NameSearchContext::AddFunDecl(const CompilerType &type,
       QualType arg_qual_type(func_proto_type->getParamType(ArgIndex));
 
       parm_var_decls.push_back(
-          ParmVarDecl::Create(*ast, const_cast<DeclContext *>(context),
+          ParmVarDecl::Create(ast, const_cast<DeclContext *>(context),
                               SourceLocation(), SourceLocation(), nullptr,
                               arg_qual_type, nullptr, SC_Static, nullptr));
     }
@@ -2210,9 +1975,7 @@ clang::NamedDecl *NameSearchContext::AddGenericFunDecl() {
       proto_info));
 
   return AddFunDecl(
-      CompilerType(ClangASTContext::GetASTContext(m_ast_source.m_ast_context),
-                   generic_function_type.getAsOpaquePtr()),
-      true);
+      m_ast_source.m_clang_ast_context->GetType(generic_function_type), true);
 }
 
 clang::NamedDecl *
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
index 7a8bacf48a8fd..3149b4266b2fd 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.h
@@ -12,10 +12,9 @@
 #include <set>
 
 #include "lldb/Symbol/ClangASTImporter.h"
-#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
 #include "lldb/Symbol/CompilerType.h"
 #include "lldb/Target/Target.h"
-#include "clang/AST/ExternalASTMerger.h"
+#include "clang/AST/ExternalASTSource.h"
 #include "clang/Basic/IdentifierTable.h"
 
 #include "llvm/ADT/SmallSet.h"
@@ -30,7 +29,7 @@ namespace lldb_private {
 /// knows the name it is looking for, but nothing else. The ExternalSemaSource
 /// class provides Decls (VarDecl, FunDecl, TypeDecl) to Clang for these
 /// names, consulting the ClangExpressionDeclMap to do the actual lookups.
-class ClangASTSource : public ClangExternalASTSourceCommon,
+class ClangASTSource : public clang::ExternalASTSource,
                        public ClangASTImporter::MapCompleter {
 public:
   /// Constructor
@@ -39,7 +38,11 @@ public:
   ///
   /// \param[in] target
   ///     A reference to the target containing debug information to use.
-  ClangASTSource(const lldb::TargetSP &target);
+  ///
+  /// \param[in] importer
+  ///     The ClangASTImporter to use.
+  ClangASTSource(const lldb::TargetSP &target,
+                 const lldb::ClangASTImporterSP &importer);
 
   /// Destructor
   ~ClangASTSource() override;
@@ -57,9 +60,7 @@ public:
   }
   void MaterializeVisibleDecls(const clang::DeclContext *DC) { return; }
 
-  void InstallASTContext(clang::ASTContext &ast_context,
-                         clang::FileManager &file_manager,
-                         bool is_shared_context = false);
+  void InstallASTContext(ClangASTContext &ast_context);
 
   //
   // APIs for ExternalASTSource
@@ -89,7 +90,7 @@ public:
   /// \param[in] DC
   ///     The DeclContext being searched.
   ///
-  /// \param[in] isKindWeWant
+  /// \param[in] IsKindWeWant
   ///     A callback function that returns true given the
   ///     DeclKinds of desired Decls, and false otherwise.
   ///
@@ -155,7 +156,7 @@ public:
   /// setHasExternalVisibleStorage() and setHasExternalLexicalStorage() that
   /// this object has something to say about undefined names.
   ///
-  /// \param[in] ASTConsumer
+  /// \param[in] Consumer
   ///     Unused.
   void StartTranslationUnit(clang::ASTConsumer *Consumer) override;
 
@@ -210,7 +211,7 @@ public:
   ///
   /// Clang AST contexts like to own their AST sources, so this is a state-
   /// free proxy object.
-  class ClangASTSourceProxy : public ClangExternalASTSourceCommon {
+  class ClangASTSourceProxy : public clang::ExternalASTSource {
   public:
     ClangASTSourceProxy(ClangASTSource &original) : m_original(original) {}
 
@@ -249,18 +250,6 @@ public:
       return m_original.StartTranslationUnit(Consumer);
     }
 
-    ClangASTMetadata *GetMetadata(const void *object) {
-      return m_original.GetMetadata(object);
-    }
-
-    void SetMetadata(const void *object, ClangASTMetadata &metadata) {
-      return m_original.SetMetadata(object, metadata);
-    }
-
-    bool HasMetadata(const void *object) {
-      return m_original.HasMetadata(object);
-    }
-
   private:
     ClangASTSource &m_original;
   };
@@ -321,13 +310,6 @@ protected:
   /// A wrapper for ClangASTContext::CopyType that sets a flag that
   /// indicates that we should not respond to queries during import.
   ///
-  /// \param[in] dest_context
-  ///     The target AST context, typically the parser's AST context.
-  ///
-  /// \param[in] source_context
-  ///     The source AST context, typically the AST context of whatever
-  ///     symbol file the type was found in.
-  ///
   /// \param[in] src_type
   ///     The source type.
   ///
@@ -341,7 +323,7 @@ public:
   /// \param[in] name
   ///     The name to be considered.
   ///
-  /// \param[in] ignore_all_dollar_nmmes
+  /// \param[in] ignore_all_dollar_names
   ///     True if $-names of all sorts should be ignored.
   ///
   /// \return
@@ -358,24 +340,6 @@ public:
   /// \return
   ///     A copy of the Decl in m_ast_context, or NULL if the copy failed.
   clang::Decl *CopyDecl(clang::Decl *src_decl);
-                         
-  /// Copies a single Type to the target of the given ExternalASTMerger.
-  ///
-  /// \param[in] src_context
-  ///     The ASTContext containing the type.
-  ///
-  /// \param[in] merger
-  ///     The merger to use.  This isn't just *m_merger_up because it might be
-  ///     the persistent AST context's merger.
-  ///
-  /// \param[in] type
-  ///     The type to copy.
-  ///
-  /// \return
-  ///     A copy of the Type in the merger's target context.
-	clang::QualType CopyTypeWithMerger(clang::ASTContext &src_context,
-                                     clang::ExternalASTMerger &merger,
-                                     clang::QualType type);
 
   /// Determined the origin of a single Decl, if it can be found.
   ///
@@ -390,16 +354,7 @@ public:
   ///
   /// \return
   ///     True if lookup succeeded; false otherwise.
-  bool ResolveDeclOrigin(const clang::Decl *decl, clang::Decl **original_decl,
-                         clang::ASTContext **original_ctx);
- 
-  /// Returns m_merger_up.  Only call this if the target is configured to use
-  /// modern lookup,
-	clang::ExternalASTMerger &GetMergerUnchecked();
- 
-  /// Returns true if there is a merger.  This only occurs if the target is
-  /// using modern lookup.
-  bool HasMerger() { return (bool)m_merger_up; }
+  ClangASTImporter::DeclOrigin GetDeclOrigin(const clang::Decl *decl);
 
 protected:
   bool FindObjCMethodDeclsWithOrigin(
@@ -411,15 +366,16 @@ protected:
   bool m_import_in_progress;
   bool m_lookups_enabled;
 
-  const lldb::TargetSP
-      m_target; ///< The target to use in finding variables and types.
-  clang::ASTContext
-      *m_ast_context; ///< The AST context requests are coming in for.
-  clang::FileManager
-      *m_file_manager; ///< The file manager paired with the AST context.
-  lldb::ClangASTImporterSP m_ast_importer_sp; ///< The target's AST importer.
-  std::unique_ptr<clang::ExternalASTMerger> m_merger_up;
-      ///< The ExternalASTMerger for this parse.
+  /// The target to use in finding variables and types.
+  const lldb::TargetSP m_target;
+  /// The AST context requests are coming in for.
+  clang::ASTContext *m_ast_context;
+  /// The ClangASTContext for m_ast_context.
+  ClangASTContext *m_clang_ast_context;
+  /// The file manager paired with the AST context.
+  clang::FileManager *m_file_manager;
+  /// The target's AST importer.
+  lldb::ClangASTImporterSP m_ast_importer_sp;
   std::set<const clang::Decl *> m_active_lexical_decls;
   std::set<const char *> m_active_lookups;
 };
@@ -432,20 +388,20 @@ protected:
 /// what name is being searched for and provides helper functions to construct
 /// Decls given appropriate type information.
 struct NameSearchContext {
-  ClangASTSource &m_ast_source; ///< The AST source making the request
-  llvm::SmallVectorImpl<clang::NamedDecl *>
-      &m_decls; ///< The list of declarations already constructed
-  ClangASTImporter::NamespaceMapSP m_namespace_map; ///< The mapping of all
-                                                    ///namespaces found for this
-                                                    ///request back to their
-                                                    ///modules
-  const clang::DeclarationName &m_decl_name; ///< The name being looked for
-  const clang::DeclContext
-      *m_decl_context; ///< The DeclContext to put declarations into
-  llvm::SmallSet<CompilerType, 5> m_function_types; ///< All the types of
-                                                    ///functions that have been
-                                                    ///reported, so we don't
-                                                    ///report conflicts
+  /// The AST source making the request.
+  ClangASTSource &m_ast_source;
+  /// The list of declarations already constructed.
+  llvm::SmallVectorImpl<clang::NamedDecl *> &m_decls;
+  /// The mapping of all namespaces found for this request back to their
+  /// modules.
+  ClangASTImporter::NamespaceMapSP m_namespace_map;
+  /// The name being looked for.
+  const clang::DeclarationName &m_decl_name;
+  /// The DeclContext to put declarations into.
+  const clang::DeclContext *m_decl_context;
+  /// All the types of functions that have been reported, so we don't
+  /// report conflicts.
+  llvm::SmallSet<CompilerType, 5> m_function_types;
 
   struct {
     bool variable : 1;
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.cpp
index c59722b7b4f89..c87507a25855b 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.cpp
@@ -15,16 +15,16 @@ using namespace lldb_private;
 
 uint32_t ClangDeclVendor::FindDecls(ConstString name, bool append,
                                     uint32_t max_matches,
-                                    std::vector<CompilerDecl> &decls) {
+                                    std::vector<clang::NamedDecl *> &decls) {
   if (!append)
     decls.clear();
 
-  std::vector<clang::NamedDecl *> named_decls;
-  uint32_t ret = FindDecls(name, /*append*/ false, max_matches, named_decls);
-  for (auto *named_decl : named_decls) {
-    decls.push_back(CompilerDecl(
-        ClangASTContext::GetASTContext(&named_decl->getASTContext()),
-        named_decl));
+  std::vector<CompilerDecl> compiler_decls;
+  uint32_t ret = FindDecls(name, /*append*/ false, max_matches, compiler_decls);
+  for (CompilerDecl compiler_decl : compiler_decls) {
+    clang::Decl *d = static_cast<clang::Decl *>(compiler_decl.GetOpaqueDecl());
+    clang::NamedDecl *nd = llvm::cast<clang::NamedDecl>(d);
+    decls.push_back(nd);
   }
   return ret;
 }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
index 90b715f37cba2..0c888de08841d 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.h
@@ -12,8 +12,6 @@
 #include "lldb/Core/ClangForward.h"
 #include "lldb/Symbol/DeclVendor.h"
 
-#include "clang/AST/ExternalASTMerger.h"
-
 namespace lldb_private {
 
 // A clang specialized extension to DeclVendor.
@@ -23,19 +21,10 @@ public:
 
   virtual ~ClangDeclVendor() {}
 
-  /// Interface for ExternalASTMerger. Returns an ImporterSource allowing type
-  /// completion.
-  ///
-  /// \return
-  ///     An ImporterSource for this ClangDeclVendor.
-  virtual clang::ExternalASTMerger::ImporterSource GetImporterSource() = 0;
+  using DeclVendor::FindDecls;
 
   uint32_t FindDecls(ConstString name, bool append, uint32_t max_matches,
-                     std::vector<CompilerDecl> &decls) override;
-
-  virtual uint32_t FindDecls(ConstString name, bool append,
-                             uint32_t max_matches,
-                             std::vector<clang::NamedDecl *> &decls) = 0;
+                     std::vector<clang::NamedDecl *> &decls);
 
   static bool classof(const DeclVendor *vendor) {
     return vendor->GetKind() >= eClangDeclVendor &&
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
index f4457fc1b7404..bf3023be5f60d 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp
@@ -8,7 +8,6 @@
 
 #include "ClangExpressionDeclMap.h"
 
-#include "ASTDumper.h"
 #include "ClangASTSource.h"
 #include "ClangModulesDeclVendor.h"
 #include "ClangPersistentVariables.h"
@@ -20,6 +19,7 @@
 #include "lldb/Core/ValueObjectVariable.h"
 #include "lldb/Expression/Materializer.h"
 #include "lldb/Symbol/ClangASTContext.h"
+#include "lldb/Symbol/ClangUtil.h"
 #include "lldb/Symbol/CompileUnit.h"
 #include "lldb/Symbol/CompilerDecl.h"
 #include "lldb/Symbol/CompilerDeclContext.h"
@@ -65,9 +65,10 @@ const char *g_lldb_local_vars_namespace_cstr = "$__lldb_local_vars";
 ClangExpressionDeclMap::ClangExpressionDeclMap(
     bool keep_result_in_memory,
     Materializer::PersistentVariableDelegate *result_delegate,
-    ExecutionContext &exe_ctx, ValueObject *ctx_obj)
-    : ClangASTSource(exe_ctx.GetTargetSP()), m_found_entities(),
-      m_struct_members(), m_keep_result_in_memory(keep_result_in_memory),
+    const lldb::TargetSP &target, const lldb::ClangASTImporterSP &importer,
+    ValueObject *ctx_obj)
+    : ClangASTSource(target, importer), m_found_entities(), m_struct_members(),
+      m_keep_result_in_memory(keep_result_in_memory),
       m_result_delegate(result_delegate), m_ctx_obj(ctx_obj), m_parser_vars(),
       m_struct_vars() {
   EnableStructVars();
@@ -84,8 +85,6 @@ ClangExpressionDeclMap::~ClangExpressionDeclMap() {
 
 bool ClangExpressionDeclMap::WillParse(ExecutionContext &exe_ctx,
                                        Materializer *materializer) {
-  ClangASTMetrics::ClearLocalCounters();
-
   EnableParserVars();
   m_parser_vars->m_exe_ctx = exe_ctx;
 
@@ -110,7 +109,7 @@ bool ClangExpressionDeclMap::WillParse(ExecutionContext &exe_ctx,
     m_parser_vars->m_persistent_vars = llvm::cast<ClangPersistentVariables>(
         target->GetPersistentExpressionStateForLanguage(eLanguageTypeC));
 
-    if (!target->GetScratchClangASTContext())
+    if (!ClangASTContext::GetScratch(*target))
       return false;
   }
 
@@ -127,12 +126,7 @@ void ClangExpressionDeclMap::InstallCodeGenerator(
 }
 
 void ClangExpressionDeclMap::DidParse() {
-  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
-
-  if (log)
-    ClangASTMetrics::DumpCounters(log);
-
-  if (m_parser_vars) {
+  if (m_parser_vars && m_parser_vars->m_persistent_vars) {
     for (size_t entity_index = 0, num_entities = m_found_entities.GetSize();
          entity_index < num_entities; ++entity_index) {
       ExpressionVariableSP var_sp(
@@ -180,55 +174,15 @@ ClangExpressionDeclMap::TargetInfo ClangExpressionDeclMap::GetTargetInfo() {
   return ret;
 }
 
-static clang::QualType ExportAllDeclaredTypes(
-    clang::ExternalASTMerger &parent_merger, clang::ExternalASTMerger &merger,
-    clang::ASTContext &source, clang::FileManager &source_file_manager,
-    const clang::ExternalASTMerger::OriginMap &source_origin_map,
-    clang::FileID file, clang::QualType root) {
-  // Mark the source as temporary to make sure all declarations from the
-  // AST are exported. Also add the parent_merger as the merger into the
-  // source AST so that the merger can track back any declarations from
-  // the persistent ASTs we used as sources.
-  clang::ExternalASTMerger::ImporterSource importer_source(
-      source, source_file_manager, source_origin_map, /*Temporary*/ true,
-      &parent_merger);
-  merger.AddSources(importer_source);
-  clang::ASTImporter &exporter = merger.ImporterForOrigin(source);
-  llvm::Expected<clang::QualType> ret_or_error = exporter.Import(root);
-  merger.RemoveSources(importer_source);
-  if (ret_or_error) {
-    return *ret_or_error;
-  } else {
-    Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS);
-    LLDB_LOG_ERROR(log, ret_or_error.takeError(), "Couldn't import type: {0}");
-    return clang::QualType();
-  }
-}
-
 TypeFromUser ClangExpressionDeclMap::DeportType(ClangASTContext &target,
                                                 ClangASTContext &source,
                                                 TypeFromParser parser_type) {
-  assert(&target == m_target->GetScratchClangASTContext());
+  assert(&target == ClangASTContext::GetScratch(*m_target));
   assert((TypeSystem *)&source == parser_type.GetTypeSystem());
-  assert(source.getASTContext() == m_ast_context);
+  assert(&source.getASTContext() == m_ast_context);
 
   if (m_ast_importer_sp) {
-    return TypeFromUser(m_ast_importer_sp->DeportType(
-                            target.getASTContext(), source.getASTContext(),
-                            parser_type.GetOpaqueQualType()),
-                        &target);
-  } else if (m_merger_up) {
-    clang::FileID source_file =
-        source.getASTContext()->getSourceManager().getFileID(
-            source.getASTContext()->getTranslationUnitDecl()->getLocation());
-    auto scratch_ast_context = static_cast<ClangASTContextForExpressions *>(
-        m_target->GetScratchClangASTContext());
-    clang::QualType exported_type = ExportAllDeclaredTypes(
-        *m_merger_up.get(), scratch_ast_context->GetMergerUnchecked(),
-        *source.getASTContext(), *source.getFileManager(),
-        m_merger_up->GetOrigins(), source_file,
-        clang::QualType::getFromOpaquePtr(parser_type.GetOpaqueQualType()));
-    return TypeFromUser(exported_type.getAsOpaquePtr(), &target);
+    return TypeFromUser(m_ast_importer_sp->DeportType(target, parser_type));
   } else {
     lldbassert(0 && "No mechanism for deporting a type!");
     return TypeFromUser();
@@ -255,8 +209,11 @@ bool ClangExpressionDeclMap::AddPersistentVariable(const NamedDecl *decl,
     if (target == nullptr)
       return false;
 
-    TypeFromUser user_type =
-        DeportType(*target->GetScratchClangASTContext(), *ast, parser_type);
+    auto *clang_ast_context = ClangASTContext::GetScratch(*target);
+    if (!clang_ast_context)
+      return false;
+
+    TypeFromUser user_type = DeportType(*clang_ast_context, *ast, parser_type);
 
     uint32_t offset = m_parser_vars->m_materializer->AddResultVariable(
         user_type, is_lvalue, m_keep_result_in_memory, m_result_delegate, err);
@@ -291,7 +248,9 @@ bool ClangExpressionDeclMap::AddPersistentVariable(const NamedDecl *decl,
   if (target == nullptr)
     return false;
 
-  ClangASTContext *context(target->GetScratchClangASTContext());
+  ClangASTContext *context = ClangASTContext::GetScratch(*target);
+  if (!context)
+    return false;
 
   TypeFromUser user_type = DeportType(*context, *ast, parser_type);
 
@@ -303,6 +262,9 @@ bool ClangExpressionDeclMap::AddPersistentVariable(const NamedDecl *decl,
   if (!m_parser_vars->m_target_info.IsValid())
     return false;
 
+  if (!m_parser_vars->m_persistent_vars)
+    return false;
+
   ClangExpressionVariable *var = llvm::cast<ClangExpressionVariable>(
       m_parser_vars->m_persistent_vars
           ->CreatePersistentVariable(
@@ -368,7 +330,7 @@ bool ClangExpressionDeclMap::AddValueToStruct(const NamedDecl *decl,
   ClangExpressionVariable *var(ClangExpressionVariable::FindVariableInList(
       m_found_entities, decl, GetParserID()));
 
-  if (!var) {
+  if (!var && m_parser_vars->m_persistent_vars) {
     var = ClangExpressionVariable::FindVariableInList(
         *m_parser_vars->m_persistent_vars, decl, GetParserID());
     is_persistent_variable = true;
@@ -638,7 +600,7 @@ addr_t ClangExpressionDeclMap::GetSymbolAddress(ConstString name,
 
 lldb::VariableSP ClangExpressionDeclMap::FindGlobalVariable(
     Target &target, ModuleSP &module, ConstString name,
-    CompilerDeclContext *namespace_decl, TypeFromUser *type) {
+    CompilerDeclContext *namespace_decl) {
   VariableList vars;
 
   if (module && namespace_decl)
@@ -646,21 +608,9 @@ lldb::VariableSP ClangExpressionDeclMap::FindGlobalVariable(
   else
     target.GetImages().FindGlobalVariables(name, -1, vars);
 
-  if (vars.GetSize()) {
-    if (type) {
-      for (size_t i = 0; i < vars.GetSize(); ++i) {
-        VariableSP var_sp = vars.GetVariableAtIndex(i);
-
-        if (ClangASTContext::AreTypesSame(
-                *type, var_sp->GetType()->GetFullCompilerType()))
-          return var_sp;
-      }
-    } else {
-      return vars.GetVariableAtIndex(0);
-    }
-  }
-
-  return VariableSP();
+  if (vars.GetSize() == 0)
+    return VariableSP();
+  return vars.GetVariableAtIndex(0);
 }
 
 ClangASTContext *ClangExpressionDeclMap::GetClangASTContext() {
@@ -687,8 +637,6 @@ void ClangExpressionDeclMap::FindExternalVisibleDecls(
     NameSearchContext &context) {
   assert(m_ast_context);
 
-  ClangASTMetrics::RegisterVisibleQuery();
-
   const ConstString name(context.m_decl_name.getAsString().c_str());
 
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
@@ -727,9 +675,9 @@ void ClangExpressionDeclMap::FindExternalVisibleDecls(
           dyn_cast<NamespaceDecl>(context.m_decl_context)) {
     if (namespace_context->getName().str() ==
         std::string(g_lldb_local_vars_namespace_cstr)) {
-      CompilerDeclContext compiler_decl_ctx(
-          GetClangASTContext(), const_cast<void *>(static_cast<const void *>(
-                                    context.m_decl_context)));
+      CompilerDeclContext compiler_decl_ctx =
+          m_clang_ast_context->CreateDeclContext(
+              const_cast<clang::DeclContext *>(context.m_decl_context));
       FindExternalVisibleDecls(context, lldb::ModuleSP(), compiler_decl_ctx,
                                current_id);
       return;
@@ -771,743 +719,760 @@ void ClangExpressionDeclMap::FindExternalVisibleDecls(
   ClangASTSource::FindExternalVisibleDecls(context);
 }
 
-void ClangExpressionDeclMap::FindExternalVisibleDecls(
-    NameSearchContext &context, lldb::ModuleSP module_sp,
-    CompilerDeclContext &namespace_decl, unsigned int current_id) {
-  assert(m_ast_context);
+void ClangExpressionDeclMap::MaybeRegisterFunctionBody(
+    FunctionDecl *copied_function_decl) {
+  if (copied_function_decl->getBody() && m_parser_vars->m_code_gen) {
+    clang::DeclGroupRef decl_group_ref(copied_function_decl);
+    m_parser_vars->m_code_gen->HandleTopLevelDecl(decl_group_ref);
+  }
+}
 
-  std::function<void(clang::FunctionDecl *)> MaybeRegisterFunctionBody =
-      [this](clang::FunctionDecl *copied_function_decl) {
-        if (copied_function_decl->getBody() && m_parser_vars->m_code_gen) {
-          DeclGroupRef decl_group_ref(copied_function_decl);
-          m_parser_vars->m_code_gen->HandleTopLevelDecl(decl_group_ref);
-        }
-      };
+clang::NamedDecl *ClangExpressionDeclMap::GetPersistentDecl(ConstString name) {
+  if (!m_parser_vars)
+    return nullptr;
+  Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
+  if (!target)
+    return nullptr;
+
+  ClangASTContext::GetScratch(*target);
+
+  if (!m_parser_vars->m_persistent_vars)
+    return nullptr;
+  return m_parser_vars->m_persistent_vars->GetPersistentDecl(name);
+}
 
+void ClangExpressionDeclMap::SearchPersistenDecls(NameSearchContext &context,
+                                                  const ConstString name,
+                                                  unsigned int current_id) {
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-  SymbolContextList sc_list;
+  NamedDecl *persistent_decl = GetPersistentDecl(name);
 
-  const ConstString name(context.m_decl_name.getAsString().c_str());
-  if (IgnoreName(name, false))
+  if (!persistent_decl)
     return;
 
-  // Only look for functions by name out in our symbols if the function doesn't
-  // start with our phony prefix of '$'
-  Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
+  Decl *parser_persistent_decl = CopyDecl(persistent_decl);
+
+  if (!parser_persistent_decl)
+    return;
+
+  NamedDecl *parser_named_decl = dyn_cast<NamedDecl>(parser_persistent_decl);
+
+  if (!parser_named_decl)
+    return;
+
+  if (clang::FunctionDecl *parser_function_decl =
+          llvm::dyn_cast<clang::FunctionDecl>(parser_named_decl)) {
+    MaybeRegisterFunctionBody(parser_function_decl);
+  }
+
+  LLDB_LOGF(log, "  CEDM::FEVD[%u] Found persistent decl %s", current_id,
+            name.GetCString());
+
+  context.AddNamedDecl(parser_named_decl);
+}
+
+void ClangExpressionDeclMap::LookUpLldbClass(NameSearchContext &context,
+                                             unsigned int current_id) {
+  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
+
   StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
   SymbolContext sym_ctx;
   if (frame != nullptr)
     sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
                                       lldb::eSymbolContextBlock);
 
-  // Try the persistent decls, which take precedence over all else.
-  if (!namespace_decl) {
-    do {
-      if (!target)
-        break;
+  if (m_ctx_obj) {
+    Status status;
+    lldb::ValueObjectSP ctx_obj_ptr = m_ctx_obj->AddressOf(status);
+    if (!ctx_obj_ptr || status.Fail())
+      return;
 
-      ClangASTContext *scratch_clang_ast_context =
-          target->GetScratchClangASTContext();
+    AddThisType(context, TypeFromUser(m_ctx_obj->GetCompilerType()),
+                current_id);
 
-      if (!scratch_clang_ast_context)
-        break;
+    m_struct_vars->m_object_pointer_type =
+        TypeFromUser(ctx_obj_ptr->GetCompilerType());
 
-      ASTContext *scratch_ast_context =
-          scratch_clang_ast_context->getASTContext();
+    return;
+  }
 
-      if (!scratch_ast_context)
-        break;
+  // Clang is looking for the type of "this"
 
-      NamedDecl *persistent_decl =
-          m_parser_vars->m_persistent_vars->GetPersistentDecl(name);
+  if (frame == nullptr)
+    return;
 
-      if (!persistent_decl)
-        break;
+  // Find the block that defines the function represented by "sym_ctx"
+  Block *function_block = sym_ctx.GetFunctionBlock();
 
-      Decl *parser_persistent_decl = CopyDecl(persistent_decl);
+  if (!function_block)
+    return;
 
-      if (!parser_persistent_decl)
-        break;
+  CompilerDeclContext function_decl_ctx = function_block->GetDeclContext();
 
-      NamedDecl *parser_named_decl =
-          dyn_cast<NamedDecl>(parser_persistent_decl);
+  if (!function_decl_ctx)
+    return;
 
-      if (!parser_named_decl)
-        break;
+  clang::CXXMethodDecl *method_decl =
+      ClangASTContext::DeclContextGetAsCXXMethodDecl(function_decl_ctx);
 
-      if (clang::FunctionDecl *parser_function_decl =
-              llvm::dyn_cast<clang::FunctionDecl>(parser_named_decl)) {
-        MaybeRegisterFunctionBody(parser_function_decl);
-      }
+  if (method_decl) {
+    clang::CXXRecordDecl *class_decl = method_decl->getParent();
 
-      LLDB_LOGF(log, "  CEDM::FEVD[%u] Found persistent decl %s", current_id,
-                name.GetCString());
+    QualType class_qual_type(class_decl->getTypeForDecl(), 0);
 
-      context.AddNamedDecl(parser_named_decl);
-    } while (false);
-  }
+    TypeFromUser class_user_type(class_qual_type.getAsOpaquePtr(),
+                                 function_decl_ctx.GetTypeSystem());
 
-  if (name.GetCString()[0] == '$' && !namespace_decl) {
-    static ConstString g_lldb_class_name("$__lldb_class");
+    LLDB_LOG(log, "  CEDM::FEVD[{0}] Adding type for $__lldb_class: {1}",
+             current_id, class_qual_type.getAsString());
 
-    if (name == g_lldb_class_name) {
-      if (m_ctx_obj) {
-        Status status;
-        lldb::ValueObjectSP ctx_obj_ptr = m_ctx_obj->AddressOf(status);
-        if (!ctx_obj_ptr || status.Fail())
-          return;
+    AddThisType(context, class_user_type, current_id);
 
-        AddThisType(context, TypeFromUser(m_ctx_obj->GetCompilerType()),
-                    current_id);
+    if (method_decl->isInstance()) {
+      // self is a pointer to the object
 
-        m_struct_vars->m_object_pointer_type =
-            TypeFromUser(ctx_obj_ptr->GetCompilerType());
+      QualType class_pointer_type =
+          method_decl->getASTContext().getPointerType(class_qual_type);
 
-        return;
-      }
+      TypeFromUser self_user_type(class_pointer_type.getAsOpaquePtr(),
+                                  function_decl_ctx.GetTypeSystem());
 
-      // Clang is looking for the type of "this"
+      m_struct_vars->m_object_pointer_type = self_user_type;
+    }
+    return;
+  }
 
-      if (frame == nullptr)
-        return;
+  // This branch will get hit if we are executing code in the context of
+  // a function that claims to have an object pointer (through
+  // DW_AT_object_pointer?) but is not formally a method of the class.
+  // In that case, just look up the "this" variable in the current scope
+  // and use its type.
+  // FIXME: This code is formally correct, but clang doesn't currently
+  // emit DW_AT_object_pointer
+  // for C++ so it hasn't actually been tested.
 
-      // Find the block that defines the function represented by "sym_ctx"
-      Block *function_block = sym_ctx.GetFunctionBlock();
+  VariableList *vars = frame->GetVariableList(false);
 
-      if (!function_block)
-        return;
+  lldb::VariableSP this_var = vars->FindVariable(ConstString("this"));
 
-      CompilerDeclContext function_decl_ctx = function_block->GetDeclContext();
+  if (this_var && this_var->IsInScope(frame) &&
+      this_var->LocationIsValidForFrame(frame)) {
+    Type *this_type = this_var->GetType();
 
-      if (!function_decl_ctx)
-        return;
+    if (!this_type)
+      return;
 
-      clang::CXXMethodDecl *method_decl =
-          ClangASTContext::DeclContextGetAsCXXMethodDecl(function_decl_ctx);
+    TypeFromUser pointee_type =
+        this_type->GetForwardCompilerType().GetPointeeType();
 
-      if (method_decl) {
-        clang::CXXRecordDecl *class_decl = method_decl->getParent();
+    LLDB_LOG(log, "  FEVD[{0}] Adding type for $__lldb_class: {1}", current_id,
+             ClangUtil::GetQualType(pointee_type).getAsString());
 
-        QualType class_qual_type(class_decl->getTypeForDecl(), 0);
+    AddThisType(context, pointee_type, current_id);
+    TypeFromUser this_user_type(this_type->GetFullCompilerType());
+    m_struct_vars->m_object_pointer_type = this_user_type;
+  }
+}
 
-        TypeFromUser class_user_type(
-            class_qual_type.getAsOpaquePtr(),
-            ClangASTContext::GetASTContext(&class_decl->getASTContext()));
+void ClangExpressionDeclMap::LookUpLldbObjCClass(NameSearchContext &context,
+                                                 unsigned int current_id) {
+  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-        if (log) {
-          ASTDumper ast_dumper(class_qual_type);
-          LLDB_LOGF(log, "  CEDM::FEVD[%u] Adding type for $__lldb_class: %s",
-                    current_id, ast_dumper.GetCString());
-        }
+  StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
 
-        AddThisType(context, class_user_type, current_id);
+  if (m_ctx_obj) {
+    Status status;
+    lldb::ValueObjectSP ctx_obj_ptr = m_ctx_obj->AddressOf(status);
+    if (!ctx_obj_ptr || status.Fail())
+      return;
 
-        if (method_decl->isInstance()) {
-          // self is a pointer to the object
+    AddOneType(context, TypeFromUser(m_ctx_obj->GetCompilerType()), current_id);
 
-          QualType class_pointer_type =
-              method_decl->getASTContext().getPointerType(class_qual_type);
+    m_struct_vars->m_object_pointer_type =
+        TypeFromUser(ctx_obj_ptr->GetCompilerType());
 
-          TypeFromUser self_user_type(
-              class_pointer_type.getAsOpaquePtr(),
-              ClangASTContext::GetASTContext(&method_decl->getASTContext()));
+    return;
+  }
 
-          m_struct_vars->m_object_pointer_type = self_user_type;
-        }
-      } else {
-        // This branch will get hit if we are executing code in the context of
-        // a function that claims to have an object pointer (through
-        // DW_AT_object_pointer?) but is not formally a method of the class.
-        // In that case, just look up the "this" variable in the current scope
-        // and use its type.
-        // FIXME: This code is formally correct, but clang doesn't currently
-        // emit DW_AT_object_pointer
-        // for C++ so it hasn't actually been tested.
+  // Clang is looking for the type of "*self"
+
+  if (!frame)
+    return;
 
-        VariableList *vars = frame->GetVariableList(false);
+  SymbolContext sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
+                                                  lldb::eSymbolContextBlock);
 
-        lldb::VariableSP this_var = vars->FindVariable(ConstString("this"));
+  // Find the block that defines the function represented by "sym_ctx"
+  Block *function_block = sym_ctx.GetFunctionBlock();
 
-        if (this_var && this_var->IsInScope(frame) &&
-            this_var->LocationIsValidForFrame(frame)) {
-          Type *this_type = this_var->GetType();
+  if (!function_block)
+    return;
 
-          if (!this_type)
-            return;
+  CompilerDeclContext function_decl_ctx = function_block->GetDeclContext();
 
-          TypeFromUser pointee_type =
-              this_type->GetForwardCompilerType().GetPointeeType();
+  if (!function_decl_ctx)
+    return;
 
-          if (pointee_type.IsValid()) {
-            if (log) {
-              ASTDumper ast_dumper(pointee_type);
-              LLDB_LOGF(log, "  FEVD[%u] Adding type for $__lldb_class: %s",
-                        current_id, ast_dumper.GetCString());
-            }
+  clang::ObjCMethodDecl *method_decl =
+      ClangASTContext::DeclContextGetAsObjCMethodDecl(function_decl_ctx);
 
-            AddThisType(context, pointee_type, current_id);
-            TypeFromUser this_user_type(this_type->GetFullCompilerType());
-            m_struct_vars->m_object_pointer_type = this_user_type;
-            return;
-          }
-        }
-      }
+  if (method_decl) {
+    ObjCInterfaceDecl *self_interface = method_decl->getClassInterface();
 
+    if (!self_interface)
       return;
-    }
 
-    static ConstString g_lldb_objc_class_name("$__lldb_objc_class");
-    if (name == g_lldb_objc_class_name) {
-      if (m_ctx_obj) {
-        Status status;
-        lldb::ValueObjectSP ctx_obj_ptr = m_ctx_obj->AddressOf(status);
-        if (!ctx_obj_ptr || status.Fail())
-          return;
+    const clang::Type *interface_type = self_interface->getTypeForDecl();
 
-        AddOneType(context, TypeFromUser(m_ctx_obj->GetCompilerType()),
-                   current_id);
+    if (!interface_type)
+      return; // This is unlikely, but we have seen crashes where this
+              // occurred
 
-        m_struct_vars->m_object_pointer_type =
-            TypeFromUser(ctx_obj_ptr->GetCompilerType());
+    TypeFromUser class_user_type(QualType(interface_type, 0).getAsOpaquePtr(),
+                                 function_decl_ctx.GetTypeSystem());
 
-        return;
-      }
+    LLDB_LOG(log, "  FEVD[{0}] Adding type for $__lldb_objc_class: {1}",
+             current_id, ClangUtil::ToString(interface_type));
 
-      // Clang is looking for the type of "*self"
+    AddOneType(context, class_user_type, current_id);
 
-      if (!frame)
-        return;
+    if (method_decl->isInstanceMethod()) {
+      // self is a pointer to the object
 
-      SymbolContext sym_ctx = frame->GetSymbolContext(
-          lldb::eSymbolContextFunction | lldb::eSymbolContextBlock);
+      QualType class_pointer_type =
+          method_decl->getASTContext().getObjCObjectPointerType(
+              QualType(interface_type, 0));
 
-      // Find the block that defines the function represented by "sym_ctx"
-      Block *function_block = sym_ctx.GetFunctionBlock();
+      TypeFromUser self_user_type(class_pointer_type.getAsOpaquePtr(),
+                                  function_decl_ctx.GetTypeSystem());
 
-      if (!function_block)
-        return;
+      m_struct_vars->m_object_pointer_type = self_user_type;
+    } else {
+      // self is a Class pointer
+      QualType class_type = method_decl->getASTContext().getObjCClassType();
 
-      CompilerDeclContext function_decl_ctx = function_block->GetDeclContext();
+      TypeFromUser self_user_type(class_type.getAsOpaquePtr(),
+                                  function_decl_ctx.GetTypeSystem());
 
-      if (!function_decl_ctx)
-        return;
+      m_struct_vars->m_object_pointer_type = self_user_type;
+    }
 
-      clang::ObjCMethodDecl *method_decl =
-          ClangASTContext::DeclContextGetAsObjCMethodDecl(function_decl_ctx);
+    return;
+  }
+  // This branch will get hit if we are executing code in the context of
+  // a function that claims to have an object pointer (through
+  // DW_AT_object_pointer?) but is not formally a method of the class.
+  // In that case, just look up the "self" variable in the current scope
+  // and use its type.
 
-      if (method_decl) {
-        ObjCInterfaceDecl *self_interface = method_decl->getClassInterface();
+  VariableList *vars = frame->GetVariableList(false);
 
-        if (!self_interface)
-          return;
+  lldb::VariableSP self_var = vars->FindVariable(ConstString("self"));
 
-        const clang::Type *interface_type = self_interface->getTypeForDecl();
+  if (!self_var)
+    return;
+  if (!self_var->IsInScope(frame))
+    return;
+  if (!self_var->LocationIsValidForFrame(frame))
+    return;
 
-        if (!interface_type)
-          return; // This is unlikely, but we have seen crashes where this
-                  // occurred
+  Type *self_type = self_var->GetType();
 
-        TypeFromUser class_user_type(
-            QualType(interface_type, 0).getAsOpaquePtr(),
-            ClangASTContext::GetASTContext(&method_decl->getASTContext()));
+  if (!self_type)
+    return;
 
-        if (log) {
-          ASTDumper ast_dumper(interface_type);
-          LLDB_LOGF(log, "  FEVD[%u] Adding type for $__lldb_objc_class: %s",
-                    current_id, ast_dumper.GetCString());
-        }
+  CompilerType self_clang_type = self_type->GetFullCompilerType();
 
-        AddOneType(context, class_user_type, current_id);
+  if (ClangASTContext::IsObjCClassType(self_clang_type)) {
+    return;
+  }
+  if (!ClangASTContext::IsObjCObjectPointerType(self_clang_type))
+    return;
+  self_clang_type = self_clang_type.GetPointeeType();
 
-        if (method_decl->isInstanceMethod()) {
-          // self is a pointer to the object
+  if (!self_clang_type)
+    return;
 
-          QualType class_pointer_type =
-              method_decl->getASTContext().getObjCObjectPointerType(
-                  QualType(interface_type, 0));
+  LLDB_LOG(log, "  FEVD[{0}] Adding type for $__lldb_objc_class: {1}",
+           current_id, ClangUtil::ToString(self_type->GetFullCompilerType()));
 
-          TypeFromUser self_user_type(
-              class_pointer_type.getAsOpaquePtr(),
-              ClangASTContext::GetASTContext(&method_decl->getASTContext()));
+  TypeFromUser class_user_type(self_clang_type);
 
-          m_struct_vars->m_object_pointer_type = self_user_type;
-        } else {
-          // self is a Class pointer
-          QualType class_type = method_decl->getASTContext().getObjCClassType();
+  AddOneType(context, class_user_type, current_id);
 
-          TypeFromUser self_user_type(
-              class_type.getAsOpaquePtr(),
-              ClangASTContext::GetASTContext(&method_decl->getASTContext()));
+  TypeFromUser self_user_type(self_type->GetFullCompilerType());
 
-          m_struct_vars->m_object_pointer_type = self_user_type;
-        }
+  m_struct_vars->m_object_pointer_type = self_user_type;
+}
 
-        return;
-      } else {
-        // This branch will get hit if we are executing code in the context of
-        // a function that claims to have an object pointer (through
-        // DW_AT_object_pointer?) but is not formally a method of the class.
-        // In that case, just look up the "self" variable in the current scope
-        // and use its type.
+void ClangExpressionDeclMap::LookupLocalVarNamespace(
+    SymbolContext &sym_ctx, NameSearchContext &name_context) {
+  if (sym_ctx.block == nullptr)
+    return;
 
-        VariableList *vars = frame->GetVariableList(false);
+  CompilerDeclContext frame_decl_context = sym_ctx.block->GetDeclContext();
+  if (!frame_decl_context)
+    return;
 
-        lldb::VariableSP self_var = vars->FindVariable(ConstString("self"));
+  ClangASTContext *frame_ast = llvm::dyn_cast_or_null<ClangASTContext>(
+      frame_decl_context.GetTypeSystem());
+  if (!frame_ast)
+    return;
 
-        if (self_var && self_var->IsInScope(frame) &&
-            self_var->LocationIsValidForFrame(frame)) {
-          Type *self_type = self_var->GetType();
+  clang::NamespaceDecl *namespace_decl =
+      m_clang_ast_context->GetUniqueNamespaceDeclaration(
+          g_lldb_local_vars_namespace_cstr, nullptr);
+  if (!namespace_decl)
+    return;
 
-          if (!self_type)
-            return;
+  name_context.AddNamedDecl(namespace_decl);
+  clang::DeclContext *ctxt = clang::Decl::castToDeclContext(namespace_decl);
+  ctxt->setHasExternalVisibleStorage(true);
+  name_context.m_found.local_vars_nsp = true;
+}
 
-          CompilerType self_clang_type = self_type->GetFullCompilerType();
+void ClangExpressionDeclMap::LookupInModulesDeclVendor(
+    NameSearchContext &context, ConstString name, unsigned current_id) {
+  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-          if (ClangASTContext::IsObjCClassType(self_clang_type)) {
-            return;
-          } else if (ClangASTContext::IsObjCObjectPointerType(
-                         self_clang_type)) {
-            self_clang_type = self_clang_type.GetPointeeType();
+  if (!m_target)
+    return;
 
-            if (!self_clang_type)
-              return;
+  auto *modules_decl_vendor = m_target->GetClangModulesDeclVendor();
+  if (!modules_decl_vendor)
+    return;
 
-            if (log) {
-              ASTDumper ast_dumper(self_type->GetFullCompilerType());
-              LLDB_LOGF(log,
-                        "  FEVD[%u] Adding type for $__lldb_objc_class: %s",
-                        current_id, ast_dumper.GetCString());
-            }
+  bool append = false;
+  uint32_t max_matches = 1;
+  std::vector<clang::NamedDecl *> decls;
 
-            TypeFromUser class_user_type(self_clang_type);
+  if (!modules_decl_vendor->FindDecls(name, append, max_matches, decls))
+    return;
 
-            AddOneType(context, class_user_type, current_id);
+  assert(!decls.empty() && "FindDecls returned true but no decls?");
+  clang::NamedDecl *const decl_from_modules = decls[0];
 
-            TypeFromUser self_user_type(self_type->GetFullCompilerType());
+  LLDB_LOG(log,
+           "  CAS::FEVD[{0}] Matching decl found for "
+           "\"{1}\" in the modules",
+           current_id, name);
 
-            m_struct_vars->m_object_pointer_type = self_user_type;
-            return;
-          }
-        }
-      }
+  clang::Decl *copied_decl = CopyDecl(decl_from_modules);
+  if (!copied_decl) {
+    LLDB_LOG(log,
+             "  CAS::FEVD[{0}] - Couldn't export a "
+             "declaration from the modules",
+             current_id);
+    return;
+  }
 
-      return;
-    }
+  if (auto copied_function = dyn_cast<clang::FunctionDecl>(copied_decl)) {
+    MaybeRegisterFunctionBody(copied_function);
 
-    if (name == ConstString(g_lldb_local_vars_namespace_cstr)) {
-      CompilerDeclContext frame_decl_context =
-          sym_ctx.block != nullptr ? sym_ctx.block->GetDeclContext()
-                                   : CompilerDeclContext();
-
-      if (frame_decl_context) {
-        ClangASTContext *ast = llvm::dyn_cast_or_null<ClangASTContext>(
-            frame_decl_context.GetTypeSystem());
-
-        if (ast) {
-          clang::NamespaceDecl *namespace_decl =
-              ClangASTContext::GetUniqueNamespaceDeclaration(
-                  m_ast_context, name.GetCString(), nullptr);
-          if (namespace_decl) {
-            context.AddNamedDecl(namespace_decl);
-            clang::DeclContext *clang_decl_ctx =
-                clang::Decl::castToDeclContext(namespace_decl);
-            clang_decl_ctx->setHasExternalVisibleStorage(true);
-            context.m_found.local_vars_nsp = true;
-          }
-        }
-      }
+    context.AddNamedDecl(copied_function);
 
-      return;
-    }
+    context.m_found.function_with_type_info = true;
+    context.m_found.function = true;
+  } else if (auto copied_var = dyn_cast<clang::VarDecl>(copied_decl)) {
+    context.AddNamedDecl(copied_var);
+    context.m_found.variable = true;
+  }
+}
 
-    // any other $__lldb names should be weeded out now
-    if (name.GetStringRef().startswith("$__lldb"))
-      return;
+bool ClangExpressionDeclMap::LookupLocalVariable(
+    NameSearchContext &context, ConstString name, unsigned current_id,
+    SymbolContext &sym_ctx, CompilerDeclContext &namespace_decl) {
+  if (sym_ctx.block == nullptr)
+    return false;
 
-    ExpressionVariableSP pvar_sp(
-        m_parser_vars->m_persistent_vars->GetVariable(name));
+  CompilerDeclContext decl_context = sym_ctx.block->GetDeclContext();
+  if (!decl_context)
+    return false;
 
-    if (pvar_sp) {
-      AddOneVariable(context, pvar_sp, current_id);
-      return;
+  // Make sure that the variables are parsed so that we have the
+  // declarations.
+  StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
+  VariableListSP vars = frame->GetInScopeVariableList(true);
+  for (size_t i = 0; i < vars->GetSize(); i++)
+    vars->GetVariableAtIndex(i)->GetDecl();
+
+  // Search for declarations matching the name. Do not include imported
+  // decls in the search if we are looking for decls in the artificial
+  // namespace $__lldb_local_vars.
+  std::vector<CompilerDecl> found_decls =
+      decl_context.FindDeclByName(name, namespace_decl.IsValid());
+
+  VariableSP var;
+  bool variable_found = false;
+  for (CompilerDecl decl : found_decls) {
+    for (size_t vi = 0, ve = vars->GetSize(); vi != ve; ++vi) {
+      VariableSP candidate_var = vars->GetVariableAtIndex(vi);
+      if (candidate_var->GetDecl() == decl) {
+        var = candidate_var;
+        break;
+      }
     }
 
-    const char *reg_name(&name.GetCString()[1]);
+    if (var && !variable_found) {
+      variable_found = true;
+      ValueObjectSP valobj = ValueObjectVariable::Create(frame, var);
+      AddOneVariable(context, var, valobj, current_id);
+      context.m_found.variable = true;
+    }
+  }
+  return variable_found;
+}
 
-    if (m_parser_vars->m_exe_ctx.GetRegisterContext()) {
-      const RegisterInfo *reg_info(
-          m_parser_vars->m_exe_ctx.GetRegisterContext()->GetRegisterInfoByName(
-              reg_name));
+/// Structure to hold the info needed when comparing function
+/// declarations.
+namespace {
+struct FuncDeclInfo {
+  ConstString m_name;
+  CompilerType m_copied_type;
+  uint32_t m_decl_lvl;
+  SymbolContext m_sym_ctx;
+};
+} // namespace
+
+SymbolContextList ClangExpressionDeclMap::SearchFunctionsInSymbolContexts(
+    const SymbolContextList &sc_list,
+    const CompilerDeclContext &frame_decl_context) {
+  // First, symplify things by looping through the symbol contexts to
+  // remove unwanted functions and separate out the functions we want to
+  // compare and prune into a separate list. Cache the info needed about
+  // the function declarations in a vector for efficiency.
+  uint32_t num_indices = sc_list.GetSize();
+  SymbolContextList sc_sym_list;
+  std::vector<FuncDeclInfo> decl_infos;
+  decl_infos.reserve(num_indices);
+  clang::DeclContext *frame_decl_ctx =
+      (clang::DeclContext *)frame_decl_context.GetOpaqueDeclContext();
+  ClangASTContext *ast = llvm::dyn_cast_or_null<ClangASTContext>(
+      frame_decl_context.GetTypeSystem());
 
-      if (reg_info) {
-        LLDB_LOGF(log, "  CEDM::FEVD[%u] Found register %s", current_id,
-                  reg_info->name);
+  for (uint32_t index = 0; index < num_indices; ++index) {
+    FuncDeclInfo fdi;
+    SymbolContext sym_ctx;
+    sc_list.GetContextAtIndex(index, sym_ctx);
 
-        AddOneRegister(context, reg_info, current_id);
-      }
+    // We don't know enough about symbols to compare them, but we should
+    // keep them in the list.
+    Function *function = sym_ctx.function;
+    if (!function) {
+      sc_sym_list.Append(sym_ctx);
+      continue;
+    }
+    // Filter out functions without declaration contexts, as well as
+    // class/instance methods, since they'll be skipped in the code that
+    // follows anyway.
+    CompilerDeclContext func_decl_context = function->GetDeclContext();
+    if (!func_decl_context ||
+        func_decl_context.IsClassMethod(nullptr, nullptr, nullptr))
+      continue;
+    // We can only prune functions for which we can copy the type.
+    CompilerType func_clang_type = function->GetType()->GetFullCompilerType();
+    CompilerType copied_func_type = GuardedCopyType(func_clang_type);
+    if (!copied_func_type) {
+      sc_sym_list.Append(sym_ctx);
+      continue;
     }
-  } else {
-    ValueObjectSP valobj;
-    VariableSP var;
-
-    bool local_var_lookup =
-        !namespace_decl || (namespace_decl.GetName() ==
-                            ConstString(g_lldb_local_vars_namespace_cstr));
-    if (frame && local_var_lookup) {
-      CompilerDeclContext compiler_decl_context =
-          sym_ctx.block != nullptr ? sym_ctx.block->GetDeclContext()
-                                   : CompilerDeclContext();
-
-      if (compiler_decl_context) {
-        // Make sure that the variables are parsed so that we have the
-        // declarations.
-        VariableListSP vars = frame->GetInScopeVariableList(true);
-        for (size_t i = 0; i < vars->GetSize(); i++)
-          vars->GetVariableAtIndex(i)->GetDecl();
-
-        // Search for declarations matching the name. Do not include imported
-        // decls in the search if we are looking for decls in the artificial
-        // namespace $__lldb_local_vars.
-        std::vector<CompilerDecl> found_decls =
-            compiler_decl_context.FindDeclByName(name,
-                                                 namespace_decl.IsValid());
-
-        bool variable_found = false;
-        for (CompilerDecl decl : found_decls) {
-          for (size_t vi = 0, ve = vars->GetSize(); vi != ve; ++vi) {
-            VariableSP candidate_var = vars->GetVariableAtIndex(vi);
-            if (candidate_var->GetDecl() == decl) {
-              var = candidate_var;
-              break;
-            }
-          }
 
-          if (var && !variable_found) {
-            variable_found = true;
-            valobj = ValueObjectVariable::Create(frame, var);
-            AddOneVariable(context, var, valobj, current_id);
-            context.m_found.variable = true;
-          }
-        }
-        if (variable_found)
-          return;
-      }
+    fdi.m_sym_ctx = sym_ctx;
+    fdi.m_name = function->GetName();
+    fdi.m_copied_type = copied_func_type;
+    fdi.m_decl_lvl = LLDB_INVALID_DECL_LEVEL;
+    if (fdi.m_copied_type && func_decl_context) {
+      // Call CountDeclLevels to get the number of parent scopes we have
+      // to look through before we find the function declaration. When
+      // comparing functions of the same type, the one with a lower count
+      // will be closer to us in the lookup scope and shadows the other.
+      clang::DeclContext *func_decl_ctx =
+          (clang::DeclContext *)func_decl_context.GetOpaqueDeclContext();
+      fdi.m_decl_lvl = ast->CountDeclLevels(frame_decl_ctx, func_decl_ctx,
+                                            &fdi.m_name, &fdi.m_copied_type);
     }
-    if (target) {
-      var = FindGlobalVariable(*target, module_sp, name, &namespace_decl,
-                               nullptr);
+    decl_infos.emplace_back(fdi);
+  }
 
-      if (var) {
-        valobj = ValueObjectVariable::Create(target, var);
-        AddOneVariable(context, var, valobj, current_id);
-        context.m_found.variable = true;
-        return;
-      }
+  // Loop through the functions in our cache looking for matching types,
+  // then compare their scope levels to see which is closer.
+  std::multimap<CompilerType, const FuncDeclInfo *> matches;
+  for (const FuncDeclInfo &fdi : decl_infos) {
+    const CompilerType t = fdi.m_copied_type;
+    auto q = matches.find(t);
+    if (q != matches.end()) {
+      if (q->second->m_decl_lvl > fdi.m_decl_lvl)
+        // This function is closer; remove the old set.
+        matches.erase(t);
+      else if (q->second->m_decl_lvl < fdi.m_decl_lvl)
+        // The functions in our set are closer - skip this one.
+        continue;
     }
+    matches.insert(std::make_pair(t, &fdi));
+  }
 
-    std::vector<clang::NamedDecl *> decls_from_modules;
+  // Loop through our matches and add their symbol contexts to our list.
+  SymbolContextList sc_func_list;
+  for (const auto &q : matches)
+    sc_func_list.Append(q.second->m_sym_ctx);
 
-    if (target) {
-      if (ClangModulesDeclVendor *decl_vendor =
-              target->GetClangModulesDeclVendor()) {
-        decl_vendor->FindDecls(name, false, UINT32_MAX, decls_from_modules);
-      }
-    }
+  // Rejoin the lists with the functions in front.
+  sc_func_list.Append(sc_sym_list);
+  return sc_func_list;
+}
 
-    const bool include_inlines = false;
-    sc_list.Clear();
-    if (namespace_decl && module_sp) {
-      const bool include_symbols = false;
+void ClangExpressionDeclMap::LookupFunction(NameSearchContext &context,
+                                            lldb::ModuleSP module_sp,
+                                            ConstString name,
+                                            CompilerDeclContext &namespace_decl,
+                                            unsigned current_id) {
+  if (!m_parser_vars)
+    return;
 
-      module_sp->FindFunctions(name, &namespace_decl, eFunctionNameTypeBase,
-                               include_symbols, include_inlines, sc_list);
-    } else if (target && !namespace_decl) {
-      const bool include_symbols = true;
+  Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
 
-      // TODO Fix FindFunctions so that it doesn't return
-      //   instance methods for eFunctionNameTypeBase.
+  std::vector<clang::NamedDecl *> decls_from_modules;
 
-      target->GetImages().FindFunctions(name, eFunctionNameTypeFull,
-                                        include_symbols, include_inlines,
-                                        sc_list);
+  if (target) {
+    if (ClangModulesDeclVendor *decl_vendor =
+            target->GetClangModulesDeclVendor()) {
+      decl_vendor->FindDecls(name, false, UINT32_MAX, decls_from_modules);
     }
+  }
 
-    // If we found more than one function, see if we can use the frame's decl
-    // context to remove functions that are shadowed by other functions which
-    // match in type but are nearer in scope.
-    //
-    // AddOneFunction will not add a function whose type has already been
-    // added, so if there's another function in the list with a matching type,
-    // check to see if their decl context is a parent of the current frame's or
-    // was imported via a and using statement, and pick the best match
-    // according to lookup rules.
-    if (sc_list.GetSize() > 1) {
-      // Collect some info about our frame's context.
-      StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
-      SymbolContext frame_sym_ctx;
-      if (frame != nullptr)
-        frame_sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
-                                                lldb::eSymbolContextBlock);
-      CompilerDeclContext frame_decl_context =
-          frame_sym_ctx.block != nullptr ? frame_sym_ctx.block->GetDeclContext()
-                                         : CompilerDeclContext();
-
-      // We can't do this without a compiler decl context for our frame.
-      if (frame_decl_context) {
-        clang::DeclContext *frame_decl_ctx =
-            (clang::DeclContext *)frame_decl_context.GetOpaqueDeclContext();
-        ClangASTContext *ast = llvm::dyn_cast_or_null<ClangASTContext>(
-            frame_decl_context.GetTypeSystem());
-
-        // Structure to hold the info needed when comparing function
-        // declarations.
-        struct FuncDeclInfo {
-          ConstString m_name;
-          CompilerType m_copied_type;
-          uint32_t m_decl_lvl;
-          SymbolContext m_sym_ctx;
-        };
-
-        // First, symplify things by looping through the symbol contexts to
-        // remove unwanted functions and separate out the functions we want to
-        // compare and prune into a separate list. Cache the info needed about
-        // the function declarations in a vector for efficiency.
-        SymbolContextList sc_sym_list;
-        uint32_t num_indices = sc_list.GetSize();
-        std::vector<FuncDeclInfo> fdi_cache;
-        fdi_cache.reserve(num_indices);
-        for (uint32_t index = 0; index < num_indices; ++index) {
-          FuncDeclInfo fdi;
-          SymbolContext sym_ctx;
-          sc_list.GetContextAtIndex(index, sym_ctx);
-
-          // We don't know enough about symbols to compare them, but we should
-          // keep them in the list.
-          Function *function = sym_ctx.function;
-          if (!function) {
-            sc_sym_list.Append(sym_ctx);
-            continue;
-          }
-          // Filter out functions without declaration contexts, as well as
-          // class/instance methods, since they'll be skipped in the code that
-          // follows anyway.
-          CompilerDeclContext func_decl_context = function->GetDeclContext();
-          if (!func_decl_context ||
-              func_decl_context.IsClassMethod(nullptr, nullptr, nullptr))
-            continue;
-          // We can only prune functions for which we can copy the type.
-          CompilerType func_clang_type =
-              function->GetType()->GetFullCompilerType();
-          CompilerType copied_func_type = GuardedCopyType(func_clang_type);
-          if (!copied_func_type) {
-            sc_sym_list.Append(sym_ctx);
-            continue;
-          }
+  const bool include_inlines = false;
+  SymbolContextList sc_list;
+  if (namespace_decl && module_sp) {
+    const bool include_symbols = false;
 
-          fdi.m_sym_ctx = sym_ctx;
-          fdi.m_name = function->GetName();
-          fdi.m_copied_type = copied_func_type;
-          fdi.m_decl_lvl = LLDB_INVALID_DECL_LEVEL;
-          if (fdi.m_copied_type && func_decl_context) {
-            // Call CountDeclLevels to get the number of parent scopes we have
-            // to look through before we find the function declaration. When
-            // comparing functions of the same type, the one with a lower count
-            // will be closer to us in the lookup scope and shadows the other.
-            clang::DeclContext *func_decl_ctx =
-                (clang::DeclContext *)func_decl_context.GetOpaqueDeclContext();
-            fdi.m_decl_lvl = ast->CountDeclLevels(
-                frame_decl_ctx, func_decl_ctx, &fdi.m_name, &fdi.m_copied_type);
-          }
-          fdi_cache.emplace_back(fdi);
-        }
+    module_sp->FindFunctions(name, &namespace_decl, eFunctionNameTypeBase,
+                             include_symbols, include_inlines, sc_list);
+  } else if (target && !namespace_decl) {
+    const bool include_symbols = true;
 
-        // Loop through the functions in our cache looking for matching types,
-        // then compare their scope levels to see which is closer.
-        std::multimap<CompilerType, const FuncDeclInfo *> matches;
-        for (const FuncDeclInfo &fdi : fdi_cache) {
-          const CompilerType t = fdi.m_copied_type;
-          auto q = matches.find(t);
-          if (q != matches.end()) {
-            if (q->second->m_decl_lvl > fdi.m_decl_lvl)
-              // This function is closer; remove the old set.
-              matches.erase(t);
-            else if (q->second->m_decl_lvl < fdi.m_decl_lvl)
-              // The functions in our set are closer - skip this one.
-              continue;
-          }
-          matches.insert(std::make_pair(t, &fdi));
-        }
+    // TODO Fix FindFunctions so that it doesn't return
+    //   instance methods for eFunctionNameTypeBase.
 
-        // Loop through our matches and add their symbol contexts to our list.
-        SymbolContextList sc_func_list;
-        for (const auto &q : matches)
-          sc_func_list.Append(q.second->m_sym_ctx);
+    target->GetImages().FindFunctions(
+        name, eFunctionNameTypeFull | eFunctionNameTypeBase, include_symbols,
+        include_inlines, sc_list);
+  }
 
-        // Rejoin the lists with the functions in front.
-        sc_list = sc_func_list;
-        sc_list.Append(sc_sym_list);
-      }
+  // If we found more than one function, see if we can use the frame's decl
+  // context to remove functions that are shadowed by other functions which
+  // match in type but are nearer in scope.
+  //
+  // AddOneFunction will not add a function whose type has already been
+  // added, so if there's another function in the list with a matching type,
+  // check to see if their decl context is a parent of the current frame's or
+  // was imported via a and using statement, and pick the best match
+  // according to lookup rules.
+  if (sc_list.GetSize() > 1) {
+    // Collect some info about our frame's context.
+    StackFrame *frame = m_parser_vars->m_exe_ctx.GetFramePtr();
+    SymbolContext frame_sym_ctx;
+    if (frame != nullptr)
+      frame_sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
+                                              lldb::eSymbolContextBlock);
+    CompilerDeclContext frame_decl_context =
+        frame_sym_ctx.block != nullptr ? frame_sym_ctx.block->GetDeclContext()
+                                       : CompilerDeclContext();
+
+    // We can't do this without a compiler decl context for our frame.
+    if (frame_decl_context) {
+      sc_list = SearchFunctionsInSymbolContexts(sc_list, frame_decl_context);
     }
+  }
 
-    if (sc_list.GetSize()) {
-      Symbol *extern_symbol = nullptr;
-      Symbol *non_extern_symbol = nullptr;
-
-      for (uint32_t index = 0, num_indices = sc_list.GetSize();
-           index < num_indices; ++index) {
-        SymbolContext sym_ctx;
-        sc_list.GetContextAtIndex(index, sym_ctx);
+  if (sc_list.GetSize()) {
+    Symbol *extern_symbol = nullptr;
+    Symbol *non_extern_symbol = nullptr;
 
-        if (sym_ctx.function) {
-          CompilerDeclContext decl_ctx = sym_ctx.function->GetDeclContext();
+    for (uint32_t index = 0, num_indices = sc_list.GetSize();
+         index < num_indices; ++index) {
+      SymbolContext sym_ctx;
+      sc_list.GetContextAtIndex(index, sym_ctx);
 
-          if (!decl_ctx)
-            continue;
+      if (sym_ctx.function) {
+        CompilerDeclContext decl_ctx = sym_ctx.function->GetDeclContext();
 
-          // Filter out class/instance methods.
-          if (decl_ctx.IsClassMethod(nullptr, nullptr, nullptr))
-            continue;
+        if (!decl_ctx)
+          continue;
 
-          AddOneFunction(context, sym_ctx.function, nullptr, current_id);
-          context.m_found.function_with_type_info = true;
-          context.m_found.function = true;
-        } else if (sym_ctx.symbol) {
-          if (sym_ctx.symbol->GetType() == eSymbolTypeReExported && target) {
-            sym_ctx.symbol = sym_ctx.symbol->ResolveReExportedSymbol(*target);
-            if (sym_ctx.symbol == nullptr)
-              continue;
-          }
+        // Filter out class/instance methods.
+        if (decl_ctx.IsClassMethod(nullptr, nullptr, nullptr))
+          continue;
 
-          if (sym_ctx.symbol->IsExternal())
-            extern_symbol = sym_ctx.symbol;
-          else
-            non_extern_symbol = sym_ctx.symbol;
+        AddOneFunction(context, sym_ctx.function, nullptr, current_id);
+        context.m_found.function_with_type_info = true;
+        context.m_found.function = true;
+      } else if (sym_ctx.symbol) {
+        if (sym_ctx.symbol->GetType() == eSymbolTypeReExported && target) {
+          sym_ctx.symbol = sym_ctx.symbol->ResolveReExportedSymbol(*target);
+          if (sym_ctx.symbol == nullptr)
+            continue;
         }
+
+        if (sym_ctx.symbol->IsExternal())
+          extern_symbol = sym_ctx.symbol;
+        else
+          non_extern_symbol = sym_ctx.symbol;
       }
+    }
 
-      if (!context.m_found.function_with_type_info) {
-        for (clang::NamedDecl *decl : decls_from_modules) {
-          if (llvm::isa<clang::FunctionDecl>(decl)) {
-            clang::NamedDecl *copied_decl =
-                llvm::cast_or_null<FunctionDecl>(CopyDecl(decl));
-            if (copied_decl) {
-              context.AddNamedDecl(copied_decl);
-              context.m_found.function_with_type_info = true;
-            }
+    if (!context.m_found.function_with_type_info) {
+      for (clang::NamedDecl *decl : decls_from_modules) {
+        if (llvm::isa<clang::FunctionDecl>(decl)) {
+          clang::NamedDecl *copied_decl =
+              llvm::cast_or_null<FunctionDecl>(CopyDecl(decl));
+          if (copied_decl) {
+            context.AddNamedDecl(copied_decl);
+            context.m_found.function_with_type_info = true;
           }
         }
       }
+    }
 
-      if (!context.m_found.function_with_type_info) {
-        if (extern_symbol) {
-          AddOneFunction(context, nullptr, extern_symbol, current_id);
-          context.m_found.function = true;
-        } else if (non_extern_symbol) {
-          AddOneFunction(context, nullptr, non_extern_symbol, current_id);
-          context.m_found.function = true;
-        }
+    if (!context.m_found.function_with_type_info) {
+      if (extern_symbol) {
+        AddOneFunction(context, nullptr, extern_symbol, current_id);
+        context.m_found.function = true;
+      } else if (non_extern_symbol) {
+        AddOneFunction(context, nullptr, non_extern_symbol, current_id);
+        context.m_found.function = true;
       }
     }
+  }
+}
 
-    if (!context.m_found.function_with_type_info) {
-      // Try the modules next.
+void ClangExpressionDeclMap::FindExternalVisibleDecls(
+    NameSearchContext &context, lldb::ModuleSP module_sp,
+    CompilerDeclContext &namespace_decl, unsigned int current_id) {
+  assert(m_ast_context);
 
-      do {
-        if (ClangModulesDeclVendor *modules_decl_vendor =
-                m_target->GetClangModulesDeclVendor()) {
-          bool append = false;
-          uint32_t max_matches = 1;
-          std::vector<clang::NamedDecl *> decls;
+  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
-          if (!modules_decl_vendor->FindDecls(name, append, max_matches, decls))
-            break;
+  const ConstString name(context.m_decl_name.getAsString().c_str());
+  if (IgnoreName(name, false))
+    return;
 
-          clang::NamedDecl *const decl_from_modules = decls[0];
+  // Only look for functions by name out in our symbols if the function doesn't
+  // start with our phony prefix of '$'
 
-          if (llvm::isa<clang::FunctionDecl>(decl_from_modules)) {
-            if (log) {
-              LLDB_LOGF(log,
-                        "  CAS::FEVD[%u] Matching function found for "
-                        "\"%s\" in the modules",
-                        current_id, name.GetCString());
-            }
+  Target *target = nullptr;
+  StackFrame *frame = nullptr;
+  SymbolContext sym_ctx;
+  if (m_parser_vars) {
+    target = m_parser_vars->m_exe_ctx.GetTargetPtr();
+    frame = m_parser_vars->m_exe_ctx.GetFramePtr();
+  }
+  if (frame != nullptr)
+    sym_ctx = frame->GetSymbolContext(lldb::eSymbolContextFunction |
+                                      lldb::eSymbolContextBlock);
 
-            clang::Decl *copied_decl = CopyDecl(decl_from_modules);
-            clang::FunctionDecl *copied_function_decl =
-                copied_decl ? dyn_cast<clang::FunctionDecl>(copied_decl)
-                            : nullptr;
+  // Try the persistent decls, which take precedence over all else.
+  if (!namespace_decl)
+    SearchPersistenDecls(context, name, current_id);
 
-            if (!copied_function_decl) {
-              LLDB_LOGF(log,
-                        "  CAS::FEVD[%u] - Couldn't export a function "
-                        "declaration from the modules",
-                        current_id);
+  if (name.GetStringRef().startswith("$") && !namespace_decl) {
+    if (name == "$__lldb_class") {
+      LookUpLldbClass(context, current_id);
+      return;
+    }
 
-              break;
-            }
+    if (name == "$__lldb_objc_class") {
+      LookUpLldbObjCClass(context, current_id);
+      return;
+    }
+    if (name == g_lldb_local_vars_namespace_cstr) {
+      LookupLocalVarNamespace(sym_ctx, context);
+      return;
+    }
+
+    // any other $__lldb names should be weeded out now
+    if (name.GetStringRef().startswith("$__lldb"))
+      return;
 
-            MaybeRegisterFunctionBody(copied_function_decl);
+    // No ParserVars means we can't do register or variable lookup.
+    if (!m_parser_vars || !m_parser_vars->m_persistent_vars)
+      return;
 
-            context.AddNamedDecl(copied_function_decl);
+    ExpressionVariableSP pvar_sp(
+        m_parser_vars->m_persistent_vars->GetVariable(name));
 
-            context.m_found.function_with_type_info = true;
-            context.m_found.function = true;
-          } else if (llvm::isa<clang::VarDecl>(decl_from_modules)) {
-            if (log) {
-              LLDB_LOGF(log,
-                        "  CAS::FEVD[%u] Matching variable found for "
-                        "\"%s\" in the modules",
-                        current_id, name.GetCString());
-            }
+    if (pvar_sp) {
+      AddOneVariable(context, pvar_sp, current_id);
+      return;
+    }
 
-            clang::Decl *copied_decl = CopyDecl(decl_from_modules);
-            clang::VarDecl *copied_var_decl =
-                copied_decl ? dyn_cast_or_null<clang::VarDecl>(copied_decl)
-                            : nullptr;
+    assert(name.GetStringRef().startswith("$"));
+    llvm::StringRef reg_name = name.GetStringRef().substr(1);
 
-            if (!copied_var_decl) {
-              LLDB_LOGF(log,
-                        "  CAS::FEVD[%u] - Couldn't export a variable "
-                        "declaration from the modules",
-                        current_id);
+    if (m_parser_vars->m_exe_ctx.GetRegisterContext()) {
+      const RegisterInfo *reg_info(
+          m_parser_vars->m_exe_ctx.GetRegisterContext()->GetRegisterInfoByName(
+              reg_name));
 
-              break;
-            }
+      if (reg_info) {
+        LLDB_LOGF(log, "  CEDM::FEVD[%u] Found register %s", current_id,
+                  reg_info->name);
 
-            context.AddNamedDecl(copied_var_decl);
+        AddOneRegister(context, reg_info, current_id);
+      }
+    }
+    return;
+  }
 
-            context.m_found.variable = true;
-          }
-        }
-      } while (false);
+  bool local_var_lookup = !namespace_decl || (namespace_decl.GetName() ==
+                                              g_lldb_local_vars_namespace_cstr);
+  if (frame && local_var_lookup)
+    if (LookupLocalVariable(context, name, current_id, sym_ctx, namespace_decl))
+      return;
+
+  if (target) {
+    ValueObjectSP valobj;
+    VariableSP var;
+    var = FindGlobalVariable(*target, module_sp, name, &namespace_decl);
+
+    if (var) {
+      valobj = ValueObjectVariable::Create(target, var);
+      AddOneVariable(context, var, valobj, current_id);
+      context.m_found.variable = true;
+      return;
     }
+  }
 
-    if (target && !context.m_found.variable && !namespace_decl) {
-      // We couldn't find a non-symbol variable for this.  Now we'll hunt for a
-      // generic data symbol, and -- if it is found -- treat it as a variable.
-      Status error;
+  LookupFunction(context, module_sp, name, namespace_decl, current_id);
 
-      const Symbol *data_symbol =
-          m_parser_vars->m_sym_ctx.FindBestGlobalDataSymbol(name, error);
+  // Try the modules next.
+  if (!context.m_found.function_with_type_info)
+    LookupInModulesDeclVendor(context, name, current_id);
 
-      if (!error.Success()) {
-        const unsigned diag_id =
-            m_ast_context->getDiagnostics().getCustomDiagID(
-                clang::DiagnosticsEngine::Level::Error, "%0");
-        m_ast_context->getDiagnostics().Report(diag_id) << error.AsCString();
-      }
+  if (target && !context.m_found.variable && !namespace_decl) {
+    // We couldn't find a non-symbol variable for this.  Now we'll hunt for a
+    // generic data symbol, and -- if it is found -- treat it as a variable.
+    Status error;
 
-      if (data_symbol) {
-        std::string warning("got name from symbols: ");
-        warning.append(name.AsCString());
-        const unsigned diag_id =
-            m_ast_context->getDiagnostics().getCustomDiagID(
-                clang::DiagnosticsEngine::Level::Warning, "%0");
-        m_ast_context->getDiagnostics().Report(diag_id) << warning.c_str();
-        AddOneGenericVariable(context, *data_symbol, current_id);
-        context.m_found.variable = true;
-      }
+    const Symbol *data_symbol =
+        m_parser_vars->m_sym_ctx.FindBestGlobalDataSymbol(name, error);
+
+    if (!error.Success()) {
+      const unsigned diag_id =
+          m_ast_context->getDiagnostics().getCustomDiagID(
+              clang::DiagnosticsEngine::Level::Error, "%0");
+      m_ast_context->getDiagnostics().Report(diag_id) << error.AsCString();
+    }
+
+    if (data_symbol) {
+      std::string warning("got name from symbols: ");
+      warning.append(name.AsCString());
+      const unsigned diag_id =
+          m_ast_context->getDiagnostics().getCustomDiagID(
+              clang::DiagnosticsEngine::Level::Warning, "%0");
+      m_ast_context->getDiagnostics().Report(diag_id) << warning.c_str();
+      AddOneGenericVariable(context, *data_symbol, current_id);
+      context.m_found.variable = true;
     }
   }
 }
@@ -1543,15 +1508,6 @@ bool ClangExpressionDeclMap::GetVariableValue(VariableSP &var,
     return false;
   }
 
-  ASTContext *ast = clang_ast->getASTContext();
-
-  if (!ast) {
-    if (log)
-      log->PutCString(
-          "There is no AST context for the current execution context");
-    return false;
-  }
-
   DWARFExpression &var_location_expr = var->LocationExpression();
 
   Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
@@ -1664,14 +1620,10 @@ void ClangExpressionDeclMap::AddOneVariable(NameSearchContext &context,
   if (is_reference)
     entity->m_flags |= ClangExpressionVariable::EVTypeIsReference;
 
-  if (log) {
-    ASTDumper orig_dumper(ut.GetOpaqueQualType());
-    ASTDumper ast_dumper(var_decl);
-    LLDB_LOGF(log,
-              "  CEDM::FEVD[%u] Found variable %s, returned %s (original %s)",
-              current_id, decl_name.c_str(), ast_dumper.GetCString(),
-              orig_dumper.GetCString());
-  }
+  LLDB_LOG(log,
+           "  CEDM::FEVD[{0}] Found variable {1}, returned\n{2} (original {3})",
+           current_id, decl_name, ClangUtil::DumpDecl(var_decl),
+           ClangUtil::ToString(ut));
 }
 
 void ClangExpressionDeclMap::AddOneVariable(NameSearchContext &context,
@@ -1703,11 +1655,8 @@ void ClangExpressionDeclMap::AddOneVariable(NameSearchContext &context,
   parser_vars->m_llvm_value = nullptr;
   parser_vars->m_lldb_value.Clear();
 
-  if (log) {
-    ASTDumper ast_dumper(var_decl);
-    LLDB_LOGF(log, "  CEDM::FEVD[%u] Added pvar %s, returned %s", current_id,
-              pvar_sp->GetName().GetCString(), ast_dumper.GetCString());
-  }
+  LLDB_LOG(log, "  CEDM::FEVD[{0}] Added pvar {1}, returned\n{2}", current_id,
+           pvar_sp->GetName(), ClangUtil::DumpDecl(var_decl));
 }
 
 void ClangExpressionDeclMap::AddOneGenericVariable(NameSearchContext &context,
@@ -1722,17 +1671,16 @@ void ClangExpressionDeclMap::AddOneGenericVariable(NameSearchContext &context,
   if (target == nullptr)
     return;
 
-  ASTContext *scratch_ast_context =
-      target->GetScratchClangASTContext()->getASTContext();
+  ClangASTContext *scratch_ast_context = ClangASTContext::GetScratch(*target);
+  if (!scratch_ast_context)
+    return;
 
-  TypeFromUser user_type(
-      ClangASTContext::GetBasicType(scratch_ast_context, eBasicTypeVoid)
-          .GetPointerType()
-          .GetLValueReferenceType());
-  TypeFromParser parser_type(
-      ClangASTContext::GetBasicType(m_ast_context, eBasicTypeVoid)
-          .GetPointerType()
-          .GetLValueReferenceType());
+  TypeFromUser user_type(scratch_ast_context->GetBasicType(eBasicTypeVoid)
+                             .GetPointerType()
+                             .GetLValueReferenceType());
+  TypeFromParser parser_type(m_clang_ast_context->GetBasicType(eBasicTypeVoid)
+                                 .GetPointerType()
+                                 .GetLValueReferenceType());
   NamedDecl *var_decl = context.AddVarDecl(parser_type);
 
   std::string decl_name(context.m_decl_name.getAsString());
@@ -1761,86 +1709,8 @@ void ClangExpressionDeclMap::AddOneGenericVariable(NameSearchContext &context,
   parser_vars->m_llvm_value = nullptr;
   parser_vars->m_lldb_sym = &symbol;
 
-  if (log) {
-    ASTDumper ast_dumper(var_decl);
-
-    LLDB_LOGF(log, "  CEDM::FEVD[%u] Found variable %s, returned %s",
-              current_id, decl_name.c_str(), ast_dumper.GetCString());
-  }
-}
-
-bool ClangExpressionDeclMap::ResolveUnknownTypes() {
-  Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
-  Target *target = m_parser_vars->m_exe_ctx.GetTargetPtr();
-
-  ClangASTContextForExpressions *scratch_ast_context =
-      static_cast<ClangASTContextForExpressions *>(
-          target->GetScratchClangASTContext());
-
-  for (size_t index = 0, num_entities = m_found_entities.GetSize();
-       index < num_entities; ++index) {
-    ExpressionVariableSP entity = m_found_entities.GetVariableAtIndex(index);
-
-    ClangExpressionVariable::ParserVars *parser_vars =
-        llvm::cast<ClangExpressionVariable>(entity.get())
-            ->GetParserVars(GetParserID());
-
-    if (entity->m_flags & ClangExpressionVariable::EVUnknownType) {
-      const NamedDecl *named_decl = parser_vars->m_named_decl;
-      const VarDecl *var_decl = dyn_cast<VarDecl>(named_decl);
-
-      if (!var_decl) {
-        LLDB_LOGF(log, "Entity of unknown type does not have a VarDecl");
-        return false;
-      }
-
-      if (log) {
-        ASTDumper ast_dumper(const_cast<VarDecl *>(var_decl));
-        LLDB_LOGF(log, "Variable of unknown type now has Decl %s",
-                  ast_dumper.GetCString());
-      }
-
-      QualType var_type = var_decl->getType();
-      TypeFromParser parser_type(
-          var_type.getAsOpaquePtr(),
-          ClangASTContext::GetASTContext(&var_decl->getASTContext()));
-
-      lldb::opaque_compiler_type_t copied_type = nullptr;
-      if (m_ast_importer_sp) {
-        copied_type = m_ast_importer_sp->CopyType(
-            scratch_ast_context->getASTContext(), &var_decl->getASTContext(),
-            var_type.getAsOpaquePtr());
-      } else if (HasMerger()) {
-        copied_type = CopyTypeWithMerger(
-                          var_decl->getASTContext(),
-                          scratch_ast_context->GetMergerUnchecked(), var_type)
-                          .getAsOpaquePtr();
-      } else {
-        lldbassert(0 && "No mechanism to copy a resolved unknown type!");
-        return false;
-      }
-
-      if (!copied_type) {
-        LLDB_LOGF(log, "ClangExpressionDeclMap::ResolveUnknownType - Couldn't "
-                       "import the type for a variable");
-
-        return (bool)lldb::ExpressionVariableSP();
-      }
-
-      TypeFromUser user_type(copied_type, scratch_ast_context);
-
-      //            parser_vars->m_lldb_value.SetContext(Value::eContextTypeClangType,
-      //            user_type.GetOpaqueQualType());
-      parser_vars->m_lldb_value.SetCompilerType(user_type);
-      parser_vars->m_parser_type = parser_type;
-
-      entity->SetCompilerType(user_type);
-
-      entity->m_flags &= ~(ClangExpressionVariable::EVUnknownType);
-    }
-  }
-
-  return true;
+  LLDB_LOG(log, "  CEDM::FEVD[{0}] Found variable {1}, returned\n{2}",
+           current_id, decl_name, ClangUtil::DumpDecl(var_decl));
 }
 
 void ClangExpressionDeclMap::AddOneRegister(NameSearchContext &context,
@@ -1849,8 +1719,8 @@ void ClangExpressionDeclMap::AddOneRegister(NameSearchContext &context,
   Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));
 
   CompilerType clang_type =
-      ClangASTContext::GetBuiltinTypeForEncodingAndBitSize(
-          m_ast_context, reg_info->encoding, reg_info->byte_size * 8);
+      m_clang_ast_context->GetBuiltinTypeForEncodingAndBitSize(
+          reg_info->encoding, reg_info->byte_size * 8);
 
   if (!clang_type) {
     LLDB_LOGF(log, "  Tried to add a type for %s, but couldn't get one",
@@ -1880,12 +1750,9 @@ void ClangExpressionDeclMap::AddOneRegister(NameSearchContext &context,
   parser_vars->m_lldb_value.Clear();
   entity->m_flags |= ClangExpressionVariable::EVBareRegister;
 
-  if (log) {
-    ASTDumper ast_dumper(var_decl);
-    LLDB_LOGF(log, "  CEDM::FEVD[%d] Added register %s, returned %s",
-              current_id, context.m_decl_name.getAsString().c_str(),
-              ast_dumper.GetCString());
-  }
+  LLDB_LOG(log, "  CEDM::FEVD[{0}] Added register {1}, returned\n{2}",
+           current_id, context.m_decl_name.getAsString(),
+           ClangUtil::DumpDecl(var_decl));
 }
 
 void ClangExpressionDeclMap::AddOneFunction(NameSearchContext &context,
@@ -1928,17 +1795,16 @@ void ClangExpressionDeclMap::AddOneFunction(NameSearchContext &context,
                   CopyDecl(function_template));
           if (copied_function_template) {
             if (log) {
-              ASTDumper ast_dumper((clang::Decl *)copied_function_template);
-
               StreamString ss;
 
               function->DumpSymbolContext(&ss);
 
-              log->Printf("  CEDM::FEVD[%u] Imported decl for function template"
-                          " %s (description %s), returned %s",
-                          current_id,
-                          copied_function_template->getNameAsString().c_str(),
-                          ss.GetData(), ast_dumper.GetCString());
+              LLDB_LOG(log,
+                       "  CEDM::FEVD[{0}] Imported decl for function template"
+                       " {1} (description {2}), returned\n{3}",
+                       current_id, copied_function_template->getNameAsString(),
+                       ss.GetData(),
+                       ClangUtil::DumpDecl(copied_function_template));
             }
 
             context.AddNamedDecl(copied_function_template);
@@ -1948,18 +1814,15 @@ void ClangExpressionDeclMap::AddOneFunction(NameSearchContext &context,
                   llvm::dyn_cast_or_null<clang::FunctionDecl>(
                       CopyDecl(src_function_decl))) {
             if (log) {
-              ASTDumper ast_dumper((clang::Decl *)copied_function_decl);
-
               StreamString ss;
 
               function->DumpSymbolContext(&ss);
 
-              LLDB_LOGF(log,
-                        "  CEDM::FEVD[%u] Imported decl for function %s "
-                        "(description %s), returned %s",
-                        current_id,
-                        copied_function_decl->getNameAsString().c_str(),
-                        ss.GetData(), ast_dumper.GetCString());
+              LLDB_LOG(log,
+                       "  CEDM::FEVD[{0}]] Imported decl for function {1} "
+                       "(description {2}), returned\n{3}",
+                       current_id, copied_function_decl->getNameAsString(),
+                       ss.GetData(), ClangUtil::DumpDecl(copied_function_decl));
             }
 
             context.AddNamedDecl(copied_function_decl);
@@ -2061,20 +1924,17 @@ void ClangExpressionDeclMap::AddOneFunction(NameSearchContext &context,
   parser_vars->m_llvm_value = nullptr;
 
   if (log) {
-    std::string function_str =
-        function_decl ? ASTDumper(function_decl).GetCString() : "nullptr";
-
     StreamString ss;
 
     fun_address.Dump(&ss,
                      m_parser_vars->m_exe_ctx.GetBestExecutionContextScope(),
                      Address::DumpStyleResolvedDescription);
 
-    LLDB_LOGF(
-        log,
-        "  CEDM::FEVD[%u] Found %s function %s (description %s), returned %s",
-        current_id, (function ? "specific" : "generic"), decl_name.c_str(),
-        ss.GetData(), function_str.c_str());
+    LLDB_LOG(log,
+             "  CEDM::FEVD[{0}] Found {1} function {2} (description {3}), "
+             "returned\n{4}",
+             current_id, (function ? "specific" : "generic"), decl_name,
+             ss.GetData(), ClangUtil::DumpDecl(function_decl));
   }
 }
 
@@ -2097,11 +1957,11 @@ void ClangExpressionDeclMap::AddThisType(NameSearchContext &context,
   if (copied_clang_type.IsAggregateType() &&
       copied_clang_type.GetCompleteType()) {
     CompilerType void_clang_type =
-        ClangASTContext::GetBasicType(m_ast_context, eBasicTypeVoid);
+        m_clang_ast_context->GetBasicType(eBasicTypeVoid);
     CompilerType void_ptr_clang_type = void_clang_type.GetPointerType();
 
-    CompilerType method_type = ClangASTContext::CreateFunctionType(
-        m_ast_context, void_clang_type, &void_ptr_clang_type, 1, false, 0);
+    CompilerType method_type = m_clang_ast_context->CreateFunctionType(
+        void_clang_type, &void_ptr_clang_type, 1, false, 0);
 
     const bool is_virtual = false;
     const bool is_static = false;
@@ -2110,22 +1970,16 @@ void ClangExpressionDeclMap::AddThisType(NameSearchContext &context,
     const bool is_attr_used = true;
     const bool is_artificial = false;
 
-    CXXMethodDecl *method_decl =
-        ClangASTContext::GetASTContext(m_ast_context)
-            ->AddMethodToCXXRecordType(
-                copied_clang_type.GetOpaqueQualType(), "$__lldb_expr", nullptr,
-                method_type, lldb::eAccessPublic, is_virtual, is_static,
-                is_inline, is_explicit, is_attr_used, is_artificial);
-
-    if (log) {
-      ASTDumper method_ast_dumper((clang::Decl *)method_decl);
-      ASTDumper type_ast_dumper(copied_clang_type);
+    CXXMethodDecl *method_decl = m_clang_ast_context->AddMethodToCXXRecordType(
+        copied_clang_type.GetOpaqueQualType(), "$__lldb_expr", nullptr,
+        method_type, lldb::eAccessPublic, is_virtual, is_static, is_inline,
+        is_explicit, is_attr_used, is_artificial);
 
-      LLDB_LOGF(log,
-                "  CEDM::AddThisType Added function $__lldb_expr "
-                "(description %s) for this type %s",
-                method_ast_dumper.GetCString(), type_ast_dumper.GetCString());
-    }
+    LLDB_LOG(log,
+             "  CEDM::AddThisType Added function $__lldb_expr "
+             "(description {0}) for this type\n{1}",
+             ClangUtil::ToString(copied_clang_type),
+             ClangUtil::DumpDecl(method_decl));
   }
 
   if (!copied_clang_type.IsValid())
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
index 2711e90726e74..722f5e15a2aa2 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.h
@@ -63,12 +63,15 @@ public:
   ///     the result persistent variable, and instead marks the variable
   ///     as persisting.
   ///
-  /// \param[in] delegate
+  /// \param[in] result_delegate
   ///     If non-NULL, use this delegate to report result values.  This
   ///     allows the client ClangUserExpression to report a result.
   ///
-  /// \param[in] exe_ctx
-  ///     The execution context to use when parsing.
+  /// \param[in] target
+  ///     The target to use when parsing.
+  ///
+  /// \param[in] importer
+  ///     The ClangASTImporter to use when parsing.
   ///
   /// \param[in] ctx_obj
   ///     If not empty, then expression is evaluated in context of this object.
@@ -76,7 +79,7 @@ public:
   ClangExpressionDeclMap(
       bool keep_result_in_memory,
       Materializer::PersistentVariableDelegate *result_delegate,
-      ExecutionContext &exe_ctx,
+      const lldb::TargetSP &target, const lldb::ClangASTImporterSP &importer,
       ValueObject *ctx_obj);
 
   /// Destructor
@@ -98,13 +101,6 @@ public:
 
   void InstallCodeGenerator(clang::ASTConsumer *code_gen);
 
-  /// [Used by ClangExpressionParser] For each variable that had an unknown
-  ///     type at the beginning of parsing, determine its final type now.
-  ///
-  /// \return
-  ///     True on success; false otherwise.
-  bool ResolveUnknownTypes();
-
   /// Disable the state needed for parsing and IR transformation.
   void DidParse();
 
@@ -248,17 +244,6 @@ public:
   lldb::addr_t GetSymbolAddress(ConstString name,
                                 lldb::SymbolType symbol_type);
 
-  /// [Used by IRInterpreter] Get basic target information.
-  ///
-  /// \param[out] byte_order
-  ///     The byte order of the target.
-  ///
-  /// \param[out] address_byte_size
-  ///     The size of a pointer in bytes.
-  ///
-  /// \return
-  ///     True if the information could be determined; false
-  ///     otherwise.
   struct TargetInfo {
     lldb::ByteOrder byte_order;
     size_t address_byte_size;
@@ -276,9 +261,6 @@ public:
   ///
   /// \param[in] context
   ///     The NameSearchContext that can construct Decls for this name.
-  ///
-  /// \return
-  ///     True on success; false otherwise.
   void FindExternalVisibleDecls(NameSearchContext &context) override;
 
   /// Find all entities matching a given name in a given module/namespace,
@@ -296,14 +278,19 @@ public:
   /// \param[in] current_id
   ///     The ID for the current FindExternalVisibleDecls invocation,
   ///     for logging purposes.
-  ///
-  /// \return
-  ///     True on success; false otherwise.
   void FindExternalVisibleDecls(NameSearchContext &context,
                                 lldb::ModuleSP module,
                                 CompilerDeclContext &namespace_decl,
                                 unsigned int current_id);
 
+protected:
+  /// Retrieves the declaration with the given name from the storage of
+  /// persistent declarations.
+  ///
+  /// \return
+  ///     A persistent decl with the given name or a nullptr.
+  virtual clang::NamedDecl *GetPersistentDecl(ConstString name);
+
 private:
   ExpressionVariableList
       m_found_entities; ///< All entities that were looked up for the parser.
@@ -329,7 +316,7 @@ private:
       if (m_exe_ctx.GetTargetPtr())
         return m_exe_ctx.GetTargetPtr();
       else if (m_sym_ctx.target_sp)
-        m_sym_ctx.target_sp.get();
+        return m_sym_ctx.target_sp.get();
       return nullptr;
     }
 
@@ -396,6 +383,130 @@ private:
   /// from persistent variables.
   uint64_t GetParserID() { return (uint64_t) this; }
 
+  /// Should be called on all copied functions.
+  void MaybeRegisterFunctionBody(clang::FunctionDecl *copied_function_decl);
+
+  /// Searches the persistent decls of the target for entities with the
+  /// given name.
+  ///
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] name
+  ///     The name of the entities that need to be found.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  void SearchPersistenDecls(NameSearchContext &context, const ConstString name,
+                            unsigned int current_id);
+
+  /// Handles looking up $__lldb_class which requires special treatment.
+  ///
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  void LookUpLldbClass(NameSearchContext &context, unsigned int current_id);
+
+  /// Handles looking up $__lldb_objc_class which requires special treatment.
+  ///
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  void LookUpLldbObjCClass(NameSearchContext &context, unsigned int current_id);
+
+  /// Handles looking up the synthetic namespace that contains our local
+  /// variables for the current frame.
+  ///
+  /// \param[in] sym_ctx
+  ///     The current SymbolContext of this frame.
+  ///
+  /// \param[in] name_context
+  ///     The NameSearchContext that can construct Decls for this name.
+  void LookupLocalVarNamespace(SymbolContext &sym_ctx,
+                               NameSearchContext &name_context);
+
+  /// Lookup entities in the ClangModulesDeclVendor.
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] name
+  ///     The name of the entities that need to be found.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  void LookupInModulesDeclVendor(NameSearchContext &context, ConstString name,
+                                 unsigned current_id);
+
+  /// Looks up a local variable.
+  ///
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] name
+  ///     The name of the entities that need to be found.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  ///
+  /// \param[in] sym_ctx
+  ///     The current SymbolContext of this frame.
+  ///
+  /// \param[in] namespace_decl
+  ///     The parent namespace if there is one.
+  ///
+  /// \return
+  ///    True iff a local variable was found.
+  bool LookupLocalVariable(NameSearchContext &context, ConstString name,
+                           unsigned current_id, SymbolContext &sym_ctx,
+                           CompilerDeclContext &namespace_decl);
+
+  /// Searches for functions in the given SymbolContextList.
+  ///
+  /// \param[in] sc_list
+  ///     The SymbolContextList to search.
+  ///
+  /// \param[in] frame_decl_context
+  ///     The current DeclContext of the current frame.
+  ///
+  /// \return
+  ///     A SymbolContextList with any found functions in the front and
+  ///     any unknown SymbolContexts which are not functions in the back.
+  ///     The SymbolContexts for the functions are ordered by how close they are
+  ///     to the DeclContext for the given frame DeclContext.
+  SymbolContextList SearchFunctionsInSymbolContexts(
+      const SymbolContextList &sc_list,
+      const CompilerDeclContext &frame_decl_context);
+
+  /// Looks up a function.
+  ///
+  /// \param[in] context
+  ///     The NameSearchContext that can construct Decls for this name.
+  ///
+  /// \param[in] module_sp
+  ///     If non-NULL, the module to query.
+  ///
+  /// \param[in] name
+  ///     The name of the function that should be find.
+  ///
+  /// \param[in] namespace_decl
+  ///     If valid and module is non-NULL, the parent namespace.
+  ///
+  /// \param[in] current_id
+  ///     The ID for the current FindExternalVisibleDecls invocation,
+  ///     for logging purposes.
+  void LookupFunction(NameSearchContext &context, lldb::ModuleSP module_sp,
+                      ConstString name, CompilerDeclContext &namespace_decl,
+                      unsigned current_id);
+
   /// Given a target, find a variable that matches the given name and type.
   ///
   /// \param[in] target
@@ -410,17 +521,11 @@ private:
   /// \param[in] namespace_decl
   ///     If non-NULL and module is non-NULL, the parent namespace.
   ///
-  /// \param[in] type
-  ///     The required type for the variable.  This function may be called
-  ///     during parsing, in which case we don't know its type; hence the
-  ///     default.
-  ///
   /// \return
   ///     The LLDB Variable found, or NULL if none was found.
   lldb::VariableSP FindGlobalVariable(Target &target, lldb::ModuleSP &module,
                                       ConstString name,
-                                      CompilerDeclContext *namespace_decl,
-                                      TypeFromUser *type = nullptr);
+                                      CompilerDeclContext *namespace_decl);
 
   /// Get the value of a variable in a given execution context and return the
   /// associated Types if needed.
@@ -441,9 +546,6 @@ private:
   ///     AST context.  This is only useful when the variable is being
   ///     inspected on behalf of the parser, hence the default.
   ///
-  /// \param[in] decl
-  ///     The Decl to be looked up.
-  ///
   /// \return
   ///     Return true if the value was successfully filled in.
   bool GetVariableValue(lldb::VariableSP &var,
@@ -471,7 +573,7 @@ private:
   /// \param[in] context
   ///     The NameSearchContext to use when constructing the Decl.
   ///
-  /// \param[in] pvar
+  /// \param[in] pvar_sp
   ///     The persistent variable that needs a Decl.
   ///
   /// \param[in] current_id
@@ -483,12 +585,6 @@ private:
 
   /// Use the NameSearchContext to generate a Decl for the given LLDB symbol
   /// (treated as a variable), and put it in the list of found entities.
-  ///
-  /// \param[in] context
-  ///     The NameSearchContext to use when constructing the Decl.
-  ///
-  /// \param[in] var
-  ///     The LLDB Variable that needs a Decl.
   void AddOneGenericVariable(NameSearchContext &context, const Symbol &symbol,
                              unsigned int current_id);
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
index 1422911d6546f..8abd149428852 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
@@ -10,6 +10,7 @@
 #include "clang/AST/ASTDiagnostic.h"
 #include "clang/AST/ExternalASTSource.h"
 #include "clang/AST/PrettyPrinter.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Basic/DiagnosticIDs.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/TargetInfo.h"
@@ -582,15 +583,16 @@ ClangExpressionParser::ClangExpressionParser(
 
   if (ClangModulesDeclVendor *decl_vendor =
           target_sp->GetClangModulesDeclVendor()) {
-    ClangPersistentVariables *clang_persistent_vars =
-        llvm::cast<ClangPersistentVariables>(
+    if (auto *clang_persistent_vars = llvm::cast<ClangPersistentVariables>(
             target_sp->GetPersistentExpressionStateForLanguage(
-                lldb::eLanguageTypeC));
-    std::unique_ptr<PPCallbacks> pp_callbacks(new LLDBPreprocessorCallbacks(
-        *decl_vendor, *clang_persistent_vars, m_compiler->getSourceManager()));
-    m_pp_callbacks =
-        static_cast<LLDBPreprocessorCallbacks *>(pp_callbacks.get());
-    m_compiler->getPreprocessor().addPPCallbacks(std::move(pp_callbacks));
+                lldb::eLanguageTypeC))) {
+      std::unique_ptr<PPCallbacks> pp_callbacks(
+          new LLDBPreprocessorCallbacks(*decl_vendor, *clang_persistent_vars,
+                                        m_compiler->getSourceManager()));
+      m_pp_callbacks =
+          static_cast<LLDBPreprocessorCallbacks *>(pp_callbacks.get());
+      m_compiler->getPreprocessor().addPPCallbacks(std::move(pp_callbacks));
+    }
   }
 
   // 8. Most of this we get from the CompilerInstance, but we also want to give
@@ -696,10 +698,7 @@ class CodeComplete : public CodeCompleteConsumer {
 
 public:
   /// Constructs a CodeComplete consumer that can be attached to a Sema.
-  /// \param[out] matches
-  ///    The list of matches that the lldb completion API expects as a result.
-  ///    This may already contain matches, so it's only allowed to append
-  ///    to this variable.
+  ///
   /// \param[out] expr
   ///    The whole expression string that we are currently parsing. This
   ///    string needs to be equal to the input the user typed, and NOT the
@@ -976,7 +975,7 @@ ClangExpressionParser::ParseInternal(DiagnosticManager &diagnostic_manager,
   m_compiler->setASTConsumer(std::move(Consumer));
 
   if (ast_context.getLangOpts().Modules) {
-    m_compiler->createModuleManager();
+    m_compiler->createASTReader();
     m_ast_context->setSema(&m_compiler->getSema());
   }
 
@@ -999,7 +998,7 @@ ClangExpressionParser::ParseInternal(DiagnosticManager &diagnostic_manager,
     } else {
       ast_context.setExternalSource(ast_source);
     }
-    decl_map->InstallASTContext(ast_context, m_compiler->getFileManager());
+    decl_map->InstallASTContext(*m_ast_context);
   }
 
   // Check that the ASTReader is properly attached to ASTContext and Sema.
@@ -1036,15 +1035,6 @@ ClangExpressionParser::ParseInternal(DiagnosticManager &diagnostic_manager,
   }
 
   if (!num_errors) {
-    if (type_system_helper->DeclMap() &&
-        !type_system_helper->DeclMap()->ResolveUnknownTypes()) {
-      diagnostic_manager.Printf(eDiagnosticSeverityError,
-                                "Couldn't infer the type of a variable");
-      num_errors++;
-    }
-  }
-
-  if (!num_errors) {
     type_system_helper->CommitPersistentDecls();
   }
 
@@ -1268,8 +1258,9 @@ lldb_private::Status ClangExpressionParser::PrepareForExecution(
           interpret_error, interpret_function_calls);
 
       if (!can_interpret && execution_policy == eExecutionPolicyNever) {
-        err.SetErrorStringWithFormat("Can't run the expression locally: %s",
-                                     interpret_error.AsCString());
+        err.SetErrorStringWithFormat(
+            "Can't evaluate the expression without a running target due to: %s",
+            interpret_error.AsCString());
         return err;
       }
     }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
index 79ad5728bf741..4a410cecb94ad 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.h
@@ -42,7 +42,7 @@ public:
   ///
   /// Initializes class variables.
   ///
-  /// \param[in] exe_scope,
+  /// \param[in] exe_scope
   ///     If non-NULL, an execution context scope that can help to
   ///     correctly create an expression with a valid process for
   ///     optional tuning Objective-C runtime support. Can be NULL.
@@ -77,7 +77,7 @@ public:
   /// \return
   ///     The number of errors encountered during parsing.  0 means
   ///     success.
-  unsigned Parse(DiagnosticManager &diagnostic_manager) override;
+  unsigned Parse(DiagnosticManager &diagnostic_manager);
 
   bool RewriteExpression(DiagnosticManager &diagnostic_manager) override;
 
@@ -99,15 +99,6 @@ public:
   /// \param[in] exe_ctx
   ///     The execution context to write the function into.
   ///
-  /// \param[out] evaluated_statically
-  ///     Set to true if the expression could be interpreted statically;
-  ///     untouched otherwise.
-  ///
-  /// \param[out] const_result
-  ///     If the result of the expression is constant, and the
-  ///     expression has no side effects, this is set to the result of the
-  ///     expression.
-  ///
   /// \param[in] execution_policy
   ///     Determines whether the expression must be JIT-compiled, must be
   ///     evaluated statically, or whether this decision may be made
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
index 21cb33402e7f7..7ebb5fee1ec69 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionSourceCode.cpp
@@ -315,12 +315,10 @@ bool ClangExpressionSourceCode::GetText(
       }
     }
 
-    if (ClangModulesDeclVendor *decl_vendor =
-            target->GetClangModulesDeclVendor()) {
-      ClangPersistentVariables *persistent_vars =
-          llvm::cast<ClangPersistentVariables>(
-              target->GetPersistentExpressionStateForLanguage(
-                  lldb::eLanguageTypeC));
+    ClangModulesDeclVendor *decl_vendor = target->GetClangModulesDeclVendor();
+    auto *persistent_vars = llvm::cast<ClangPersistentVariables>(
+        target->GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
+    if (decl_vendor && persistent_vars) {
       const ClangModulesDeclVendor::ModuleVector &hand_imported_modules =
           persistent_vars->GetHandLoadedClangModules();
       ClangModulesDeclVendor::ModuleVector modules_for_macros;
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionVariable.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionVariable.h
index eb7f74f20a20d..0e6de28ee4dfa 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionVariable.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionVariable.h
@@ -74,9 +74,6 @@ public:
 
   /// Finds a variable by NamedDecl in the list.
   ///
-  /// \param[in] name
-  ///     The name of the requested variable.
-  ///
   /// \return
   ///     The variable requested, or NULL if that variable is not in the list.
   static ClangExpressionVariable *
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
index 8fbfa6e47578b..7f7c0a97f5384 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.cpp
@@ -42,6 +42,8 @@
 
 using namespace lldb_private;
 
+char ClangFunctionCaller::ID;
+
 // ClangFunctionCaller constructor
 ClangFunctionCaller::ClangFunctionCaller(ExecutionContextScope &exe_scope,
                                          const CompilerType &return_type,
@@ -186,10 +188,10 @@ ClangFunctionCaller::CompileFunction(lldb::ThreadSP thread_to_use_sp,
   lldb::ProcessSP jit_process_sp(m_jit_process_wp.lock());
   if (jit_process_sp) {
     const bool generate_debug_info = true;
-    m_parser.reset(new ClangExpressionParser(jit_process_sp.get(), *this,
-                                             generate_debug_info));
-
-    num_errors = m_parser->Parse(diagnostic_manager);
+    auto *clang_parser = new ClangExpressionParser(jit_process_sp.get(), *this,
+                                                   generate_debug_info);
+    num_errors = clang_parser->Parse(diagnostic_manager);
+    m_parser.reset(clang_parser);
   } else {
     diagnostic_manager.PutString(eDiagnosticSeverityError,
                                  "no process - unable to inject function");
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
index 24f6f2eb91b3b..150a913152d01 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangFunctionCaller.h
@@ -59,11 +59,6 @@ class ClangExpressionParser;
 class ClangFunctionCaller : public FunctionCaller {
   friend class ASTStructExtractor;
 
-  /// LLVM-style RTTI support.
-  static bool classof(const Expression *E) {
-    return E->getKind() == eKindClangFunctionCaller;
-  }
-
   class ClangFunctionCallerHelper : public ClangExpressionHelper {
   public:
     ClangFunctionCallerHelper(ClangFunctionCaller &owner) : m_owner(owner) {}
@@ -91,18 +86,23 @@ class ClangFunctionCaller : public FunctionCaller {
                                                             ///layout.
   };
 
+  // LLVM RTTI support
+  static char ID;
+
 public:
+  bool isA(const void *ClassID) const override {
+    return ClassID == &ID || FunctionCaller::isA(ClassID);
+  }
+  static bool classof(const Expression *obj) { return obj->isA(&ID); }
+
   /// Constructor
   ///
   /// \param[in] exe_scope
   ///     An execution context scope that gets us at least a target and
   ///     process.
   ///
-  /// \param[in] ast_context
-  ///     The AST context to evaluate argument types in.
-  ///
-  /// \param[in] return_qualtype
-  ///     An opaque Clang QualType for the function result.  Should be
+  /// \param[in] return_type
+  ///     A compiler type for the function result.  Should be
   ///     defined in ast_context.
   ///
   /// \param[in] function_address
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
index f3df589d73112..0696c669f2e20 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangModulesDeclVendor.cpp
@@ -80,12 +80,10 @@ public:
                                 Stream &error_stream) override;
 
   uint32_t FindDecls(ConstString name, bool append, uint32_t max_matches,
-                     std::vector<clang::NamedDecl *> &decls) override;
+                     std::vector<CompilerDecl> &decls) override;
 
   void ForEachMacro(const ModuleVector &modules,
                     std::function<bool(const std::string &)> handler) override;
-
-  clang::ExternalASTMerger::ImporterSource GetImporterSource() override;
 private:
   void
   ReportModuleExportsHelper(std::set<ClangModulesDeclVendor::ModuleID> &exports,
@@ -110,7 +108,6 @@ private:
   typedef std::set<ModuleID> ImportedModuleSet;
   ImportedModuleMap m_imported_modules;
   ImportedModuleSet m_user_imported_modules;
-  const clang::ExternalASTMerger::OriginMap m_origin_map;
   // We assume that every ASTContext has an ClangASTContext, so we also store
   // a custom ClangASTContext for our internal ASTContext.
   std::unique_ptr<ClangASTContext> m_ast_context;
@@ -160,7 +157,7 @@ ClangModulesDeclVendorImpl::ClangModulesDeclVendorImpl(
     : m_diagnostics_engine(std::move(diagnostics_engine)),
       m_compiler_invocation(std::move(compiler_invocation)),
       m_compiler_instance(std::move(compiler_instance)),
-      m_parser(std::move(parser)), m_origin_map() {
+      m_parser(std::move(parser)) {
 
   // Initialize our ClangASTContext.
   m_ast_context.reset(new ClangASTContext(m_compiler_instance->getASTContext()));
@@ -359,7 +356,7 @@ bool ClangModulesDeclVendorImpl::AddModulesForCompileUnit(
 uint32_t
 ClangModulesDeclVendorImpl::FindDecls(ConstString name, bool append,
                                       uint32_t max_matches,
-                                      std::vector<clang::NamedDecl *> &decls) {
+                                      std::vector<CompilerDecl> &decls) {
   if (!m_enabled) {
     return 0;
   }
@@ -385,7 +382,7 @@ ClangModulesDeclVendorImpl::FindDecls(ConstString name, bool append,
     if (num_matches >= max_matches)
       return num_matches;
 
-    decls.push_back(named_decl);
+    decls.push_back(CompilerDecl(m_ast_context.get(), named_decl));
     ++num_matches;
   }
 
@@ -569,13 +566,6 @@ ClangModulesDeclVendorImpl::DoGetModule(clang::ModuleIdPath path,
                                          is_inclusion_directive);
 }
 
-clang::ExternalASTMerger::ImporterSource
-ClangModulesDeclVendorImpl::GetImporterSource() {
-  return clang::ExternalASTMerger::ImporterSource(
-      m_compiler_instance->getASTContext(),
-      m_compiler_instance->getFileManager(), m_origin_map);
-}
-
 static const char *ModuleImportBufferName = "LLDBModulesMemoryBuffer";
 
 lldb_private::ClangModulesDeclVendor *
@@ -704,7 +694,7 @@ ClangModulesDeclVendor::Create(Target &target) {
 
   instance->getPreprocessor().enableIncrementalProcessing();
 
-  instance->createModuleManager();
+  instance->createASTReader();
 
   instance->createSema(action->getTranslationUnitKind(), nullptr);
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.cpp
index 24dd705e37b17..41d62a462ab4e 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.cpp
@@ -67,39 +67,35 @@ void ClangPersistentVariables::RemovePersistentVariable(
 llvm::Optional<CompilerType>
 ClangPersistentVariables::GetCompilerTypeFromPersistentDecl(
     ConstString type_name) {
-  CompilerType compiler_type;
-  if (clang::TypeDecl *tdecl = llvm::dyn_cast_or_null<clang::TypeDecl>(
-          GetPersistentDecl(type_name))) {
-    compiler_type.SetCompilerType(
-        ClangASTContext::GetASTContext(&tdecl->getASTContext()),
-        reinterpret_cast<lldb::opaque_compiler_type_t>(
-            const_cast<clang::Type *>(tdecl->getTypeForDecl())));
-    return compiler_type;
+  PersistentDecl p = m_persistent_decls.lookup(type_name.GetCString());
+
+  if (p.m_decl == nullptr)
+    return llvm::None;
+
+  if (clang::TypeDecl *tdecl = llvm::dyn_cast<clang::TypeDecl>(p.m_decl)) {
+    opaque_compiler_type_t t = static_cast<opaque_compiler_type_t>(
+        const_cast<clang::Type *>(tdecl->getTypeForDecl()));
+    return CompilerType(p.m_context, t);
   }
   return llvm::None;
 }
 
 void ClangPersistentVariables::RegisterPersistentDecl(ConstString name,
-                                                      clang::NamedDecl *decl) {
-  m_persistent_decls.insert(
-      std::pair<const char *, clang::NamedDecl *>(name.GetCString(), decl));
+                                                      clang::NamedDecl *decl,
+                                                      ClangASTContext *ctx) {
+  PersistentDecl p = {decl, ctx};
+  m_persistent_decls.insert(std::make_pair(name.GetCString(), p));
 
   if (clang::EnumDecl *enum_decl = llvm::dyn_cast<clang::EnumDecl>(decl)) {
     for (clang::EnumConstantDecl *enumerator_decl : enum_decl->enumerators()) {
-      m_persistent_decls.insert(std::pair<const char *, clang::NamedDecl *>(
-          ConstString(enumerator_decl->getNameAsString()).GetCString(),
-          enumerator_decl));
+      p = {enumerator_decl, ctx};
+      m_persistent_decls.insert(std::make_pair(
+          ConstString(enumerator_decl->getNameAsString()).GetCString(), p));
     }
   }
 }
 
 clang::NamedDecl *
 ClangPersistentVariables::GetPersistentDecl(ConstString name) {
-  PersistentDeclMap::const_iterator i =
-      m_persistent_decls.find(name.GetCString());
-
-  if (i == m_persistent_decls.end())
-    return nullptr;
-  else
-    return i->second;
+  return m_persistent_decls.lookup(name.GetCString()).m_decl;
 }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.h
index 95e6c3ac963de..434196b35fd52 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangPersistentVariables.h
@@ -62,7 +62,8 @@ public:
   llvm::Optional<CompilerType>
   GetCompilerTypeFromPersistentDecl(ConstString type_name) override;
 
-  void RegisterPersistentDecl(ConstString name, clang::NamedDecl *decl);
+  void RegisterPersistentDecl(ConstString name, clang::NamedDecl *decl,
+                              ClangASTContext *ctx);
 
   clang::NamedDecl *GetPersistentDecl(ConstString name);
 
@@ -80,7 +81,14 @@ private:
   // The counter used by GetNextPersistentVariableName
   uint32_t m_next_persistent_variable_id = 0;
 
-  typedef llvm::DenseMap<const char *, clang::NamedDecl *> PersistentDeclMap;
+  struct PersistentDecl {
+    /// The persistent decl.
+    clang::NamedDecl *m_decl = nullptr;
+    /// The ClangASTContext for the ASTContext of m_decl.
+    ClangASTContext *m_context = nullptr;
+  };
+
+  typedef llvm::DenseMap<const char *, PersistentDecl> PersistentDeclMap;
   PersistentDeclMap
       m_persistent_decls; ///< Persistent entities declared by the user.
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
index da1ca785635c9..6698797617a31 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp
@@ -38,10 +38,11 @@
 #include "lldb/Host/HostInfo.h"
 #include "lldb/Symbol/Block.h"
 #include "lldb/Symbol/ClangASTContext.h"
-#include "lldb/Symbol/ClangExternalASTSourceCommon.h"
+#include "lldb/Symbol/ClangASTMetadata.h"
 #include "lldb/Symbol/CompileUnit.h"
 #include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/ObjectFile.h"
+#include "lldb/Symbol/SymbolFile.h"
 #include "lldb/Symbol/SymbolVendor.h"
 #include "lldb/Symbol/Type.h"
 #include "lldb/Symbol/VariableList.h"
@@ -62,13 +63,15 @@
 
 using namespace lldb_private;
 
+char ClangUserExpression::ID;
+
 ClangUserExpression::ClangUserExpression(
     ExecutionContextScope &exe_scope, llvm::StringRef expr,
     llvm::StringRef prefix, lldb::LanguageType language,
     ResultType desired_type, const EvaluateExpressionOptions &options,
     ValueObject *ctx_obj)
     : LLVMUserExpression(exe_scope, expr, prefix, language, desired_type,
-                         options, eKindClangUserExpression),
+                         options),
       m_type_system_helper(*m_target_wp.lock(), options.GetExecutionPolicy() ==
                                                     eExecutionPolicyTopLevel),
       m_result_delegate(exe_scope.CalculateTarget()), m_ctx_obj(ctx_obj) {
@@ -347,11 +350,12 @@ bool ClangUserExpression::SetupPersistentState(DiagnosticManager &diagnostic_man
 static void SetupDeclVendor(ExecutionContext &exe_ctx, Target *target) {
   if (ClangModulesDeclVendor *decl_vendor =
           target->GetClangModulesDeclVendor()) {
+    auto *persistent_state = llvm::cast<ClangPersistentVariables>(
+        target->GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
+    if (!persistent_state)
+      return;
     const ClangModulesDeclVendor::ModuleVector &hand_imported_modules =
-        llvm::cast<ClangPersistentVariables>(
-            target->GetPersistentExpressionStateForLanguage(
-                lldb::eLanguageTypeC))
-            ->GetHandLoadedClangModules();
+        persistent_state->GetHandLoadedClangModules();
     ClangModulesDeclVendor::ModuleVector modules_for_macros;
 
     for (ClangModulesDeclVendor::ModuleID module : hand_imported_modules) {
@@ -476,15 +480,18 @@ CppModuleConfiguration GetModuleConfig(lldb::LanguageType language,
     files.AppendIfUnique(f);
   // We also need to look at external modules in the case of -gmodules as they
   // contain the support files for libc++ and the C library.
-  sc.comp_unit->ForEachExternalModule([&files](lldb::ModuleSP module) {
-    for (std::size_t i = 0; i < module->GetNumCompileUnits(); ++i) {
-      const FileSpecList &support_files =
-          module->GetCompileUnitAtIndex(i)->GetSupportFiles();
-      for (const FileSpec &f : support_files) {
-        files.AppendIfUnique(f);
-      }
-    }
-  });
+  llvm::DenseSet<SymbolFile *> visited_symbol_files;
+  sc.comp_unit->ForEachExternalModule(
+      visited_symbol_files, [&files](Module &module) {
+        for (std::size_t i = 0; i < module.GetNumCompileUnits(); ++i) {
+          const FileSpecList &support_files =
+              module.GetCompileUnitAtIndex(i)->GetSupportFiles();
+          for (const FileSpec &f : support_files) {
+            files.AppendIfUnique(f);
+          }
+        }
+        return false;
+      });
 
   LLDB_LOG(log, "[C++ module config] Found {0} support files to analyze",
            files.GetSize());
@@ -576,7 +583,7 @@ bool ClangUserExpression::Parse(DiagnosticManager &diagnostic_manager,
 
   auto on_exit = llvm::make_scope_exit([this]() { ResetDeclMap(); });
 
-  if (!DeclMap()->WillParse(exe_ctx, m_materializer_up.get())) {
+  if (!DeclMap()->WillParse(exe_ctx, GetMaterializer())) {
     diagnostic_manager.PutString(
         eDiagnosticSeverityError,
         "current process state is unsuitable for expression parsing");
@@ -676,10 +683,12 @@ bool ClangUserExpression::Parse(DiagnosticManager &diagnostic_manager,
       register_execution_unit = true;
     }
 
-    if (register_execution_unit)
-      exe_ctx.GetTargetPtr()
-          ->GetPersistentExpressionStateForLanguage(m_language)
-          ->RegisterExecutionUnit(m_execution_unit_sp);
+    if (register_execution_unit) {
+      if (auto *persistent_state =
+              exe_ctx.GetTargetPtr()->GetPersistentExpressionStateForLanguage(
+                  m_language))
+        persistent_state->RegisterExecutionUnit(m_execution_unit_sp);
+    }
   }
 
   if (generate_debug_info) {
@@ -764,7 +773,7 @@ bool ClangUserExpression::Complete(ExecutionContext &exe_ctx,
 
   auto on_exit = llvm::make_scope_exit([this]() { ResetDeclMap(); });
 
-  if (!DeclMap()->WillParse(exe_ctx, m_materializer_up.get())) {
+  if (!DeclMap()->WillParse(exe_ctx, GetMaterializer())) {
     diagnostic_manager.PutString(
         eDiagnosticSeverityError,
         "current process state is unsuitable for expression parsing");
@@ -887,9 +896,9 @@ void ClangUserExpression::ClangUserExpressionHelper::ResetDeclMap(
     Materializer::PersistentVariableDelegate &delegate,
     bool keep_result_in_memory,
     ValueObject *ctx_obj) {
-  m_expr_decl_map_up.reset(
-      new ClangExpressionDeclMap(keep_result_in_memory, &delegate, exe_ctx,
-                                 ctx_obj));
+  m_expr_decl_map_up.reset(new ClangExpressionDeclMap(
+      keep_result_in_memory, &delegate, exe_ctx.GetTargetSP(),
+      exe_ctx.GetTargetRef().GetClangASTImporter(), ctx_obj));
 }
 
 clang::ASTConsumer *
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
index d94f9cc5e0660..00cbffa7fd6fe 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.h
@@ -38,11 +38,14 @@ namespace lldb_private {
 /// the objects needed to parse and interpret or JIT an expression.  It uses
 /// the Clang parser to produce LLVM IR from the expression.
 class ClangUserExpression : public LLVMUserExpression {
+  // LLVM RTTI support
+  static char ID;
+
 public:
-  /// LLVM-style RTTI support.
-  static bool classof(const Expression *E) {
-    return E->getKind() == eKindClangUserExpression;
+  bool isA(const void *ClassID) const override {
+    return ClassID == &ID || LLVMUserExpression::isA(ClassID);
   }
+  static bool classof(const Expression *obj) { return obj->isA(&ID); }
 
   enum { kDefaultTimeout = 500000u };
 
@@ -93,7 +96,7 @@ public:
   /// \param[in] expr
   ///     The expression to parse.
   ///
-  /// \param[in] expr_prefix
+  /// \param[in] prefix
   ///     If non-NULL, a C string containing translation-unit level
   ///     definitions to be included when the expression is parsed.
   ///
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
index 564c62c6a2c69..199e4898e1184 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.cpp
@@ -31,6 +31,8 @@
 
 using namespace lldb_private;
 
+char ClangUtilityFunction::ID;
+
 /// Constructor
 ///
 /// \param[in] text
@@ -40,7 +42,7 @@ using namespace lldb_private;
 ///     The name of the function, as used in the text.
 ClangUtilityFunction::ClangUtilityFunction(ExecutionContextScope &exe_scope,
                                            const char *text, const char *name)
-    : UtilityFunction(exe_scope, text, name, eKindClangUtilityFunction) {
+    : UtilityFunction(exe_scope, text, name) {
   m_function_text.assign(ClangExpressionSourceCode::g_expression_prefix);
   if (text && text[0])
     m_function_text.append(text);
@@ -157,7 +159,7 @@ bool ClangUtilityFunction::Install(DiagnosticManager &diagnostic_manager,
 
 void ClangUtilityFunction::ClangUtilityFunctionHelper::ResetDeclMap(
     ExecutionContext &exe_ctx, bool keep_result_in_memory) {
-  m_expr_decl_map_up.reset(
-      new ClangExpressionDeclMap(keep_result_in_memory, nullptr, exe_ctx,
-                                 nullptr));
+  m_expr_decl_map_up.reset(new ClangExpressionDeclMap(
+      keep_result_in_memory, nullptr, exe_ctx.GetTargetSP(),
+      exe_ctx.GetTargetRef().GetClangASTImporter(), nullptr));
 }
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
index 70ebb2f3ad8aa..9efaa0254c3e5 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/ClangUtilityFunction.h
@@ -33,11 +33,14 @@ namespace lldb_private {
 /// simply provide a way to push a function into the target for the debugger
 /// to call later on.
 class ClangUtilityFunction : public UtilityFunction {
+  // LLVM RTTI support
+  static char ID;
+
 public:
-  /// LLVM-style RTTI support.
-  static bool classof(const Expression *E) {
-    return E->getKind() == eKindClangUtilityFunction;
+  bool isA(const void *ClassID) const override {
+    return ClassID == &ID || UtilityFunction::isA(ClassID);
   }
+  static bool classof(const Expression *obj) { return obj->isA(&ID); }
 
   class ClangUtilityFunctionHelper : public ClangExpressionHelper {
   public:
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRDynamicChecks.h b/lldb/source/Plugins/ExpressionParser/Clang/IRDynamicChecks.h
index 60c0691b21c18..5b9c8007ab763 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRDynamicChecks.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRDynamicChecks.h
@@ -76,10 +76,6 @@ public:
   ///
   /// \param[in] func_name
   ///     The name of the function to prepare for execution in the target.
-  ///
-  /// \param[in] decl_map
-  ///     The mapping used to look up entities in the target process. In
-  ///     this case, used to find objc_msgSend
   IRDynamicChecks(ClangDynamicCheckerFunctions &checker_functions,
                   const char *func_name = "$__lldb_expr");
 
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
index 4e871f7d6a44c..103a7ee46f356 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.cpp
@@ -355,7 +355,7 @@ bool IRForTarget::CreateResultVariable(llvm::Function &llvm_function) {
 
   ConstantInt *new_constant_int =
       ConstantInt::get(llvm::Type::getInt64Ty(m_module->getContext()),
-                       reinterpret_cast<uint64_t>(result_decl), false);
+                       reinterpret_cast<uintptr_t>(result_decl), false);
 
   llvm::Metadata *values[2];
   values[0] = ConstantAsMetadata::get(new_result_global);
diff --git a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
index 893620f7f8e0a..262e8ee0c06c6 100644
--- a/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
+++ b/lldb/source/Plugins/ExpressionParser/Clang/IRForTarget.h
@@ -71,15 +71,6 @@ public:
   ///     variables) should be resolved.  If not, only external functions
   ///     are resolved.
   ///
-  /// \param[in] execution_policy
-  ///     Determines whether an IR interpreter can be used to statically
-  ///     evaluate the expression.
-  ///
-  /// \param[in] const_result
-  ///     This variable is populated with the statically-computed result
-  ///     of the function, if it has no side-effects and the result can
-  ///     be computed statically.
-  ///
   /// \param[in] execution_unit
   ///     The holder for raw data associated with the expression.
   ///
@@ -105,10 +96,6 @@ public:
   ///     $__lldb_expr, and that function is passed to the passes one by
   ///     one.
   ///
-  /// \param[in] interpreter_error
-  ///     An error.  If the expression fails to be interpreted, this error
-  ///     is set to a reason why.
-  ///
   /// \return
   ///     True on success; false otherwise
   bool runOnModule(llvm::Module &llvm_module) override;
@@ -142,9 +129,6 @@ private:
 
   /// The top-level pass implementation
   ///
-  /// \param[in] llvm_module
-  ///     The module currently being processed.
-  ///
   /// \param[in] llvm_function
   ///     The function currently being processed.
   ///
@@ -184,12 +168,12 @@ private:
   /// Find the NamedDecl corresponding to a Value.  This interface is exposed
   /// for the IR interpreter.
   ///
+  /// \param[in] global_val
+  ///     The global entity to search for
+  ///
   /// \param[in] module
   ///     The module containing metadata to search
   ///
-  /// \param[in] global
-  ///     The global entity to search for
-  ///
   /// \return
   ///     The corresponding variable declaration
 public:
@@ -287,7 +271,7 @@ private:
 
   /// Replace a single old-style class reference
   ///
-  /// \param[in] selector_load
+  /// \param[in] class_load
   ///     The load of the statically-allocated selector.
   ///
   /// \return
@@ -362,7 +346,7 @@ private:
 
   /// Handle all the arguments to a function call
   ///
-  /// \param[in] C
+  /// \param[in] call_inst
   ///     The call instruction.
   ///
   /// \return
@@ -381,8 +365,8 @@ private:
   /// Remove calls to __cxa_atexit, which should never be generated by
   /// expressions.
   ///
-  /// \param[in] call_inst
-  ///     The call instruction.
+  /// \param[in] basic_block
+  ///     The basic block currently being processed.
   ///
   /// \return
   ///     True if the scan was successful; false if some operation
@@ -391,7 +375,7 @@ private:
 
   /// The top-level pass implementation
   ///
-  /// \param[in] basic_block
+  /// \param[in] llvm_function
   ///     The function currently being processed.
   ///
   /// \return
@@ -474,28 +458,9 @@ private:
                             ///pointer (see comments in
                             /// ASTResultSynthesizer::SynthesizeBodyResult)
 
-  llvm::GlobalVariable *m_reloc_placeholder; ///< A placeholder that will be
-                                             ///replaced by a pointer to the
-                                             ///final
-  /// location of the static allocation.
-
-  /// UnfoldConstant operates on a constant [Old] which has just been replaced
-  /// with a value [New].  We assume that new_value has been properly placed
-  /// early in the function, in front of the first instruction in the entry
-  /// basic block [FirstEntryInstruction].
-  ///
-  /// UnfoldConstant reads through the uses of Old and replaces Old in those
-  /// uses with New.  Where those uses are constants, the function generates
-  /// new instructions to compute the result of the new, non-constant
-  /// expression and places them before FirstEntryInstruction.  These
-  /// instructions replace the constant uses, so UnfoldConstant calls itself
-  /// recursively for those.
-  ///
-  /// \param[in] llvm_function
-  ///     The function currently being processed.
-  ///
-  /// \return
-  ///     True on success; false otherwise
+  /// A placeholder that will be replaced by a pointer to the final location of
+  /// the static allocation.
+  llvm::GlobalVariable *m_reloc_placeholder;
 
   class FunctionValueCache {
   public:
@@ -513,6 +478,20 @@ private:
 
   FunctionValueCache m_entry_instruction_finder;
 
+  /// UnfoldConstant operates on a constant [Old] which has just been replaced
+  /// with a value [New].  We assume that new_value has been properly placed
+  /// early in the function, in front of the first instruction in the entry
+  /// basic block [FirstEntryInstruction].
+  ///
+  /// UnfoldConstant reads through the uses of Old and replaces Old in those
+  /// uses with New.  Where those uses are constants, the function generates
+  /// new instructions to compute the result of the new, non-constant
+  /// expression and places them before FirstEntryInstruction.  These
+  /// instructions replace the constant uses, so UnfoldConstant calls itself
+  /// recursively for those.
+  ///
+  /// \return
+  ///     True on success; false otherwise
   static bool UnfoldConstant(llvm::Constant *old_constant,
                              llvm::Function *llvm_function,
                              FunctionValueCache &value_maker,
@@ -522,9 +501,6 @@ private:
   /// Commit the allocation in m_data_allocator and use its final location to
   /// replace m_reloc_placeholder.
   ///
-  /// \param[in] module
-  ///     The module that m_data_allocator resides in
-  ///
   /// \return
   ///     True on success; false otherwise
   bool CompleteDataAllocation();