[ASTImporter] Use llvm::Expected and Error in the importer API

Summary:
This is the final phase of the refactoring towards using llvm::Expected
and llvm::Error in the ASTImporter API.
This involves the following:
- remove old Import functions which returned with a pointer,
- use the Import_New functions (which return with Err or Expected) everywhere
  and handle their return value
- rename Import_New functions to Import
This affects both Clang and LLDB.

Reviewers: shafik, teemperor, aprantl, a_sidorin, balazske, a.sidorin

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits, lldb-commits

Tags: #clang, #lldb

Differential Revision: https://reviews.llvm.org/D61438

llvm-svn: 360760
diff --git a/lldb/source/Symbol/CxxModuleHandler.cpp b/lldb/source/Symbol/CxxModuleHandler.cpp
index 3f97672..68a2aab 100644
--- a/lldb/source/Symbol/CxxModuleHandler.cpp
+++ b/lldb/source/Symbol/CxxModuleHandler.cpp
@@ -9,6 +9,7 @@
 #include "lldb/Symbol/CxxModuleHandler.h"
 
 #include "lldb/Symbol/ClangASTContext.h"
+#include "lldb/Utility/Log.h"
 #include "clang/Sema/Lookup.h"
 #include "llvm/Support/Error.h"
 
@@ -214,13 +215,15 @@
   // Import the foreign template arguments.
   llvm::SmallVector<TemplateArgument, 4> imported_args;
 
+  Log *log = lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS);
+
   // If this logic is changed, also update templateArgsAreSupported.
   for (const TemplateArgument &arg : foreign_args.asArray()) {
     switch (arg.getKind()) {
     case TemplateArgument::Type: {
-      llvm::Expected<QualType> type = m_importer->Import_New(arg.getAsType());
+      llvm::Expected<QualType> type = m_importer->Import(arg.getAsType());
       if (!type) {
-        llvm::consumeError(type.takeError());
+        LLDB_LOG_ERROR(log, type.takeError(), "Couldn't import type: {0}");
         return {};
       }
       imported_args.push_back(TemplateArgument(*type));
@@ -229,9 +232,9 @@
     case TemplateArgument::Integral: {
       llvm::APSInt integral = arg.getAsIntegral();
       llvm::Expected<QualType> type =
-          m_importer->Import_New(arg.getIntegralType());
+          m_importer->Import(arg.getIntegralType());
       if (!type) {
-        llvm::consumeError(type.takeError());
+        LLDB_LOG_ERROR(log, type.takeError(), "Couldn't import type: {0}");
         return {};
       }
       imported_args.push_back(