[ExpressionParser] Handle llvm::Expected result

This fixes the unchecked-error assertion at runtime.

  Expected<T> must be checked before access or destruction. Expected<T>
  value was in success state. (Note: Expected<T> values in success mode
  must still be checked prior to being destroyed).

llvm-svn: 366853

Author: JDevlieghere

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp

@@ -204,7 +204,11 @@ class Completer : public clang::RecursiveASTVisitor<Completer> {
   llvm::DenseSet<clang::Decl *> m_completed;
 
   bool ImportAndCheckCompletable(clang::Decl *decl) {
-    (void)m_exporter.Import(decl);
+    llvm::Expected<clang::Decl *> imported_decl = m_exporter.Import(decl);
+    if (!imported_decl) {
+      llvm::consumeError(imported_decl.takeError());
+      return false;
+    }
     if (m_completed.count(decl))
       return false;
     if (!llvm::isa<DeclContext>(decl))
@@ -225,7 +229,11 @@ class Completer : public clang::RecursiveASTVisitor<Completer> {
   void Complete(clang::Decl *decl) {
     m_completed.insert(decl);
     auto *decl_context = llvm::cast<DeclContext>(decl);
-    (void)m_exporter.Import(decl);
+    llvm::Expected<clang::Decl *> imported_decl = m_exporter.Import(decl);
+    if (!imported_decl) {
+      llvm::consumeError(imported_decl.takeError());
+      return;
+    }
     m_exporter.CompleteDecl(decl);
     for (Decl *child : decl_context->decls())
       if (ImportAndCheckCompletable(child))