Return a named error in the result object of an expression with no result

Before we returned an error that was not exposed in the SB API and no useful
error message.  This change returns eExpressionProducedNoResult and an
appropriate error string.

<rdar://problem/44539514>

Differential Revision: https://reviews.llvm.org/D53309

llvm-svn: 344647

lldb/source/Expression/ExpressionSourceCode.cpp

@@ -256,7 +256,7 @@ bool ExpressionSourceCode::GetText(std::string &text,
     }
 
     ConstString object_name;
-    if (Language::LanguageIsCPlusPlus(frame->GetLanguage())) {
+    if (1 /* Language::LanguageIsCPlusPlus(frame->GetLanguage())*/) {
       if (target->GetInjectLocalVariables(&exe_ctx)) {
         lldb::VariableListSP var_list_sp =
             frame->GetInScopeVariableList(false, true);