Prevent at compile time converting from Error::success() to Expected<T>

This would trigger an assertion at runtime otherwise.

Differential Revision: https://reviews.llvm.org/D26482

llvm-svn: 286562
diff --git a/lldb/source/Interpreter/OptionGroupVariable.cpp b/lldb/source/Interpreter/OptionGroupVariable.cpp
index a3150d1..c257506 100644
--- a/lldb/source/Interpreter/OptionGroupVariable.cpp
+++ b/lldb/source/Interpreter/OptionGroupVariable.cpp
@@ -59,13 +59,13 @@
   if (DataVisualization::NamedSummaryFormats::GetSummaryFormat(
           ConstString(str), summary_sp) == false)
     return Error("must specify a valid named summary");
-  return Error::success();
+  return Error();
 }
 
 static Error ValidateSummaryString(const char *str, void *) {
   if (!str || !str[0])
     return Error("must specify a non-empty summary string");
-  return Error::success();
+  return Error();
 }
 
 OptionGroupVariable::OptionGroupVariable(bool show_frame_options)
diff --git a/lldb/source/Interpreter/OptionValueString.cpp b/lldb/source/Interpreter/OptionValueString.cpp
index b5ce38c..e61ead0 100644
--- a/lldb/source/Interpreter/OptionValueString.cpp
+++ b/lldb/source/Interpreter/OptionValueString.cpp
@@ -133,7 +133,7 @@
       return error;
   }
   m_current_value.assign(value);
-  return Error::success();
+  return Error();
 }
 
 Error OptionValueString::AppendToCurrentValue(const char *value) {
@@ -148,5 +148,5 @@
     } else
       m_current_value.append(value);
   }
-  return Error::success();
+  return Error();
 }