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/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index d98a3ee..ba477cd 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -303,7 +303,7 @@
     return Error("as it does not refer to a pointer");
   if (pointee.IsVoidType())
     return Error("as it refers to a pointer to void");
-  return Error::success();
+  return Error();
 }
 
 bool CommandObjectExpression::EvaluateExpression(const char *expr,