Use None rather than Optional<T>() where possible.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175705 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index bbf2a98..c8f0372 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -628,7 +628,7 @@
     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
     case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
       // This is a template instantiation, so there is no SFINAE.
-      return Optional<TemplateDeductionInfo *>();
+      return None;
 
     case ActiveTemplateInstantiation::DefaultTemplateArgumentInstantiation:
     case ActiveTemplateInstantiation::PriorTemplateArgumentSubstitution:
@@ -647,7 +647,7 @@
     }
   }
 
-  return Optional<TemplateDeductionInfo *>();
+  return None;
 }
 
 /// \brief Retrieve the depth and index of a parameter pack.