Merge pull request #7053 from hughbe/clang-warnings

diff --git a/lib/AST/TypeRefinementContext.cpp b/lib/AST/TypeRefinementContext.cpp
index c1eb173..c68b2f5 100644
--- a/lib/AST/TypeRefinementContext.cpp
+++ b/lib/AST/TypeRefinementContext.cpp
@@ -285,6 +285,8 @@
   case Reason::Root:
     return SourceRange();
   }
+
+  llvm_unreachable("Unhandled Reason in switch.");
 }
 
 void TypeRefinementContext::print(raw_ostream &OS, SourceManager &SrcMgr,