[NFC] Add a llvm_unreachable to silence a warning in SubstObjCTypeArgsVisitor

All cases in the switch are covered. NFC.

llvm-svn: 354233

diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index aca82e2..072b0e4 100644 (file)
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -1184,6 +1184,7 @@ struct SubstObjCTypeArgsVisitor
       return Ctx.getObjCObjectPointerType(resultTy);
       }
     }
+    llvm_unreachable("Unexpected ObjCSubstitutionContext!");
   }
 
   QualType VisitFunctionType(const FunctionType *funcType) {