Switch assert(0/false) llvm_unreachable.

llvm-svn: 140367
diff --git a/clang/lib/Sema/IdentifierResolver.cpp b/clang/lib/Sema/IdentifierResolver.cpp
index 95420a3..a643267 100644
--- a/clang/lib/Sema/IdentifierResolver.cpp
+++ b/clang/lib/Sema/IdentifierResolver.cpp
@@ -73,7 +73,7 @@
     }
   }
 
-  assert(0 && "Didn't find this decl on its identifier's chain!");
+  llvm_unreachable("Didn't find this decl on its identifier's chain!");
 }
 
 bool