change cast to dyn_cast because d may not be a FunctionDecl

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78876 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 8a4ae3b..d5d3840 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -437,7 +437,7 @@
     return;
   }
 
-  if (FunctionDecl *FD = cast<FunctionDecl>(d)) {
+  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(d)) {
     if (!FD->getResultType()->isPointerType()) {
       S.Diag(Attr.getLoc(), diag::warn_attribute_malloc_pointer_only);
       return;