Reduce dyn_cast<> to isa<> or cast<> where possible. Clang edition.

No functional change intended.

llvm-svn: 234587
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index a12f2b1..800abd1 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -2580,10 +2580,9 @@
     case Decl::ObjCProtocol:
       return Sema::OCK_Protocol;
     case Decl::ObjCCategory:
-      if (dyn_cast<ObjCCategoryDecl>(CurContext)->IsClassExtension())
+      if (cast<ObjCCategoryDecl>(CurContext)->IsClassExtension())
         return Sema::OCK_ClassExtension;
-      else
-        return Sema::OCK_Category;
+      return Sema::OCK_Category;
     case Decl::ObjCImplementation:
       return Sema::OCK_Implementation;
     case Decl::ObjCCategoryImpl: