[Sema] Fix an assertion failure in -Wcompletion-handler

NamedDecl::getName() was being called on a constructor.

clang/lib/Analysis/CalledOnceCheck.cpp

@@ -936,8 +936,9 @@ private:
 
   /// Return true if the only parameter of the function is conventional.
   static bool isOnlyParameterConventional(const FunctionDecl *Function) {
-    return Function->getNumParams() == 1 &&
-           hasConventionalSuffix(Function->getName());
+    IdentifierInfo *II = Function->getIdentifier();
+    return Function->getNumParams() == 1 && II &&
+           hasConventionalSuffix(II->getName());
   }
 
   /// Return true/false if 'swift_async' attribute states that the given

clang/test/SemaObjCXX/warn-called-once.mm

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -verify -fsyntax-only -Wcompletion-handler %s
+
+// expected-no-diagnostics
+
+class HasCtor {
+  HasCtor(void *) {}
+};