[analyzer] Clarify 'uninitialized function argument' messages

Differential Revision: https://reviews.llvm.org/D30341

llvm-svn: 297283
diff --git a/clang/test/Analysis/nullptr.cpp b/clang/test/Analysis/nullptr.cpp
index 0e2296f..229ad7b 100644
--- a/clang/test/Analysis/nullptr.cpp
+++ b/clang/test/Analysis/nullptr.cpp
@@ -107,7 +107,7 @@
 void shouldNotCrash() {
   decltype(nullptr) p;
   if (getSymbol())
-    invokeF(p); // expected-warning{{Function call argument is an uninit}}
+    invokeF(p); // expected-warning{{1st function call argument is an uninit}}
   if (getSymbol())
     invokeF(nullptr);
   if (getSymbol()) {