--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/warn/Wsign-conversion-4.C	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,14 @@
+// PR c++/86190
+// { dg-options "-Wsign-conversion -Wsign-compare" }
+
+typedef unsigned long size_t;
+
+struct vector {
+  typedef size_t size_type;
+  size_type size();
+};
+
+bool func(vector vec, int var)
+{
+  return vec.size() < static_cast<size_t>(var); // { dg-bogus "may change" }
+}