--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-tracking-const1.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,72 @@
+// PR c++/91264
+// { dg-do compile { target c++14 } }
+
+constexpr void
+mod (int &r)
+{
+  r = 99; // { dg-error "modifying a const object" }
+}
+
+constexpr int
+fn1 ()
+{
+  const int i = 0; // { dg-message "originally declared" }
+  mod (const_cast<int &>(i)); // { dg-message "in .constexpr. expansion of " }
+  return i;
+}
+
+constexpr int i1 = fn1 (); // { dg-message "in .constexpr. expansion of " }
+
+constexpr int
+fn2 ()
+{
+  const int i = 5; // { dg-message "originally declared" }
+  const_cast<int &>(i) = 10; // { dg-error "modifying a const object" }
+  return i;
+}
+
+constexpr int i2 = fn2 (); // { dg-message "in .constexpr. expansion of " }
+
+constexpr int
+fn3 ()
+{
+  const int i = 5; // { dg-message "originally declared" }
+  ++const_cast<int &>(i); // { dg-error "modifying a const object" }
+  return i;
+}
+
+constexpr int i3 = fn3 (); // { dg-message "in .constexpr. expansion of " }
+
+constexpr int
+fn4 ()
+{
+  const int i = 5; // { dg-message "originally declared" }
+  const_cast<int &>(i)--; // { dg-error "modifying a const object" }
+  return i;
+}
+
+constexpr int i4 = fn4 (); // { dg-message "in .constexpr. expansion of " }
+
+constexpr int
+fn5 ()
+{
+  const int i = 5; // { dg-message "originally declared" }
+  const_cast<int &>(i) += 2; // { dg-error "modifying a const object" }
+  return i;
+}
+
+constexpr int i5 = fn5 (); // { dg-message "in .constexpr. expansion of " }
+
+constexpr int
+fn6 ()
+{
+  // This is OK.
+  int i = 3;
+  const int *cip = &i;
+  int *ip = const_cast<int *>(cip);
+  *ip = 4;
+  return i;
+}
+
+constexpr int i6 = fn6 ();
+static_assert(i6 == 4, "");