re PR c++/86926 (ICE for a recursive generic lambda)

	PR c++/86926
	* g++.dg/cpp1z/constexpr-lambda23.C: New test.

From-SVN: r268080

gcc/testsuite/ChangeLog

+2019-01-18  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/86926
+	* g++.dg/cpp1z/constexpr-lambda23.C: New test.
+
 2019-01-18  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR middle-end/88587

gcc/testsuite/g++.dg/cpp1z/constexpr-lambda23.C

+// PR c++/86926
+// { dg-do compile { target c++17 } }
+
+int
+main()
+{
+    constexpr auto f = [](auto self, auto n) {
+        if(n < 2)
+	  return n;
+        return self(self, n - 1) + self(self, n - 2);
+    };
+
+    constexpr auto fibonacci = [=](auto n) { return f(f, n); };
+
+    static_assert(fibonacci(7) == 13);
+}