--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if26.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,28 @@
+// PR c++/88752
+// { dg-do compile { target c++17 } }
+
+template <int a> struct b { static constexpr int c = a; };
+class d;
+template <typename> struct e { typedef d f; };
+template <typename g> using h = typename e<g>::f;
+template <typename> constexpr bool i = b<true>::c;
+class d {
+public:
+  using j = float;
+};
+template <typename> void k();
+int main() { k<d>(); }
+template <class l> l m;
+template <class, class r> void n(r o) {
+  [](int) {}(o(m<d>));
+}
+template <typename> void k() {
+  n<int>([](auto inputs) {
+    auto p(inputs);
+    using s = h<decltype(p)>;
+    s q;
+    if constexpr (i<typename s::j>)
+      [&] { return q; }();
+    return 42;
+  });
+}