The fix for PR c++/90711 also fixed this PR.
gcc/testsuite/ChangeLog:
PR c++/93211
PR c++/90711
* g++.dg/template/koenig11.C: New test.
+2020-04-03 Patrick Palka <ppalka@redhat.com>
+
+ PR c++/93211
+ PR c++/90711
+ * g++.dg/template/koenig11.C: New test.
+
2020-04-03 Andre Vieira <andre.simoesdiasvieira@arm.com>
* gcc.target/arm/mve/intrinsics/mve_vector_float.c: Put -mfpu=auto back.
--- /dev/null
+// PR c++/93211
+// { dg-do compile { target c++11 } }
+
+template<typename T>
+void g(T);
+
+template<typename T, decltype(g(T{})) = 0>
+void f() {}
+
+template<typename T, decltype(::g(T{})) = 0>
+void f() {} // { dg-bogus "redefinition" }