--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/lookup/pr94257.C	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,16 @@
+// { dg-do compile { target c++11 } }
+// PR94257 ICE with silly inline nest.
+
+inline namespace B { // { dg-message "namespace B { }" }
+namespace B { }  // { dg-message "namespace B::B { }" }
+}
+
+namespace B { // { dg-error ".namespace B. is ambiguous" }
+}
+
+// But this is fine
+namespace D {
+inline namespace D { }
+}
+namespace D {
+}