--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/cpp0x/Wnarrowing17.C	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,19 @@
+// PR c++/90805 - detect narrowing in case values.
+// { dg-do compile { target c++11 } }
+
+void f(int i, char c, unsigned u)
+{
+  switch (i)
+    {
+    case 2149056512u:; // { dg-error "narrowing conversion of .2149056512. from .unsigned int. to .int." }
+    case (long long int) 1e10:; // { dg-error "narrowing conversion of .10000000000. from .long long int. to .int." }
+    // { dg-warning "overflow in conversion" "overflow" { target *-*-* } .-1 }
+    }
+
+  switch (c)
+    // No narrowing, the adjusted type is int.
+    case 300:; // { dg-warning "exceeds maximum value for type" }
+
+  switch (u)
+    case -42:; // { dg-error "narrowing conversion of .-42. from .int. to .unsigned int." }
+}