diff -r 88502b1cf76f -r 7799a51dbe30 test/langtools/tools/javac/patterns/PatternVariablesAreFinal.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/langtools/tools/javac/patterns/PatternVariablesAreFinal.java	Wed Nov 27 09:00:01 2019 +0100
@@ -0,0 +1,16 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8231827
+ * @summary Ensure that in type test patterns, the predicate is not trivially provable false.
+ * @compile/fail/ref=PatternVariablesAreFinal.out -XDrawDiagnostics --enable-preview -source ${jdk.version} PatternVariablesAreFinal.java
+ */
+public class PatternVariablesAreFinal {
+    public static void main(String[] args) {
+        Object o = 32;
+        if (o instanceof String s) {
+            s = "hello again";
+            System.out.println(s);
+        }
+        System.out.println("test complete");
+    }
+}