diff -r 88502b1cf76f -r 7799a51dbe30 test/langtools/tools/javac/patterns/BindingsExistTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/langtools/tools/javac/patterns/BindingsExistTest.java	Wed Nov 27 09:00:01 2019 +0100
@@ -0,0 +1,30 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8231827
+ * @summary Clashing bindings are reported correctly
+ * @compile/fail/ref=BindingsExistTest.out -XDrawDiagnostics --enable-preview -source ${jdk.version} BindingsExistTest.java
+ */
+public class BindingsExistTest {
+    public void t(Object o1, Object o2) {
+        if (o1 instanceof String k && o2 instanceof Integer k) {}
+
+        if (o1 instanceof String k || o2 instanceof Integer k) {}
+
+        if (!(o1 instanceof String k)) {
+            return ;
+        }
+        if (o1 instanceof Integer k) {}
+
+        String s2 = "";
+        if (o1 instanceof String s2) {}
+
+        if (o1 instanceof String s3) {
+            String s3 = "";
+        }
+
+        if (!(o1 instanceof String s4)) {
+            return ;
+        }
+        String s4 = "";
+    }
+}