Java: Extend library support for switch expressions.

java/ql/test/library-tests/dataflow/switchexpr/TestSwitchExpr.java

@@ -0,0 +1,25 @@
+class TestSwitchExpr {
+    Object source() { return new Object(); }
+
+    void sink(Object o) { }
+
+    void test(String s) {
+        Object x1 = source();
+        Object x2 = switch (s) {
+            case "a", "b", ("a" + "b") -> null;
+            default -> x1;
+        };
+        Object x3 = switch (s) {
+            case "c", "d" -> { yield x2; }
+            default -> throw new RuntimeException();
+        };
+        Object x4 = switch (s) {
+            case "a", "b":
+            case "c", "d", ("c" + "d"):
+                yield x3;
+            default:
+                throw new RuntimeException();
+        };
+        sink(x4);
+    }
+}

java/ql/test/library-tests/dataflow/switchexpr/options

@@ -0,0 +1 @@
+//semmle-extractor-options: --javac-args -source 14 -target 14

java/ql/test/library-tests/dataflow/switchexpr/switchexprflow.expected

@@ -0,0 +1,9 @@
+| TestSwitchExpr.java:4:15:4:22 | o |
+| TestSwitchExpr.java:7:21:7:28 | source(...) |
+| TestSwitchExpr.java:8:21:8:30 | switch (...) |
+| TestSwitchExpr.java:10:24:10:25 | x1 |
+| TestSwitchExpr.java:12:21:12:30 | switch (...) |
+| TestSwitchExpr.java:13:38:13:39 | x2 |
+| TestSwitchExpr.java:16:21:16:30 | switch (...) |
+| TestSwitchExpr.java:19:23:19:24 | x3 |
+| TestSwitchExpr.java:23:14:23:15 | x4 |

java/ql/test/library-tests/dataflow/switchexpr/switchexprflow.ql

@@ -0,0 +1,15 @@
+import java
+import semmle.code.java.dataflow.DataFlow
+import DataFlow
+
+class Conf extends Configuration {
+  Conf() { this = "qqconf" }
+
+  override predicate isSource(Node n) { n.asExpr().(MethodAccess).getMethod().hasName("source") }
+
+  override predicate isSink(Node n) { any() }
+}
+
+from Conf c, Node sink
+where c.hasFlow(_, sink)
+select sink