Add test for StmtExpr flow

java/ql/test/kotlin/library-tests/dataflow/stmtexpr/StmtExpr.kt

@@ -0,0 +1,16 @@
+class StmtExpr {
+    fun test() {
+        val t = object : Source {
+            override fun a() {
+            }
+        }
+        sink(t) // $ hasValueFlow
+    }
+
+    fun sink(t : Source) {}
+
+}
+
+interface Source {
+    fun a()
+}

java/ql/test/kotlin/library-tests/dataflow/stmtexpr/test.expected

@@ -0,0 +1 @@
+| StmtExpr.kt:3:17:6:9 | new (...) | StmtExpr.kt:7:14:7:14 | t |

java/ql/test/kotlin/library-tests/dataflow/stmtexpr/test.ql

@@ -0,0 +1,18 @@
+import java
+import semmle.code.java.dataflow.DataFlow
+
+class Conf extends DataFlow::Configuration {
+  Conf() { this = "qltest:exprStmtFlow" }
+
+  override predicate isSource(DataFlow::Node n) {
+    n.asExpr().(ClassInstanceExpr).getType().(RefType).getASupertype*().hasName("Source")
+  }
+
+  override predicate isSink(DataFlow::Node n) {
+    n.asExpr().(Argument).getCall().getCallee().hasName("sink")
+  }
+}
+
+from DataFlow::Node src, DataFlow::Node sink, Conf conf
+where conf.hasFlow(src, sink)
+select src, sink