Java: Improve taint step modeling to use postupdate nodes.

java/ql/test/library-tests/dataflow/taint/A.java

@@ -24,4 +24,52 @@ public class A {
     bInput.read(b2);
     sink(b2);
   }
+
+  void streamWrite(ByteArrayOutputStream baos, byte[] data) {
+    baos.write(data);
+  }
+
+  void test3(ByteArrayOutputStream baos) {
+    streamWrite(baos, taint());
+    sink(baos.toByteArray());
+  }
+
+  static class BaosHolder {
+    ByteArrayOutputStream baos = new ByteArrayOutputStream();
+  }
+
+  void streamWriteHolder(BaosHolder bh, byte[] data) {
+    bh.baos.write(data);
+  }
+
+  void test4(BaosHolder bh) {
+    streamWriteHolder(bh, taint());
+    sink(bh.baos.toByteArray());
+  }
+
+  static class DataHolder {
+    byte[] data = new byte[10];
+  }
+
+  void test5_a(DataHolder dh) {
+    ByteArrayInputStream bais = new ByteArrayInputStream(taint());
+    bais.read(dh.data);
+    test5_b(dh);
+  }
+
+  void test5_b(DataHolder dh) {
+    sink(dh.data);
+  }
+
+  void arrayWrite(byte[] from, byte[] to) {
+    for (int i = 0; i < 10; i++) {
+      to[i] = from[i];
+    }
+  }
+
+  void test6() {
+    byte[] b = new byte[10];
+    arrayWrite(taint(), b);
+    sink(b);
+  }
 }