Java: Add proper support for variable capture flow.

java/ql/test/library-tests/dataflow/capture/B.java

@@ -0,0 +1,98 @@
+import java.util.*;
+import java.util.function.*;
+
+public class B {
+  static String source(String label) { return null; }
+
+  static void sink(String s) { }
+
+  static void test1() {
+    List<String> l1 = new ArrayList<>();
+    l1.add(source("L"));
+    List<String> l2 = new ArrayList<>();
+    l1.forEach(e -> l2.add(e));
+    sink(l2.get(0)); // $ hasValueFlow=L
+  }
+
+  String bf1;
+  String bf2;
+
+  void test2() {
+    B other = new B();
+    Consumer<String> f = x -> { this.bf1 = x; bf2 = x; other.bf1 = x; };
+
+    // no flow
+    sink(bf1);
+    sink(this.bf2);
+    sink(other.bf1);
+    sink(other.bf2);
+
+    f.accept(source("T"));
+
+    sink(bf1); // $ MISSING: hasValueFlow=T
+    sink(this.bf2); // $ MISSING: hasValueFlow=T
+    sink(other.bf1); // $ hasValueFlow=T
+    sink(other.bf2);
+  }
+
+  static void convert(Map<String, String> inp, Map<String, String> out) {
+    inp.forEach((key, value) -> { out.put(key, value); });
+  }
+
+  void test3() {
+    HashMap<String,String> m1 = new HashMap<>();
+    HashMap<String,String> m2 = new HashMap<>();
+    m1.put(source("Key"), source("Value"));
+    convert(m1, m2);
+    m2.forEach((k, v) -> {
+      sink(k); // $ hasValueFlow=Key
+      sink(v); // $ hasValueFlow=Value
+    });
+  }
+
+  String elem;
+
+  void testParamIn1() {
+    elem = source("pin.This.elem");
+    testParamIn2(source("pin.Arg"));
+  }
+
+  void testParamIn2(String param) {
+    Runnable r = () -> {
+      sink(elem); // $ MISSING: hasValueFlow=pin.This.elem
+      sink(this.elem); // $ MISSING: hasValueFlow=pin.This.elem
+      sink(param); // $ hasValueFlow=pin.Arg
+    };
+    r.run();
+  }
+
+  void testParamOut1() {
+    B other = new B();
+    testParamOut2(other);
+    sink(elem); // $ MISSING: hasValueFlow=pout.This.elem
+    sink(this.elem); // $ MISSING: hasValueFlow=pout.This.elem
+    sink(other.elem); // $ hasValueFlow=pout.param
+  }
+
+  void testParamOut2(B param) {
+    Runnable r = () -> {
+      this.elem = source("pout.This.elem");
+      param.elem = source("pout.param");
+    };
+    r.run();
+  }
+
+  void testCrossLambda() {
+    B b = new B();
+    Runnable sink1 = () -> { sink(b.elem); };
+    Runnable sink2 = () -> { sink(b.elem); }; // $ hasValueFlow=src
+    Runnable src = () -> { b.elem = source("src"); };
+    doRun(sink1);
+    doRun(src);
+    doRun(sink2);
+  }
+
+  void doRun(Runnable r) {
+    r.run();
+  }
+}