Java: Add test for Stream.collect.

java/ql/test/library-tests/dataflow/stream-collect/A.java

@@ -0,0 +1,30 @@
+import java.util.*;
+import java.util.stream.*;
+
+public class A {
+  String source() { return "source"; }
+
+  void sink(Object o) { }
+
+  void m() {
+    String[] xs = new String[] { source() };
+    Stream<String> s = Arrays.stream(xs);
+
+    sink(s.collect(Collectors.maxBy(null)).get()); // $ hasValueFlow
+    sink(s.collect(Collectors.minBy(null)).get()); // $ hasValueFlow
+    sink(s.collect(Collectors.toCollection(null)).iterator().next()); // $ hasValueFlow
+    sink(s.collect(Collectors.toList()).get(0)); // $ hasValueFlow
+    sink(s.collect(Collectors.toSet()).iterator().next()); // $ hasValueFlow
+    sink(s.collect(Collectors.toUnmodifiableList()).get(0)); // $ hasValueFlow
+    sink(s.collect(Collectors.toUnmodifiableSet()).iterator().next()); // $ hasValueFlow
+
+    // we don't attempt to cover weird things like this:
+    sink(s.collect(true ? Collectors.toList() : null).get(0)); // $ MISSING: hasValueFlow
+
+    sink(s.collect(Collectors.joining())); // $ hasTaintFlow
+
+    sink(s.collect(Collectors.groupingBy(null)).get(null).get(0)); // $ hasValueFlow
+    sink(s.collect(Collectors.groupingByConcurrent(null)).get(null).get(0)); // $ hasValueFlow
+    sink(s.collect(Collectors.partitioningBy(null)).get(null).get(0)); // $ hasValueFlow
+  }
+}

java/ql/test/library-tests/dataflow/stream-collect/test.ql

@@ -0,0 +1 @@
+import TestUtilities.InlineFlowTest