QL: add test for redundant-aggregate

Author: erik-krogh

ql/ql/test/queries/style/RedundantAggregate/Foo.qll

@@ -0,0 +1,17 @@
+bindingset[i]
+predicate foo(int i) {
+  exists(int j | j = i | j = 2) // redundant
+  or
+  exists(Even j | j = i) // redundant
+  or
+  exists(int j |
+    j = i // NOT redundant, inlining into a `forall` is not semantics preserving
+  |
+    forall(int k | k = j | k = 2)
+  )
+}
+
+class Even extends int {
+  bindingset[this]
+  Even() { this % 2 = 0 }
+}

ql/ql/test/queries/style/RedundantAggregate/RedundantAggregate.expected

@@ -0,0 +1,2 @@
+| Foo.qll:3:3:3:31 | Exists | The $@ variable in this aggregate is assigned and used exactly once, and the aggregate is therefore redundant. | Foo.qll:3:10:3:14 | j | j |
+| Foo.qll:5:3:5:24 | Exists | The assignment to $@ in the exists(..) can replaced with an instanceof expression. | Foo.qll:5:10:5:15 | j | j |

ql/ql/test/queries/style/RedundantAggregate/RedundantAggregate.qlref

@@ -0,0 +1 @@
+queries/style/RedundantAggregate.ql