Add test for typeflow propagation through instanceof and pattern-case

smowton · smowton · commit 43c935024a31 · 2023-11-30T11:24:02.000Z
diff --git a/java/ql/test/library-tests/typeflow/A.java b/java/ql/test/library-tests/typeflow/A.java
@@ -102,4 +102,20 @@ public void m9(Object[] xs, int i) {
       default -> { }
     }
   }
+
+  public void m10(Object o) {
+    String s = "Hello world!";
+    Object o2 = s; // Alas, the type information, it is lost
+
+    if (o2 instanceof CharSequence cs) {
+      // Partially recovered statically, but we should know cs is an alias of o and therefore it's really a string.
+      Object target = cs;
+    }
+
+    // The same applies to a pattern case
+    switch (o2) {
+      case CharSequence cs -> { Object target = cs; }
+      default -> { }
+    }
+  }
 }
diff --git a/java/ql/test/library-tests/typeflow/typeflow.expected b/java/ql/test/library-tests/typeflow/typeflow.expected
@@ -14,5 +14,9 @@
 | A.java:70:23:70:24 | x2 | Integer | false |
 | A.java:92:18:92:18 | n | Integer | false |
 | A.java:100:20:100:20 | n | Integer | false |
+| A.java:110:9:110:10 | o2 | String | false |
+| A.java:112:23:112:24 | cs | String | false |
+| A.java:116:13:116:14 | o2 | String | false |
+| A.java:117:49:117:50 | cs | String | false |
 | UnionTypes.java:45:7:45:7 | x | Inter | false |
 | UnionTypes.java:48:23:48:23 | x | Inter | false |
