Java: Add guards logic for SwitchExpr default cases.

Author: aschackmull

java/ql/lib/semmle/code/java/controlflow/internal/GuardsLogic.qll

@@ -57,6 +57,8 @@ predicate implies_v1(Guard g1, boolean b1, Guard g2, boolean b2) {
   or
   g1.(DefaultCase).getSwitch().getAConstCase() = g2 and b1 = true and b2 = false
   or
+  g1.(DefaultCase).getSwitchExpr().getAConstCase() = g2 and b1 = true and b2 = false
+  or
   exists(MethodAccess check, int argIndex | check = g1 |
     conditionCheckArgument(check, argIndex, _) and
     g2 = check.getArgument(argIndex) and

java/ql/test/library-tests/guards12/guard.expected

@@ -1,4 +1,6 @@
+| Test.java:5:7:5:17 | case ... | Test.java:3:20:3:20 | s | Test.java:5:12:5:14 | "c" | true | false | Test.java:7:7:7:16 | default |
 | Test.java:5:7:5:17 | case ... | Test.java:3:20:3:20 | s | Test.java:5:12:5:14 | "c" | true | true | Test.java:5:7:5:17 | case ... |
+| Test.java:6:7:6:17 | case ... | Test.java:3:20:3:20 | s | Test.java:6:12:6:14 | "d" | true | false | Test.java:7:7:7:16 | default |
 | Test.java:6:7:6:17 | case ... | Test.java:3:20:3:20 | s | Test.java:6:12:6:14 | "d" | true | true | Test.java:6:7:6:17 | case ... |
 | Test.java:11:7:11:17 | case ... | Test.java:9:13:9:13 | s | Test.java:11:12:11:14 | "c" | true | false | Test.java:13:7:13:16 | default |
 | Test.java:11:7:11:17 | case ... | Test.java:9:13:9:13 | s | Test.java:11:12:11:14 | "c" | true | true | Test.java:11:7:11:17 | case ... |