support when-guards

Author: aschackmull

ruby/ql/lib/codeql/ruby/controlflow/internal/Guards.qll

@@ -11,4 +11,13 @@ predicate guardControlsBlock(CfgNodes::AstCfgNode guard, BasicBlock bb, boolean
     s.getValue() = branch and
     conditionBlock.edgeDominates(bb, s)
   )
+  or
+  exists(BasicBlock whenBlock, ConditionalSuccessor s, ControlFlowNode guardNode, int i |
+    guardNode.isAfter(guard.(CfgNodes::ExprNodes::WhenClauseCfgNode).getAstNode()) and
+    whenBlock.getNode(i) = guardNode and
+    i != 0 and
+    guardNode = any(ControlFlowNode n).getASuccessor(s) and
+    s.getValue() = branch and
+    whenBlock.dominates(bb)
+  )
 }