Ruby: CFG: consistency query to check that Expr nodes are post-order

Author: aibaars

ruby/ql/consistency-queries/CfgConsistency.ql

@@ -1 +1,24 @@
 import codeql.ruby.controlflow.internal.ControlFlowGraphImplShared::Consistency
+import codeql.ruby.AST
+import codeql.ruby.controlflow.internal.ControlFlowGraphImpl
+
+/**
+ * All `Expr` nodes are `PostOrderTree`s
+ */
+query predicate nonPostOrderExprTypes(string cls) {
+  exists(Expr e |
+    e instanceof ControlFlowTree and
+    not exists(e.getDesugared()) and
+    cls = e.getAPrimaryQlClass() and
+    not e instanceof PostOrderTree and
+    not e instanceof LeafTree
+  )
+  or
+  exists(Expr e |
+    e instanceof ControlFlowTree and
+    e = any(AstNode x).getDesugared() and
+    cls = e.getAPrimaryQlClass() and
+    not e instanceof PostOrderTree and
+    not e instanceof LeafTree
+  )
+}