Make ModuleDeclarationTree post-order

ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll

@@ -603,7 +603,7 @@ module Trees {
   private class CharacterTree extends LeafTree, CharacterLiteral { }
 
   private class ClassDeclarationTree extends BodyStmtPostOrderTree, ClassDeclaration {
-    override predicate first(AstNode first) {
+    final override predicate first(AstNode first) {
       this.firstInner(first)
       or
       not exists(this.getAChild(_)) and
@@ -952,12 +952,26 @@ module Trees {
     }
   }
 
-  private class ModuleDeclarationTree extends BodyStmtPreOrderTree, ModuleDeclaration {
+  private class ModuleDeclarationTree extends BodyStmtPostOrderTree, ModuleDeclaration {
+    final override predicate first(AstNode first) {
+      this.firstInner(first)
+      or
+      not exists(this.getAChild(_)) and
+      first = this
+    }
+
+    final override predicate succ(AstNode pred, AstNode succ, Completion c) {
+      BodyStmtPostOrderTree.super.succ(pred, succ, c)
+      or
+      succ = this and
+      this.lastInner(pred, c)
+    }
+
     /** Gets the `i`th child in the body of this block. */
     final override AstNode getBodyChild(int i, boolean rescuable) {
       result = this.getScopeExpr() and i = 0 and rescuable = false
       or
-      result = BodyStmtPreOrderTree.super.getBodyChild(i - count(this.getScopeExpr()), rescuable)
+      result = BodyStmtPostOrderTree.super.getBodyChild(i - count(this.getScopeExpr()), rescuable)
     }
   }
 

ql/test/library-tests/controlflow/graph/Cfg.expected

@@ -1389,7 +1389,7 @@ cfg.rb:
 #-----|  -> ... = ...
 
 #  120| ... = ...
-#-----|  -> M
+#-----|  -> nothing
 
 #  120| swap
 #-----|  -> -> { ... }
@@ -1424,7 +1424,7 @@ cfg.rb:
 #-----|  -> [...]
 
 #  122| M
-#-----|  -> nothing
+#-----|  -> EmptyClass
 
 #  123| ... = ...
 #-----|  -> some
@@ -1529,7 +1529,7 @@ cfg.rb:
 #-----|  -> #{...}
 
 #  130| ... = ...
-#-----|  -> EmptyClass
+#-----|  -> M
 
 #  130| Constant
 #-----|  -> 5