Ruby: Support postupdate notes for assignment expressions.

Author: michaelnebel

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -52,6 +52,8 @@ private CfgNodes::ExprCfgNode getALastEvalNode(CfgNodes::ExprCfgNode n) {
   or
   result = n.(CfgNodes::ExprNodes::ConditionalExprCfgNode).getBranch(_)
   or
+  result = n.(CfgNodes::ExprNodes::AssignExprCfgNode).getRhs()
+  or
   exists(CfgNodes::AstCfgNode branch |
     branch = n.(CfgNodes::ExprNodes::CaseExprCfgNode).getBranch(_)
   |
@@ -157,8 +159,6 @@ module LocalFlow {
   predicate localFlowStepCommon(Node nodeFrom, Node nodeTo) {
     localSsaFlowStep(nodeFrom, nodeTo)
     or
-    nodeFrom.asExpr() = nodeTo.asExpr().(CfgNodes::ExprNodes::AssignExprCfgNode).getRhs()
-    or
     nodeFrom.asExpr() = nodeTo.asExpr().(CfgNodes::ExprNodes::BlockArgumentCfgNode).getValue()
     or
     nodeFrom.asExpr() = getALastEvalNode(nodeTo.asExpr())