From d9ef9f82e16d3d2cfb2c3c1fdacbb82cfbdc95a8 Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Thu, 5 Mar 2026 14:41:38 +0100
Subject: [PATCH] C#: Make Assignment extend BinaryOperation.

---
 csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll | 6 +++++-
 csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll       | 3 ++-
 csharp/ql/test/library-tests/linq/Linq2.ql            | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll b/csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll
index a5576f023d7..9fa2a93724d 100644
--- a/csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll
+++ b/csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll
@@ -11,7 +11,7 @@ import Expr
  * (`LocalVariableDeclAndInitExpr`), a simple assignment (`AssignExpr`), or
  * an assignment operation (`AssignOperation`).
  */
-class Assignment extends Operation, @assign_expr {
+class Assignment extends BinaryOperation, @assign_expr {
   Assignment() {
     this instanceof LocalVariableDeclExpr
     implies
@@ -20,6 +20,10 @@ class Assignment extends Operation, @assign_expr {
     expr_parent(_, 0, this)
   }
 
+  override Expr getLeftOperand() { result = this.getChild(1) }
+
+  override Expr getRightOperand() { result = this.getChild(0) }
+
   /** Gets the left operand of this assignment. */
   Expr getLValue() { result = this.getChild(1) }
 
diff --git a/csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll b/csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll
index ada01065258..1294cdb7c02 100644
--- a/csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll
+++ b/csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll
@@ -233,7 +233,8 @@ class UnaryOperation extends Operation, @un_op {
  * A binary operation. Either a binary arithmetic operation
  * (`BinaryArithmeticOperation`), a binary bitwise operation
  * (`BinaryBitwiseOperation`), a comparison operation (`ComparisonOperation`),
- * or a binary logical operation (`BinaryLogicalOperation`).
+ * a binary logical operation (`BinaryLogicalOperation`), or an
+ * assignment (`Assignment`).
  */
 class BinaryOperation extends Operation, @bin_op {
   /** Gets the left operand of this binary operation. */
diff --git a/csharp/ql/test/library-tests/linq/Linq2.ql b/csharp/ql/test/library-tests/linq/Linq2.ql
index b3909f88b70..5f1fc3de85b 100644
--- a/csharp/ql/test/library-tests/linq/Linq2.ql
+++ b/csharp/ql/test/library-tests/linq/Linq2.ql
@@ -5,4 +5,5 @@
 import csharp
 
 from BinaryOperation e
+where not e instanceof Assignment
 select e, e.getAnOperand()