C#: Let assign operations be operator calls.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll

@@ -67,7 +67,7 @@ class AssignExpr extends Assignment, @simple_assign_expr {
  * (`AssignArithmeticOperation`), a bitwise assignment operation
  * (`AssignBitwiseOperation`), or an event assignment (`AddOrRemoveEventExpr`).
  */
-class AssignOperation extends Assignment, @assign_op_expr {
+class AssignOperation extends Assignment, OperatorCall, @assign_op_expr {
   override string getOperator() { none() }
 
   /**
@@ -79,7 +79,7 @@ class AssignOperation extends Assignment, @assign_op_expr {
    * If an expanded version exists, then it is used in the control
    * flow graph.
    */
-  AssignExpr getExpandedAssignment() { expr_parent(result, 2, this) }
+  AssignExpr getExpandedAssignment() { none() }
 
   /**
    * Holds if this assignment operation has an expanded version.
@@ -92,6 +92,16 @@ class AssignOperation extends Assignment, @assign_op_expr {
    */
   predicate hasExpandedAssignment() { exists(this.getExpandedAssignment()) }
 
+  override Expr getLeftOperand() { result = this.getChild(0) }
+
+  override Expr getRightOperand() { result = this.getChild(1) }
+
+  /** Gets the left operand of this assignment. */
+  override Expr getLValue() { result = this.getChild(0) }
+
+  /** Gets the right operand of this assignment. */
+  override Expr getRValue() { result = this.getChild(1) }
+
   override string toString() { result = "... " + this.getOperator() + " ..." }
 }
 
@@ -219,8 +229,9 @@ class AssignUnsighedRightShiftExpr extends AssignBitwiseOperation, @assign_urshi
  * removal (`RemoveEventExpr`).
  */
 class AddOrRemoveEventExpr extends AssignOperation, @assign_event_expr {
+  // TODO: We need to handle such cases differently as there is no underlying operatorcall.
   /** Gets the event targeted by this event assignment. */
-  Event getTarget() { result = this.getLValue().getTarget() }
+  Event getTargetEvent() { result = this.getLValue().getTarget() }
 
   override EventAccess getLValue() { result = this.getChild(1) }
 

csharp/ql/lib/semmle/code/csharp/exprs/Call.qll

@@ -493,7 +493,7 @@ class ConstructorInitializer extends Call, @constructor_init_expr {
  * }
  * ```
  */
-class OperatorCall extends Call, LateBindableExpr, @operator_invocation_expr {
+class OperatorCall extends Call, LateBindableExpr, @op_invoke_expr {
   override Operator getTarget() { expr_call(this, result) }
 
   override Operator getARuntimeTarget() { result = Call.super.getARuntimeTarget() }