C#: Swap left and right child in assignments in the QL library.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/Property.qll

@@ -226,7 +226,7 @@ class Property extends DeclarationWithGetSetAccessors, @property {
    * }
    * ```
    */
-  Expr getInitializer() { result = this.getChildExpr(1).getChildExpr(0) }
+  Expr getInitializer() { result = this.getChildExpr(1).getChildExpr(1) }
 
   /**
    * Holds if this property has an initial value. For example, the initial

csharp/ql/lib/semmle/code/csharp/Variable.qll

@@ -408,7 +408,7 @@ class Field extends Variable, AssignableMember, Attributable, TopLevelExprParent
    * }
    * ```
    */
-  final override Expr getInitializer() { result = this.getChildExpr(0).getChildExpr(0) }
+  final override Expr getInitializer() { result = this.getChildExpr(0).getChildExpr(1) }
 
   /**
    * Holds if this field has an initial value. For example, the initial

csharp/ql/lib/semmle/code/csharp/controlflow/internal/ControlFlowGraphImpl.qll

@@ -442,7 +442,6 @@ module Expressions {
   private AstNode getExprChild0(Expr e, int i) {
     not e instanceof NameOfExpr and
     not e instanceof QualifiableExpr and
-    not e instanceof Assignment and
     not e instanceof AnonymousFunctionExpr and
     result = e.getChild(i)
     or
@@ -453,15 +452,6 @@ module Expressions {
         not qe instanceof ExtensionMethodCall and
         result = qe.getChild(i)
       )
-    or
-    // TODO: This can be fixed if the extracted indexes are fixed.
-    e =
-      any(Assignment a |
-        // The left-hand side of an assignment is evaluated before the right-hand side
-        i = 0 and result = a.getLValue()
-        or
-        i = 1 and result = a.getRValue()
-      )
   }
 
   private AstNode getExprChild(Expr e, int i) {

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

@@ -17,18 +17,14 @@ class Assignment extends BinaryOperation, @assign_expr {
     implies
     // Same as `this.(LocalVariableDeclExpr).hasInitializer()` but avoids
     // negative recursion
-    expr_parent(_, 0, this)
+    expr_parent(_, 1, 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) }
+  Expr getLValue() { result = this.getLeftOperand() }
 
   /** Gets the right operand of this assignment. */
-  Expr getRValue() { result = this.getChild(0) }
+  Expr getRValue() { result = this.getRightOperand() }
 
   /** Gets the variable being assigned to, if any. */
   Variable getTargetVariable() { result.getAnAccess() = this.getLValue() }
@@ -80,16 +76,6 @@ class AssignOperation extends Assignment, OperatorCall, @assign_op_expr {
    */
   deprecated predicate hasExpandedAssignment() { none() }
 
-  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() + " ..." }
 }
 
@@ -222,13 +208,9 @@ class AddOrRemoveEventExpr extends Assignment, @assign_event_expr {
   /** Gets the event targeted by this event assignment. */
   Event getTarget() { result = this.getLValue().getTarget() }
 
-  override EventAccess getLValue() { result = this.getChild(1) }
-
-  override Expr getRValue() { result = this.getChild(0) }
-
-  override EventAccess getLeftOperand() { result = this.getChild(1) }
+  override EventAccess getLValue() { result = this.getChild(0) }
 
-  override Expr getRightOperand() { result = this.getChild(0) }
+  override EventAccess getLeftOperand() { result = this.getChild(0) }
 
   override string toString() { result = "... " + this.getOperator() + " ..." }
 }

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

@@ -154,7 +154,7 @@ class LocalVariableDeclExpr extends Expr, @local_var_decl_expr {
   string getName() { result = this.getVariable().getName() }
 
   /** Gets the initializer expression of this local variable declaration, if any. */
-  Expr getInitializer() { result = this.getChild(0) }
+  Expr getInitializer() { result = this.getChild(1) }
 
   /** Holds if this local variable declaration has an initializer. */
   predicate hasInitializer() { exists(this.getInitializer()) }
@@ -174,7 +174,7 @@ class LocalVariableDeclExpr extends Expr, @local_var_decl_expr {
 
   /** Gets the variable access used in this declaration, if any. */
   LocalVariableAccess getAccess() {
-    result = this.getChild(1) or
+    result = this.getChild(0) or
     result = this // `out` argument
   }