Fixup - we only need to handle out parameter writes.

Author: michaelnebel

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

@@ -430,7 +430,7 @@ module Expressions {
       not this instanceof ArrayCreation and
       not this instanceof QualifiedWriteAccess and
       not this instanceof QualifiedAccessorWrite and
-      not this instanceof QualifiedWriteAccessOutRef and
+      not this instanceof QualifiedWriteAccessOutParam and
       not this instanceof NoNodeExpr and
       not this instanceof SwitchExpr and
       not this instanceof SwitchCaseExpr and
@@ -493,9 +493,12 @@ module Expressions {
   }
 
   /**
-   * An expression that writes via an accessor in an out/ref parameter, for example `s = M(out x.Field)`,
+   * An expression that writes via an accessor in an `out` parameter, for example `s = M(out x.Field)`,
    * where `Field` is a field.
    *
+   * Note that `ref` parameters are not included here as they are considered reads before the call.
+   * Ideally, we would model `ref` parameters as both reads and writes, but that is not currently supported.
+   *
    * Accessor writes need special attention, because we need to model that the
    * access is written after the method call.
    *
@@ -505,10 +508,10 @@ module Expressions {
    * x -> call M -> x.Field -> s = M(out x.Field)
    * ```
    */
-  private class QualifiedWriteAccessOutRef extends PostOrderTree instanceof Expr {
+  private class QualifiedWriteAccessOutParam extends PostOrderTree instanceof Expr {
     final override predicate propagatesAbnormal(AstNode child) { child = getExprChild(this, _) }
 
-    QualifiedWriteAccessOutRef() {
+    QualifiedWriteAccessOutParam() {
       exists(AssignableDefinitions::OutRefDefinition def |
         def.getExpr() = this and
         def.getTargetAccess() instanceof QualifiableExpr and