C#: Only do it for out parameters.

Author: michaelnebel

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

@@ -511,7 +511,8 @@ module Expressions {
     QualifiedWriteAccessOutRef() {
       exists(AssignableDefinitions::OutRefDefinition def |
         def.getExpr() = this and
-        def.getTargetAccess() instanceof QualifiableExpr
+        def.getTargetAccess() instanceof QualifiableExpr and
+        def.getTargetAccess().isOutArgument()
       )
     }
 
@@ -522,25 +523,26 @@ module Expressions {
       first = this
     }
 
-    private QualifiableExpr getOutRefAccess(int i) {
+    private QualifiableExpr getOutAccess(int i) {
       result =
         rank[i + 1](AssignableDefinitions::OutRefDefinition def |
           def.getExpr() = this and
-          def.getTargetAccess() instanceof QualifiableExpr
+          def.getTargetAccess() instanceof QualifiableExpr and
+          def.getTargetAccess().isOutArgument()
         |
           def order by def.getIndex()
         ).getTargetAccess()
     }
 
-    private QualifiableExpr getLastOutRefAccess() {
+    private QualifiableExpr getLastOutAccess() {
       exists(int last |
-        result = this.getOutRefAccess(last) and
-        not exists(this.getOutRefAccess(last + 1))
+        result = this.getOutAccess(last) and
+        not exists(this.getOutAccess(last + 1))
       )
     }
 
     final override predicate last(AstNode last, Completion c) {
-      last = this.getLastOutRefAccess() and
+      last = this.getLastOutAccess() and
       c.isValidFor(last)
     }
 
@@ -559,13 +561,13 @@ module Expressions {
       or
       // Flow from this element to the first write access.
       pred = this and
-      succ = this.getOutRefAccess(0) and
+      succ = this.getOutAccess(0) and
       c.isValidFor(pred) and
       c instanceof NormalCompletion
       or
       // Flow from one access to the next
-      exists(int i | pred = this.getOutRefAccess(i) |
-        succ = this.getOutRefAccess(i + 1) and
+      exists(int i | pred = this.getOutAccess(i) |
+        succ = this.getOutAccess(i + 1) and
         c.isValidFor(pred) and
         c instanceof NormalCompletion
       )