unified: Add MemberAccess as union of MemberAccessExpr and UnqualifiedMemberAccess

Author: asgerf

unified/ql/lib/codeql/unified/internal/StaticNameBinding.qll

@@ -755,10 +755,25 @@ predicate unqualifiedMemberAccess(
 }
 
 module Public {
+  /**
+   * An expression that accesses a named member, either with an explicit base (`MemberAccessExpr`)
+   * or with an implicit base (`UnqualifiedMemberAccess`).
+   */
+  abstract private class MemberAccessImpl extends Expr {
+    /** Gets the name of the member being accessed. */
+    abstract string getMemberName();
+  }
+
+  final class MemberAccess = MemberAccessImpl;
+
+  private class MemberAccessExprImpl extends MemberAccessImpl instanceof MemberAccessExpr {
+    override string getMemberName() { result = MemberAccessExpr.super.getMemberName() }
+  }
+
   /**
    * A name node appearing in an unqualified position, referring to a member of an enclosing class.
    */
-  class UnqualifiedMemberAccess extends Identifier {
+  class UnqualifiedMemberAccess extends Identifier, MemberAccessImpl {
     private boolean instanceAccess;
     private NameBinding target;
     private ClassLikeDeclaration accessingClass;
@@ -783,7 +798,7 @@ module Public {
     }
 
     /** Gets the simple name of this identifier, that is, the name of the member being accessed. */
-    string getName() { result = this.getValue() }
+    override string getMemberName() { result = this.getValue() }
   }
 }
 

unified/ql/lib/codeql/unified/internal/dataflow/DataFlowGraph.qll

@@ -92,11 +92,11 @@ predicate step(BuilderNode node1, Step step, BuilderNode node2) {
   or
   exists(UnqualifiedMemberAccess access | access.isInstanceAccess() |
     node1.isLocalVariableRead(access, access.getImplicitQualifierVariable()) and
-    step.readName(access.getName()) and
+    step.readName(access.getMemberName()) and
     node2.isResultValue(access)
     or
     (node1.isIncomingValue(access) or node1.isPostUpdate(access)) and
-    step.storeName(access.getName()) and
+    step.storeName(access.getMemberName()) and
     node2.isLocalVariablePostUpdate(access, access.getImplicitQualifierVariable())
   )
   or