/// <summary>
 /// Visit a parse tree produced by <see cref="Z80TestParser.valueDef"/>.
 /// <para>
 /// The default implementation returns the result of calling <see cref="AbstractParseTreeVisitor{Result}.VisitChildren(IRuleNode)"/>
 /// on <paramref name="context"/>.
 /// </para>
 /// </summary>
 /// <param name="context">The parse tree.</param>
 /// <return>The visitor result.</return>
 public override object VisitValueDef(Z80TestParser.ValueDefContext context)
 {
     return(IsInvalidContext(context)
         ? null
         : new ValueMemberNode(context, (ExpressionNode)VisitExpr(context.expr())));
 }