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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Xml.Xsl;
namespace System.Xml.Xsl.Qil
{
/// <summary>
/// Base internal class for visitors that replace the graph as they visit it.
/// </summary>
internal abstract class QilReplaceVisitor : QilVisitor
{
protected QilFactory f;
public QilReplaceVisitor(QilFactory f)
{
this.f = f;
}
//-----------------------------------------------
// QilVisitor overrides
//-----------------------------------------------
/// <summary>
/// Visit all children of "parent", replacing each child with a copy of each child.
/// </summary>
protected override QilNode VisitChildren(QilNode parent)
{
XmlQueryType oldParentType = parent.XmlType!;
bool recalcType = false;
// Visit children
for (int i = 0; i < parent.Count; i++)
{
QilNode oldChild = parent[i], newChild;
XmlQueryType? oldChildType = oldChild?.XmlType;
// Visit child
if (IsReference(parent, i))
newChild = VisitReference(oldChild!);
else
newChild = Visit(oldChild!);
// Only replace child and recalculate type if oldChild != newChild or oldChild.XmlType != newChild.XmlType
if ((object?)oldChild != (object)newChild || (newChild != null && (object?)oldChildType != (object?)newChild.XmlType))
{
recalcType = true;
parent[i] = newChild;
}
}
if (recalcType)
RecalculateType(parent, oldParentType);
return parent;
}
//-----------------------------------------------
// QilReplaceVisitor methods
//-----------------------------------------------
/// <summary>
/// Once children have been replaced, the Xml type is recalculated.
/// </summary>
protected virtual void RecalculateType(QilNode node, XmlQueryType oldType)
{
XmlQueryType newType;
newType = QilTypeChecker.Check(node);
// Note the use of AtMost to account for cases when folding of Error nodes in the graph cause
// cardinality to be recalculated.
// For example, (Sequence (TextCtor (Error "error")) (Int32 1)) => (Sequence (Error "error") (Int32 1))
// In this case, cardinality has gone from More to One
Debug.Assert(newType.IsSubtypeOf(XmlQueryTypeFactory.AtMost(oldType, oldType.Cardinality)), "Replace shouldn't relax original type");
node.XmlType = newType;
}
}
}
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