/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Microsoft Public License. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Microsoft Public License, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Microsoft Public License.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Dynamic.Utils;
using System.Runtime.CompilerServices;
#if SILVERLIGHT
using System.Core;
#endif
#if CLR2
namespace Microsoft.Scripting.Ast{
using Microsoft.Scripting.Utils;
#else
namespace System.Linq.Expressions {
#endif
/// <summary>
/// Represents a visitor or rewriter for expression trees.
/// </summary>
/// <remarks>
/// This class is designed to be inherited to create more specialized
/// classes whose functionality requires traversing, examining or copying
/// an expression tree.
/// </remarks>
public abstract class ExpressionVisitor {
/// <summary>
/// Initializes a new instance of <see cref="ExpressionVisitor"/>.
/// </summary>
protected ExpressionVisitor() {
}
/// <summary>
/// Dispatches the expression to one of the more specialized visit methods in this class.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
public virtual Expression Visit(Expression node) {
if (node != null) {
return node.Accept(this);
}
return null;
}
/// <summary>
/// Dispatches the list of expressions to one of the more specialized visit methods in this class.
/// </summary>
/// <param name="nodes">The expressions to visit.</param>
/// <returns>The modified expression list, if any of the elements were modified;
/// otherwise, returns the original expression list.</returns>
public ReadOnlyCollection<Expression> Visit(ReadOnlyCollection<Expression> nodes) {
Expression[] newNodes = null;
for (int i = 0, n = nodes.Count; i < n; i++) {
Expression node = Visit(nodes[i]);
if (newNodes != null) {
newNodes[i] = node;
} else if (!object.ReferenceEquals(node, nodes[i])) {
newNodes = new Expression[n];
for (int j = 0; j < i; j++) {
newNodes[j] = nodes[j];
}
newNodes[i] = node;
}
}
if (newNodes == null) {
return nodes;
}
return new TrueReadOnlyCollection<Expression>(newNodes);
}
internal Expression[] VisitArguments(IArgumentProvider nodes) {
Expression[] newNodes = null;
for (int i = 0, n = nodes.ArgumentCount; i < n; i++) {
Expression curNode = nodes.GetArgument(i);
Expression node = Visit(curNode);
if (newNodes != null) {
newNodes[i] = node;
} else if (!object.ReferenceEquals(node, curNode)) {
newNodes = new Expression[n];
for (int j = 0; j < i; j++) {
newNodes[j] = nodes.GetArgument(j);
}
newNodes[i] = node;
}
}
return newNodes;
}
/// <summary>
/// Visits all nodes in the collection using a specified element visitor.
/// </summary>
/// <typeparam name="T">The type of the nodes.</typeparam>
/// <param name="nodes">The nodes to visit.</param>
/// <param name="elementVisitor">A delegate that visits a single element,
/// optionally replacing it with a new element.</param>
/// <returns>The modified node list, if any of the elements were modified;
/// otherwise, returns the original node list.</returns>
public static ReadOnlyCollection<T> Visit<T>(ReadOnlyCollection<T> nodes, Func<T, T> elementVisitor) {
T[] newNodes = null;
for (int i = 0, n = nodes.Count; i < n; i++) {
T node = elementVisitor(nodes[i]);
if (newNodes != null) {
newNodes[i] = node;
} else if (!object.ReferenceEquals(node, nodes[i])) {
newNodes = new T[n];
for (int j = 0; j < i; j++) {
newNodes[j] = nodes[j];
}
newNodes[i] = node;
}
}
if (newNodes == null) {
return nodes;
}
return new TrueReadOnlyCollection<T>(newNodes);
}
/// <summary>
/// Visits an expression, casting the result back to the original expression type.
/// </summary>
/// <typeparam name="T">The type of the expression.</typeparam>
/// <param name="node">The expression to visit.</param>
/// <param name="callerName">The name of the calling method; used to report to report a better error message.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
/// <exception cref="InvalidOperationException">The visit method for this node returned a different type.</exception>
public T VisitAndConvert<T>(T node, string callerName) where T : Expression {
if (node == null) {
return null;
}
node = Visit(node) as T;
if (node == null) {
throw Error.MustRewriteToSameNode(callerName, typeof(T), callerName);
}
return node;
}
/// <summary>
/// Visits an expression, casting the result back to the original expression type.
/// </summary>
/// <typeparam name="T">The type of the expression.</typeparam>
/// <param name="nodes">The expression to visit.</param>
/// <param name="callerName">The name of the calling method; used to report to report a better error message.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
/// <exception cref="InvalidOperationException">The visit method for this node returned a different type.</exception>
public ReadOnlyCollection<T> VisitAndConvert<T>(ReadOnlyCollection<T> nodes, string callerName) where T : Expression {
T[] newNodes = null;
for (int i = 0, n = nodes.Count; i < n; i++) {
T node = Visit(nodes[i]) as T;
if (node == null) {
throw Error.MustRewriteToSameNode(callerName, typeof(T), callerName);
}
if (newNodes != null) {
newNodes[i] = node;
} else if (!object.ReferenceEquals(node, nodes[i])) {
newNodes = new T[n];
for (int j = 0; j < i; j++) {
newNodes[j] = nodes[j];
}
newNodes[i] = node;
}
}
if (newNodes == null) {
return nodes;
}
return new TrueReadOnlyCollection<T>(newNodes);
}
/// <summary>
/// Visits the children of the <see cref="BinaryExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitBinary(BinaryExpression node) {
// Walk children in evaluation order: left, conversion, right
return ValidateBinary(
node,
node.Update(
Visit(node.Left),
VisitAndConvert(node.Conversion, "VisitBinary"),
Visit(node.Right)
)
);
}
/// <summary>
/// Visits the children of the <see cref="BlockExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitBlock(BlockExpression node) {
int count = node.ExpressionCount;
Expression[] nodes = null;
for (int i = 0; i < count; i++) {
Expression oldNode = node.GetExpression(i);
Expression newNode = Visit(oldNode);
if (oldNode != newNode) {
if (nodes == null) {
nodes = new Expression[count];
}
nodes[i] = newNode;
}
}
var v = VisitAndConvert(node.Variables, "VisitBlock");
if (v == node.Variables && nodes == null) {
return node;
} else {
for (int i = 0; i < count; i++) {
if (nodes[i] == null) {
nodes[i] = node.GetExpression(i);
}
}
}
return node.Rewrite(v, nodes);
}
/// <summary>
/// Visits the children of the <see cref="ConditionalExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitConditional(ConditionalExpression node) {
return node.Update(Visit(node.Test), Visit(node.IfTrue), Visit(node.IfFalse));
}
/// <summary>
/// Visits the <see cref="ConstantExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitConstant(ConstantExpression node) {
return node;
}
/// <summary>
/// Visits the <see cref="DebugInfoExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitDebugInfo(DebugInfoExpression node) {
return node;
}
/// <summary>
/// Visits the children of the <see cref="DynamicExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitDynamic(DynamicExpression node) {
Expression[] a = VisitArguments((IArgumentProvider)node);
if (a == null) {
return node;
}
return node.Rewrite(a);
}
/// <summary>
/// Visits the <see cref="DefaultExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitDefault(DefaultExpression node) {
return node;
}
/// <summary>
/// Visits the children of the extension expression.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
/// <remarks>
/// This can be overridden to visit or rewrite specific extension nodes.
/// If it is not overridden, this method will call <see cref="Expression.VisitChildren" />,
/// which gives the node a chance to walk its children. By default,
/// <see cref="Expression.VisitChildren" /> will try to reduce the node.
/// </remarks>
protected internal virtual Expression VisitExtension(Expression node) {
return node.VisitChildren(this);
}
/// <summary>
/// Visits the children of the <see cref="GotoExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitGoto(GotoExpression node) {
return node.Update(VisitLabelTarget(node.Target), Visit(node.Value));
}
/// <summary>
/// Visits the children of the <see cref="InvocationExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitInvocation(InvocationExpression node) {
Expression e = Visit(node.Expression);
Expression[] a = VisitArguments(node);
if (e == node.Expression && a == null) {
return node;
}
return node.Rewrite(e, a);
}
/// <summary>
/// Visits the <see cref="LabelTarget" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual LabelTarget VisitLabelTarget(LabelTarget node) {
return node;
}
/// <summary>
/// Visits the children of the <see cref="LabelExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitLabel(LabelExpression node) {
return node.Update(VisitLabelTarget(node.Target), Visit(node.DefaultValue));
}
/// <summary>
/// Visits the children of the <see cref="Expression<T>" />.
/// </summary>
/// <typeparam name="T">The type of the delegate.</typeparam>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitLambda<T>(Expression<T> node) {
return node.Update(Visit(node.Body), VisitAndConvert(node.Parameters, "VisitLambda"));
}
/// <summary>
/// Visits the children of the <see cref="LoopExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitLoop(LoopExpression node) {
return node.Update(VisitLabelTarget(node.BreakLabel), VisitLabelTarget(node.ContinueLabel), Visit(node.Body));
}
/// <summary>
/// Visits the children of the <see cref="MemberExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitMember(MemberExpression node) {
return node.Update(Visit(node.Expression));
}
/// <summary>
/// Visits the children of the <see cref="IndexExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitIndex(IndexExpression node) {
Expression o = Visit(node.Object);
Expression[] a = VisitArguments(node);
if (o == node.Object && a == null) {
return node;
}
return node.Rewrite(o, a);
}
/// <summary>
/// Visits the children of the <see cref="MethodCallExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitMethodCall(MethodCallExpression node) {
Expression o = Visit(node.Object);
Expression[] a = VisitArguments((IArgumentProvider)node);
if (o == node.Object && a == null) {
return node;
}
return node.Rewrite(o, a);
}
/// <summary>
/// Visits the children of the <see cref="NewArrayExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitNewArray(NewArrayExpression node) {
return node.Update(Visit(node.Expressions));
}
/// <summary>
/// Visits the children of the <see cref="NewExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
protected internal virtual Expression VisitNew(NewExpression node) {
return node.Update(Visit(node.Arguments));
}
/// <summary>
/// Visits the <see cref="ParameterExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitParameter(ParameterExpression node) {
return node;
}
/// <summary>
/// Visits the children of the <see cref="RuntimeVariablesExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitRuntimeVariables(RuntimeVariablesExpression node) {
return node.Update(VisitAndConvert(node.Variables, "VisitRuntimeVariables"));
}
/// <summary>
/// Visits the children of the <see cref="SwitchCase" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual SwitchCase VisitSwitchCase(SwitchCase node) {
return node.Update(Visit(node.TestValues), Visit(node.Body));
}
/// <summary>
/// Visits the children of the <see cref="SwitchExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitSwitch(SwitchExpression node) {
return ValidateSwitch(
node,
node.Update(
Visit(node.SwitchValue),
Visit(node.Cases, VisitSwitchCase),
Visit(node.DefaultBody)
)
);
}
/// <summary>
/// Visits the children of the <see cref="CatchBlock" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual CatchBlock VisitCatchBlock(CatchBlock node) {
return node.Update(VisitAndConvert(node.Variable, "VisitCatchBlock"), Visit(node.Filter), Visit(node.Body));
}
/// <summary>
/// Visits the children of the <see cref="TryExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitTry(TryExpression node) {
return node.Update(
Visit(node.Body),
Visit(node.Handlers, VisitCatchBlock),
Visit(node.Finally),
Visit(node.Fault)
);
}
/// <summary>
/// Visits the children of the <see cref="TypeBinaryExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitTypeBinary(TypeBinaryExpression node) {
return node.Update(Visit(node.Expression));
}
/// <summary>
/// Visits the children of the <see cref="UnaryExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitUnary(UnaryExpression node) {
return ValidateUnary(node, node.Update(Visit(node.Operand)));
}
/// <summary>
/// Visits the children of the <see cref="MemberInitExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitMemberInit(MemberInitExpression node) {
return node.Update(
VisitAndConvert(node.NewExpression, "VisitMemberInit"),
Visit(node.Bindings, VisitMemberBinding)
);
}
/// <summary>
/// Visits the children of the <see cref="ListInitExpression" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected internal virtual Expression VisitListInit(ListInitExpression node) {
return node.Update(
VisitAndConvert(node.NewExpression, "VisitListInit"),
Visit(node.Initializers, VisitElementInit)
);
}
/// <summary>
/// Visits the children of the <see cref="ElementInit" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual ElementInit VisitElementInit(ElementInit node) {
return node.Update(Visit(node.Arguments));
}
/// <summary>
/// Visits the children of the <see cref="MemberBinding" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual MemberBinding VisitMemberBinding(MemberBinding node) {
switch (node.BindingType) {
case MemberBindingType.Assignment:
return VisitMemberAssignment((MemberAssignment)node);
case MemberBindingType.MemberBinding:
return VisitMemberMemberBinding((MemberMemberBinding)node);
case MemberBindingType.ListBinding:
return VisitMemberListBinding((MemberListBinding)node);
default:
throw Error.UnhandledBindingType(node.BindingType);
}
}
/// <summary>
/// Visits the children of the <see cref="MemberAssignment" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual MemberAssignment VisitMemberAssignment(MemberAssignment node) {
return node.Update(Visit(node.Expression));
}
/// <summary>
/// Visits the children of the <see cref="MemberMemberBinding" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding node) {
return node.Update(Visit(node.Bindings, VisitMemberBinding));
}
/// <summary>
/// Visits the children of the <see cref="MemberListBinding" />.
/// </summary>
/// <param name="node">The expression to visit.</param>
/// <returns>The modified expression, if it or any subexpression was modified;
/// otherwise, returns the original expression.</returns>
protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding node) {
return node.Update(Visit(node.Initializers, VisitElementInit));
}
//
// Prevent some common cases of invalid rewrites.
//
// Essentially, we don't want the rewritten node to be semantically
// bound by the factory, which may do the wrong thing. Instead we
// require derived classes to be explicit about what they want to do if
// types change.
//
private static UnaryExpression ValidateUnary(UnaryExpression before, UnaryExpression after) {
if (before != after && before.Method == null) {
if (after.Method != null) {
throw Error.MustRewriteWithoutMethod(after.Method, "VisitUnary");
}
// rethrow has null operand
if (before.Operand != null && after.Operand != null) {
ValidateChildType(before.Operand.Type, after.Operand.Type, "VisitUnary");
}
}
return after;
}
private static BinaryExpression ValidateBinary(BinaryExpression before, BinaryExpression after) {
if (before != after && before.Method == null) {
if (after.Method != null) {
throw Error.MustRewriteWithoutMethod(after.Method, "VisitBinary");
}
ValidateChildType(before.Left.Type, after.Left.Type, "VisitBinary");
ValidateChildType(before.Right.Type, after.Right.Type, "VisitBinary");
}
return after;
}
// We wouldn't need this if switch didn't infer the method.
private static SwitchExpression ValidateSwitch(SwitchExpression before, SwitchExpression after) {
// If we did not have a method, we don't want to bind to one,
// it might not be the right thing.
if (before.Comparison == null && after.Comparison != null) {
throw Error.MustRewriteWithoutMethod(after.Comparison, "VisitSwitch");
}
return after;
}
// Value types must stay as the same type, otherwise it's now a
// different operation, e.g. adding two doubles vs adding two ints.
private static void ValidateChildType(Type before, Type after, string methodName) {
if (before.IsValueType) {
if (TypeUtils.AreEquivalent(before, after)) {
// types are the same value type
return;
}
} else if (!after.IsValueType) {
// both are reference types
return;
}
// Otherwise, it's an invalid type change.
throw Error.MustRewriteChildToSameType(before, after, methodName);
}
}
}
|