/* ****************************************************************************
*
* 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.
*
*
* ***************************************************************************/
#if !CLR2
using System.Linq.Expressions;
#else
using Microsoft.Scripting.Ast;
#endif
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using Microsoft.Scripting.Utils;
using Microsoft.Scripting.Interpreter;
namespace Microsoft.Scripting.Ast{
/// <summary>
/// Wrapping a tree in this node enables jumps from finally blocks
/// It does this by generating control-flow logic in the tree
///
/// Reducing this node requires a full tree walk of its body
/// (but not nested lambdas)
///
/// WARNING: this node cannot contain jumps across blocks, because it
/// assumes any unknown jumps are jumps to an outer scope.
/// </summary>
public sealed class FinallyFlowControlExpression : Expression, IInstructionProvider {
private readonly Expression _body;
private Expression _reduced;
internal FinallyFlowControlExpression(Expression body) {
_body = body;
}
public override bool CanReduce {
get { return true; }
}
public sealed override Type Type {
get { return Body.Type; }
}
public sealed override ExpressionType NodeType {
get { return ExpressionType.Extension; }
}
public Expression Body {
get { return _body; }
}
public override Expression Reduce() {
if (_reduced == null) {
_reduced = new FlowControlRewriter().Reduce(_body);
}
return _reduced;
}
protected override Expression VisitChildren(ExpressionVisitor visitor) {
Expression b = visitor.Visit(_body);
if (b == _body) {
return this;
}
return new FinallyFlowControlExpression(b);
}
void IInstructionProvider.AddInstructions(LightCompiler compiler) {
// the interpreter deals with jumps out of finally blocks just fine:
compiler.Compile(_body);
}
}
public partial class Utils {
public static Expression FinallyFlowControl(Expression body) {
return new FinallyFlowControlExpression(body);
}
}
}
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