VariableBinder.cs source code in C# .NET

                        
Code:
                         / 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / Microsoft / Scripting / Compiler / VariableBinder.cs / 1305376 / VariableBinder.cs
                        

                        
                            /* **************************************************************************** 
 *
 * 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.Collections.Generic; 
using System.Collections.ObjectModel; 
using System.Diagnostics;
using System.Dynamic.Utils; 

#if SILVERLIGHT
using System.Core;
#endif 

namespace System.Linq.Expressions.Compiler { 
    /// 
 
    /// Determines if variables are closed over in nested lambdas and need to
    /// be hoisted. 
    /// 
    internal sealed class VariableBinder : ExpressionVisitor {
        private readonly AnalyzedTree _tree = new AnalyzedTree();
        private readonly Stack _scopes = new Stack(); 
        private readonly Stack _constants = new Stack();
        private bool _inQuote; 
 
        internal static AnalyzedTree Bind(LambdaExpression lambda) {
            var binder = new VariableBinder(); 
            binder.Visit(lambda);
            return binder._tree;
        }
 
        private VariableBinder() {
        } 
 
        protected internal override Expression VisitConstant(ConstantExpression node) {
            // If we're in Quote, we can ignore constants completely 
            if (_inQuote) {
                return node;
            }
 
            // Constants that can be emitted into IL don't need to be stored on
            // the delegate 
            if (ILGen.CanEmitConstant(node.Value, node.Type)) { 
                return node;
            } 

            _constants.Peek().AddReference(node.Value, node.Type);
            return node;
        } 

        protected internal override Expression VisitUnary(UnaryExpression node) { 
            if (node.NodeType == ExpressionType.Quote) { 
                bool savedInQuote = _inQuote;
                _inQuote = true; 
                Visit(node.Operand);
                _inQuote = savedInQuote;
            } else {
                Visit(node.Operand); 
            }
            return node; 
        } 

        protected internal override Expression VisitLambda(Expression node) { 
            _scopes.Push(_tree.Scopes[node] = new CompilerScope(node, true));
            _constants.Push(_tree.Constants[node] = new BoundConstants());
            Visit(MergeScopes(node));
            _constants.Pop(); 
            _scopes.Pop();
            return node; 
        } 

        protected internal override Expression VisitInvocation(InvocationExpression node) { 
            LambdaExpression lambda = node.LambdaOperand;

            // optimization: inline code for literal lambda's directly
            if (lambda != null) { 
                // visit the lambda, but treat it more like a scope
                _scopes.Push(_tree.Scopes[lambda] = new CompilerScope(lambda, false)); 
                Visit(MergeScopes(lambda)); 
                _scopes.Pop();
                // visit the invoke's arguments 
                Visit(node.Arguments);
                return node;
            }
 
            return base.VisitInvocation(node);
        } 
 
        protected internal override Expression VisitBlock(BlockExpression node) {
            if (node.Variables.Count == 0) { 
                Visit(node.Expressions);
                return node;
            }
            _scopes.Push(_tree.Scopes[node] = new CompilerScope(node, false)); 
            Visit(MergeScopes(node));
            _scopes.Pop(); 
            return node; 
        }
 
        protected override CatchBlock VisitCatchBlock(CatchBlock node) {
            if (node.Variable == null) {
                Visit(node.Body);
                return node; 
            }
            _scopes.Push(_tree.Scopes[node] = new CompilerScope(node, false)); 
            Visit(node.Body); 
            _scopes.Pop();
            return node; 
        }

        // If the immediate child is another scope, merge it into this one
        // This is an optimization to save environment allocations and 
        // array accesses.
        private ReadOnlyCollection MergeScopes(Expression node) { 
            ReadOnlyCollection body; 
            var lambda = node as LambdaExpression;
            if (lambda != null) { 
                body = new ReadOnlyCollection(new[] { lambda.Body });
            }  else {
                body = ((BlockExpression)node).Expressions;
            } 

            var currentScope = _scopes.Peek(); 
 
            // A block body is mergeable if the body only contains one single block node containing variables,
            // and the child block has the same type as the parent block. 
            while (body.Count == 1 && body[0].NodeType == ExpressionType.Block) {
                var block = (BlockExpression)body[0];

                if (block.Variables.Count > 0) { 
                    // Make sure none of the variables are shadowed. If any
                    // are, we can't merge it. 
                    foreach (var v in block.Variables) { 
                        if (currentScope.Definitions.ContainsKey(v)) {
                            return body; 
                        }
                    }

                    // Otherwise, merge it 
                    if (currentScope.MergedScopes == null) {
                        currentScope.MergedScopes = new Set