//
// statement.cs: Statement representation for the IL tree.
//
// Authors:
//   Miguel de Icaza (miguel@ximian.com)
//   Martin Baulig (martin@ximian.com)
//   Marek Safar (marek.safar@gmail.com)
//
// Copyright 2001, 2002, 2003 Ximian, Inc.
// Copyright 2003, 2004 Novell, Inc.
// Copyright 2011 Xamarin Inc.
//

using System;
using System.Collections.Generic;

#if STATIC
using IKVM.Reflection.Emit;
#else
using System.Reflection.Emit;
#endif

namespace Mono.CSharp {
	
	public abstract class Statement {
		public Location loc;
		protected bool reachable;

		public bool IsUnreachable {
			get {
				return !reachable;
			}
		}
		
		/// <summary>
		///   Resolves the statement, true means that all sub-statements
		///   did resolve ok.
		///  </summary>
		public virtual bool Resolve (BlockContext bc)
		{
			return true;
		}

		/// <summary>
		///   Return value indicates whether all code paths emitted return.
		/// </summary>
		protected abstract void DoEmit (EmitContext ec);

		public virtual void Emit (EmitContext ec)
		{
			ec.Mark (loc);
			DoEmit (ec);

			if (ec.StatementEpilogue != null) {
				ec.EmitEpilogue ();
			}
		}

		//
		// This routine must be overrided in derived classes and make copies
		// of all the data that might be modified if resolved
		// 
		protected abstract void CloneTo (CloneContext clonectx, Statement target);

		public Statement Clone (CloneContext clonectx)
		{
			Statement s = (Statement) this.MemberwiseClone ();
			CloneTo (clonectx, s);
			return s;
		}

		public virtual Expression CreateExpressionTree (ResolveContext ec)
		{
			ec.Report.Error (834, loc, "A lambda expression with statement body cannot be converted to an expresion tree");
			return null;
		}
		
		public virtual object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		//
		// Return value indicates whether statement has unreachable end
		//
		protected abstract bool DoFlowAnalysis (FlowAnalysisContext fc);

		public bool FlowAnalysis (FlowAnalysisContext fc)
		{
			if (reachable) {
				fc.UnreachableReported = false;
				var res = DoFlowAnalysis (fc);
				return res;
			}

			//
			// Special handling cases
			//
			if (this is Block) {
				return DoFlowAnalysis (fc);
			}

			if (this is EmptyStatement || loc.IsNull)
				return true;

			if (fc.UnreachableReported)
				return true;

			fc.Report.Warning (162, 2, loc, "Unreachable code detected");
			fc.UnreachableReported = true;
			return true;
		}

		public virtual Reachability MarkReachable (Reachability rc)
		{
			if (!rc.IsUnreachable)
				reachable = true;

			return rc;
		}

		protected void CheckExitBoundaries (BlockContext bc, Block scope)
		{
			if (bc.CurrentBlock.ParametersBlock.Original != scope.ParametersBlock.Original) {
				bc.Report.Error (1632, loc, "Control cannot leave the body of an anonymous method");
				return;
			}

			for (var b = bc.CurrentBlock; b != null && b != scope; b = b.Parent) {
				if (b.IsFinallyBlock) {
					Error_FinallyClauseExit (bc);
					break;
				}
			}
		}

		protected void Error_FinallyClauseExit (BlockContext bc)
		{
			bc.Report.Error (157, loc, "Control cannot leave the body of a finally clause");
		}
	}

	public sealed class EmptyStatement : Statement
	{
		public EmptyStatement (Location loc)
		{
			this.loc = loc;
		}

		public override bool Resolve (BlockContext ec)
		{
			return true;
		}

		public override void Emit (EmitContext ec)
		{
		}

		protected override void DoEmit (EmitContext ec)
		{
			throw new NotSupportedException ();
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return false;
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			// nothing needed.
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class If : Statement {
		Expression expr;
		public Statement TrueStatement;
		public Statement FalseStatement;

		bool true_returns, false_returns;

		public If (Expression bool_expr, Statement true_statement, Location l)
			: this (bool_expr, true_statement, null, l)
		{
		}

		public If (Expression bool_expr,
			   Statement true_statement,
			   Statement false_statement,
			   Location l)
		{
			this.expr = bool_expr;
			TrueStatement = true_statement;
			FalseStatement = false_statement;
			loc = l;
		}

		public Expression Expr {
			get {
				return this.expr;
			}
		}
		
		public override bool Resolve (BlockContext ec)
		{
			expr = expr.Resolve (ec);

			var ok = TrueStatement.Resolve (ec);

			if (FalseStatement != null) {
				ok &= FalseStatement.Resolve (ec);
			}

			return ok;
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			Label false_target = ec.DefineLabel ();
			Label end;

			//
			// If we're a boolean constant, Resolve() already
			// eliminated dead code for us.
			//
			Constant c = expr as Constant;
			if (c != null){
				c.EmitSideEffect (ec);

				if (!c.IsDefaultValue)
					TrueStatement.Emit (ec);
				else if (FalseStatement != null)
					FalseStatement.Emit (ec);

				return;
			}			
			
			expr.EmitBranchable (ec, false_target, false);
			
			TrueStatement.Emit (ec);

			if (FalseStatement != null){
				bool branch_emitted = false;
				
				end = ec.DefineLabel ();
				if (!true_returns){
					ec.Emit (OpCodes.Br, end);
					branch_emitted = true;
				}

				ec.MarkLabel (false_target);
				FalseStatement.Emit (ec);

				if (branch_emitted)
					ec.MarkLabel (end);
			} else {
				ec.MarkLabel (false_target);
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			expr.FlowAnalysisConditional (fc);

			var da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);

			fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;

			var res = TrueStatement.FlowAnalysis (fc);

			if (FalseStatement == null) {
				var c = expr as Constant;
				if (c != null && !c.IsDefaultValue)
					return true_returns;

				if (true_returns)
					fc.DefiniteAssignment = da_false;
				else
					fc.DefiniteAssignment &= da_false;
 
				return false;
			}

			if (true_returns) {
				fc.DefiniteAssignment = da_false;
				return FalseStatement.FlowAnalysis (fc);
			}

			var da_true = fc.DefiniteAssignment;

			fc.DefiniteAssignment = da_false;
			res &= FalseStatement.FlowAnalysis (fc);

			if (!TrueStatement.IsUnreachable) {
				if (false_returns || FalseStatement.IsUnreachable)
					fc.DefiniteAssignment = da_true;
				else
					fc.DefiniteAssignment &= da_true;
			}

			return res;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			base.MarkReachable (rc);

			var c = expr as Constant;
			if (c != null) {
				bool take = !c.IsDefaultValue;
				if (take) {
					rc = TrueStatement.MarkReachable (rc);
				} else {
					if (FalseStatement != null)
						rc = FalseStatement.MarkReachable (rc);
				}

				return rc;
			}

			var true_rc = TrueStatement.MarkReachable (rc);
			true_returns = true_rc.IsUnreachable;
	
			if (FalseStatement == null)
				return rc;

			var false_rc = FalseStatement.MarkReachable (rc);
			false_returns = false_rc.IsUnreachable;

			return true_rc & false_rc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			If target = (If) t;

			target.expr = expr.Clone (clonectx);
			target.TrueStatement = TrueStatement.Clone (clonectx);
			if (FalseStatement != null)
				target.FalseStatement = FalseStatement.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Do : LoopStatement
	{
		public Expression expr;
		bool iterator_reachable, end_reachable;

		public Do (Statement statement, BooleanExpression bool_expr, Location doLocation, Location whileLocation)
			: base (statement)
		{
			expr = bool_expr;
			loc = doLocation;
			WhileLocation = whileLocation;
		}

		public Location WhileLocation {
			get; private set;
		}

		public override bool Resolve (BlockContext bc)
		{
			var ok = base.Resolve (bc);

			expr = expr.Resolve (bc);

			return ok;
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			Label loop = ec.DefineLabel ();
			Label old_begin = ec.LoopBegin;
			Label old_end = ec.LoopEnd;
			
			ec.LoopBegin = ec.DefineLabel ();
			ec.LoopEnd = ec.DefineLabel ();
				
			ec.MarkLabel (loop);
			Statement.Emit (ec);
			ec.MarkLabel (ec.LoopBegin);

			// Mark start of while condition
			ec.Mark (WhileLocation);

			//
			// Dead code elimination
			//
			if (expr is Constant) {
				bool res = !((Constant) expr).IsDefaultValue;

				expr.EmitSideEffect (ec);
				if (res)
					ec.Emit (OpCodes.Br, loop);
			} else {
				expr.EmitBranchable (ec, loop, true);
			}
			
			ec.MarkLabel (ec.LoopEnd);

			ec.LoopBegin = old_begin;
			ec.LoopEnd = old_end;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			var res = Statement.FlowAnalysis (fc);

			expr.FlowAnalysisConditional (fc);

			fc.DefiniteAssignment = fc.DefiniteAssignmentOnFalse;

			if (res && !iterator_reachable)
				return !end_reachable;

			if (!end_reachable) {
				var c = expr as Constant;
				if (c != null && !c.IsDefaultValue)
					return true;
			}

			return false;
		}
		
		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			
			var body_rc = Statement.MarkReachable (rc);

			if (body_rc.IsUnreachable && !iterator_reachable) {
				expr = new UnreachableExpression (expr);
				return end_reachable ? rc : Reachability.CreateUnreachable ();
			}

			if (!end_reachable) {
				var c = expr as Constant;
				if (c != null && !c.IsDefaultValue)
					return Reachability.CreateUnreachable ();
			}

			return rc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Do target = (Do) t;

			target.Statement = Statement.Clone (clonectx);
			target.expr = expr.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		public override void SetEndReachable ()
		{
			end_reachable = true;
		}

		public override void SetIteratorReachable ()
		{
			iterator_reachable = true;
		}
	}

	public class While : LoopStatement
	{
		public Expression expr;
		bool empty, infinite, end_reachable;
		List<DefiniteAssignmentBitSet> end_reachable_das;

		public While (BooleanExpression bool_expr, Statement statement, Location l)
			: base (statement)
		{
			this.expr = bool_expr;
			loc = l;
		}

		public override bool Resolve (BlockContext bc)
		{
			bool ok = true;

			expr = expr.Resolve (bc);
			if (expr == null)
				ok = false;

			var c = expr as Constant;
			if (c != null) {
				empty = c.IsDefaultValue;
				infinite = !empty;
			}

			ok &= base.Resolve (bc);
			return ok;
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			if (empty) {
				expr.EmitSideEffect (ec);
				return;
			}

			Label old_begin = ec.LoopBegin;
			Label old_end = ec.LoopEnd;
			
			ec.LoopBegin = ec.DefineLabel ();
			ec.LoopEnd = ec.DefineLabel ();

			//
			// Inform whether we are infinite or not
			//
			if (expr is Constant) {
				// expr is 'true', since the 'empty' case above handles the 'false' case
				ec.MarkLabel (ec.LoopBegin);

				if (ec.EmitAccurateDebugInfo)
					ec.Emit (OpCodes.Nop);

				expr.EmitSideEffect (ec);
				Statement.Emit (ec);
				ec.Emit (OpCodes.Br, ec.LoopBegin);
					
				//
				// Inform that we are infinite (ie, `we return'), only
				// if we do not `break' inside the code.
				//
				ec.MarkLabel (ec.LoopEnd);
			} else {
				Label while_loop = ec.DefineLabel ();

				ec.Emit (OpCodes.Br, ec.LoopBegin);
				ec.MarkLabel (while_loop);

				Statement.Emit (ec);
			
				ec.MarkLabel (ec.LoopBegin);

				ec.Mark (loc);
				expr.EmitBranchable (ec, while_loop, true);
				
				ec.MarkLabel (ec.LoopEnd);
			}	

			ec.LoopBegin = old_begin;
			ec.LoopEnd = old_end;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			expr.FlowAnalysisConditional (fc);

			fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;
			var da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);

			Statement.FlowAnalysis (fc);

			//
			// Special case infinite while with breaks
			//
			if (end_reachable_das != null) {
				da_false = DefiniteAssignmentBitSet.And (end_reachable_das);
				end_reachable_das = null;
			}

			fc.DefiniteAssignment = da_false;

			if (infinite && !end_reachable)
				return true;

			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			base.MarkReachable (rc);

			//
			// Special case unreachable while body
			//
			if (empty) {
				Statement.MarkReachable (Reachability.CreateUnreachable ());
				return rc;
			}

			Statement.MarkReachable (rc);

			//
			// When infinite while end is unreachable via break anything what follows is unreachable too
			//
			if (infinite && !end_reachable)
				return Reachability.CreateUnreachable ();

			return rc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			While target = (While) t;

			target.expr = expr.Clone (clonectx);
			target.Statement = Statement.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
		{
			if (!infinite)
				return;

			if (end_reachable_das == null)
				end_reachable_das = new List<DefiniteAssignmentBitSet> ();

			end_reachable_das.Add (fc.DefiniteAssignment);
		}

		public override void SetEndReachable ()
		{
			end_reachable = true;
		}
	}

	public class For : LoopStatement
	{
		bool infinite, empty, iterator_reachable, end_reachable;
		List<DefiniteAssignmentBitSet> end_reachable_das;
		
		public For (Location l)
			: base (null)
		{
			loc = l;
		}

		public Statement Initializer {
			get; set;
		}

		public Expression Condition {
			get; set;
		}

		public Statement Iterator {
			get; set;
		}

		public override bool Resolve (BlockContext bc)
		{
			Initializer.Resolve (bc);

			if (Condition != null) {
				Condition = Condition.Resolve (bc);
				var condition_constant = Condition as Constant;
				if (condition_constant != null) {
					if (condition_constant.IsDefaultValue) {
						empty = true;
					} else {
						infinite = true;
					}
				}
			} else {
				infinite = true;
			}

			return base.Resolve (bc) && Iterator.Resolve (bc);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			Initializer.FlowAnalysis (fc);

			DefiniteAssignmentBitSet da_false;
			if (Condition != null) {
				Condition.FlowAnalysisConditional (fc);
				fc.DefiniteAssignment = fc.DefiniteAssignmentOnTrue;
				da_false = new DefiniteAssignmentBitSet (fc.DefiniteAssignmentOnFalse);
			} else {
				da_false = fc.BranchDefiniteAssignment ();
			}

			Statement.FlowAnalysis (fc);

			Iterator.FlowAnalysis (fc);

			//
			// Special case infinite for with breaks
			//
			if (end_reachable_das != null) {
				da_false = DefiniteAssignmentBitSet.And (end_reachable_das);
				end_reachable_das = null;
			}

			fc.DefiniteAssignment = da_false;

			if (infinite && !end_reachable)
				return true;

			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			Initializer.MarkReachable (rc);

			var body_rc = Statement.MarkReachable (rc);
			if (!body_rc.IsUnreachable || iterator_reachable) {
				Iterator.MarkReachable (rc);
			}

			//
			// When infinite for end is unreachable via break anything what follows is unreachable too
			//
			if (infinite && !end_reachable) {
				return Reachability.CreateUnreachable ();
			}

			return rc;
		}

		protected override void DoEmit (EmitContext ec)
		{
			if (Initializer != null)
				Initializer.Emit (ec);

			if (empty) {
				Condition.EmitSideEffect (ec);
				return;
			}

			Label old_begin = ec.LoopBegin;
			Label old_end = ec.LoopEnd;
			Label loop = ec.DefineLabel ();
			Label test = ec.DefineLabel ();

			ec.LoopBegin = ec.DefineLabel ();
			ec.LoopEnd = ec.DefineLabel ();

			ec.Emit (OpCodes.Br, test);
			ec.MarkLabel (loop);
			Statement.Emit (ec);

			ec.MarkLabel (ec.LoopBegin);
			Iterator.Emit (ec);

			ec.MarkLabel (test);
			//
			// If test is null, there is no test, and we are just
			// an infinite loop
			//
			if (Condition != null) {
				ec.Mark (Condition.Location);

				//
				// The Resolve code already catches the case for
				// Test == Constant (false) so we know that
				// this is true
				//
				if (Condition is Constant) {
					Condition.EmitSideEffect (ec);
					ec.Emit (OpCodes.Br, loop);
				} else {
					Condition.EmitBranchable (ec, loop, true);
				}
				
			} else
				ec.Emit (OpCodes.Br, loop);
			ec.MarkLabel (ec.LoopEnd);

			ec.LoopBegin = old_begin;
			ec.LoopEnd = old_end;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			For target = (For) t;

			if (Initializer != null)
				target.Initializer = Initializer.Clone (clonectx);
			if (Condition != null)
				target.Condition = Condition.Clone (clonectx);
			if (Iterator != null)
				target.Iterator = Iterator.Clone (clonectx);
			target.Statement = Statement.Clone (clonectx);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
		{
			if (!infinite)
				return;

			if (end_reachable_das == null)
				end_reachable_das = new List<DefiniteAssignmentBitSet> ();

			end_reachable_das.Add (fc.DefiniteAssignment);
		}

		public override void SetEndReachable ()
		{
			end_reachable = true;
		}

		public override void SetIteratorReachable ()
		{
			iterator_reachable = true;
		}
	}

	public abstract class LoopStatement : Statement
	{
		protected LoopStatement (Statement statement)
		{
			Statement = statement;
		}

		public Statement Statement { get; set; }

		public override bool Resolve (BlockContext bc)
		{
			var prev_loop = bc.EnclosingLoop;
			var prev_los = bc.EnclosingLoopOrSwitch;
			bc.EnclosingLoopOrSwitch = bc.EnclosingLoop = this;
			var ok = Statement.Resolve (bc);
			bc.EnclosingLoopOrSwitch = prev_los;
			bc.EnclosingLoop = prev_loop;

			return ok;
		}

		//
		// Needed by possibly infinite loops statements (for, while) and switch statment
		//
		public virtual void AddEndDefiniteAssignment (FlowAnalysisContext fc)
		{
		}

		public virtual void SetEndReachable ()
		{
		}

		public virtual void SetIteratorReachable ()
		{
		}
	}
	
	public class StatementExpression : Statement
	{
		ExpressionStatement expr;
		
		public StatementExpression (ExpressionStatement expr)
		{
			this.expr = expr;
			loc = expr.StartLocation;
		}

		public StatementExpression (ExpressionStatement expr, Location loc)
		{
			this.expr = expr;
			this.loc = loc;
		}

		public ExpressionStatement Expr {
			get {
 				return this.expr;
			}
		}
		
		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			StatementExpression target = (StatementExpression) t;
			target.expr = (ExpressionStatement) expr.Clone (clonectx);
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			expr.EmitStatement (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			expr.FlowAnalysis (fc);
			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			expr.MarkReachable (rc);
			return rc;
		}

		public override bool Resolve (BlockContext ec)
		{
			expr = expr.ResolveStatement (ec);
			return expr != null;
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class StatementErrorExpression : Statement
	{
		Expression expr;

		public StatementErrorExpression (Expression expr)
		{
			this.expr = expr;
			this.loc = expr.StartLocation;
		}

		public Expression Expr {
			get {
				return expr;
			}
		}

		public override bool Resolve (BlockContext bc)
		{
			expr.Error_InvalidExpressionStatement (bc);
			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			throw new NotSupportedException ();
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return false;
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			var t = (StatementErrorExpression) target;

			t.expr = expr.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	//
	// Simple version of statement list not requiring a block
	//
	public class StatementList : Statement
	{
		List<Statement> statements;

		public StatementList (Statement first, Statement second)
		{
			statements = new List<Statement> { first, second };
		}

		#region Properties
		public IList<Statement> Statements {
			get {
				return statements;
			}
		}
		#endregion

		public void Add (Statement statement)
		{
			statements.Add (statement);
		}

		public override bool Resolve (BlockContext ec)
		{
			foreach (var s in statements)
				s.Resolve (ec);

			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			foreach (var s in statements)
				s.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			foreach (var s in statements)
				s.FlowAnalysis (fc);

			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			Reachability res = rc;
			foreach (var s in statements)
				res = s.MarkReachable (rc);

			return res;
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			StatementList t = (StatementList) target;

			t.statements = new List<Statement> (statements.Count);
			foreach (Statement s in statements)
				t.statements.Add (s.Clone (clonectx));
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	//
	// For statements which require special handling when inside try or catch block
	//
	public abstract class ExitStatement : Statement
	{
		protected bool unwind_protect;

		protected abstract bool DoResolve (BlockContext bc);
		protected abstract bool IsLocalExit { get; }

		public override bool Resolve (BlockContext bc)
		{
			var res = DoResolve (bc);

			if (!IsLocalExit) {
				//
				// We are inside finally scope but is it the scope we are exiting
				//
				if (bc.HasSet (ResolveContext.Options.FinallyScope)) {

					for (var b = bc.CurrentBlock; b != null; b = b.Parent) {
						if (b.IsFinallyBlock) {
							Error_FinallyClauseExit (bc);
							break;
						}

						if (b is ParametersBlock)
							break;
					}
				}
			}

			unwind_protect = bc.HasAny (ResolveContext.Options.TryScope | ResolveContext.Options.CatchScope);
			return res;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (IsLocalExit)
				return true;

			if (fc.TryFinally != null) {
			    fc.TryFinally.RegisterForControlExitCheck (new DefiniteAssignmentBitSet (fc.DefiniteAssignment));
			} else {
			    fc.ParametersBlock.CheckControlExit (fc);
			}

			return true;
		}
	}

	/// <summary>
	///   Implements the return statement
	/// </summary>
	public class Return : ExitStatement
	{
		Expression expr;

		public Return (Expression expr, Location l)
		{
			this.expr = expr;
			loc = l;
		}

		#region Properties

		public Expression Expr {
			get {
				return expr;
			}
			protected set {
				expr = value;
			}
		}

		protected override bool IsLocalExit {
			get {
				return false;
			}
		}

		#endregion

		protected override bool DoResolve (BlockContext ec)
		{
			var block_return_type = ec.ReturnType;

			if (expr == null) {
				if (block_return_type.Kind == MemberKind.Void || block_return_type == InternalType.ErrorType)
					return true;

				//
				// Return must not be followed by an expression when
				// the method return type is Task
				//
				if (ec.CurrentAnonymousMethod is AsyncInitializer) {
					var storey = (AsyncTaskStorey) ec.CurrentAnonymousMethod.Storey;
					if (storey.ReturnType == ec.Module.PredefinedTypes.Task.TypeSpec) {
						//
						// Extra trick not to emit ret/leave inside awaiter body
						//
						expr = EmptyExpression.Null;
						return true;
					}

					if (storey.ReturnType.IsGenericTask)
						block_return_type = storey.ReturnType.TypeArguments[0];
				}

				if (ec.CurrentIterator != null) {
					Error_ReturnFromIterator (ec);
				} else if (block_return_type != InternalType.ErrorType) {
					ec.Report.Error (126, loc,
						"An object of a type convertible to `{0}' is required for the return statement",
						block_return_type.GetSignatureForError ());
				}

				return false;
			}

			expr = expr.Resolve (ec);

			AnonymousExpression am = ec.CurrentAnonymousMethod;
			if (am == null) {
				if (block_return_type.Kind == MemberKind.Void) {
					ec.Report.Error (127, loc,
						"`{0}': A return keyword must not be followed by any expression when method returns void",
						ec.GetSignatureForError ());

					return false;
				}
			} else {
				if (am.IsIterator) {
					Error_ReturnFromIterator (ec);
					return false;
				}

				var async_block = am as AsyncInitializer;
				if (async_block != null) {
					if (expr != null) {
						var storey = (AsyncTaskStorey) am.Storey;
						var async_type = storey.ReturnType;

						if (async_type == null && async_block.ReturnTypeInference != null) {
							if (expr.Type.Kind == MemberKind.Void && !(this is ContextualReturn))
								ec.Report.Error (4029, loc, "Cannot return an expression of type `void'");
							else
								async_block.ReturnTypeInference.AddCommonTypeBoundAsync (expr.Type);
							return true;
						}

						if (async_type.Kind == MemberKind.Void) {
							ec.Report.Error (8030, loc,
								"Anonymous function or lambda expression converted to a void returning delegate cannot return a value");
							return false;
						}

						if (!async_type.IsGenericTask) {
							if (this is ContextualReturn)
								return true;

							if (async_block.DelegateType != null) {
								ec.Report.Error (8031, loc,
									"Async lambda expression or anonymous method converted to a `Task' cannot return a value. Consider returning `Task<T>'");
							} else {
								ec.Report.Error (1997, loc,
									"`{0}': A return keyword must not be followed by an expression when async method returns `Task'. Consider using `Task<T>' return type",
									ec.GetSignatureForError ());
							}
							return false;
						}

						//
						// The return type is actually Task<T> type argument
						//
						if (expr.Type == async_type && async_type.TypeArguments [0] != ec.Module.PredefinedTypes.Task.TypeSpec) {
							ec.Report.Error (4016, loc,
								"`{0}': The return expression type of async method must be `{1}' rather than `Task<{1}>'",
								ec.GetSignatureForError (), async_type.TypeArguments[0].GetSignatureForError ());
						} else {
							block_return_type = async_type.TypeArguments[0];
						}
					}
				} else {
					if (block_return_type.Kind == MemberKind.Void) {
						ec.Report.Error (8030, loc,
							"Anonymous function or lambda expression converted to a void returning delegate cannot return a value");
						return false;
					}

					var l = am as AnonymousMethodBody;
					if (l != null && expr != null) {
						if (l.ReturnTypeInference != null) {
							l.ReturnTypeInference.AddCommonTypeBound (expr.Type);
							return true;
						}

						//
						// Try to optimize simple lambda. Only when optimizations are enabled not to cause
						// unexpected debugging experience
						//
						if (this is ContextualReturn && !ec.IsInProbingMode && ec.Module.Compiler.Settings.Optimize) {
							l.DirectMethodGroupConversion = expr.CanReduceLambda (l);
						}
					}
				}
			}

			if (expr == null)
				return false;

			if (expr.Type != block_return_type && expr.Type != InternalType.ErrorType) {
				expr = Convert.ImplicitConversionRequired (ec, expr, block_return_type, loc);

				if (expr == null) {
					if (am != null && block_return_type == ec.ReturnType) {
						ec.Report.Error (1662, loc,
							"Cannot convert `{0}' to delegate type `{1}' because some of the return types in the block are not implicitly convertible to the delegate return type",
							am.ContainerType, am.GetSignatureForError ());
					}
					return false;
				}
			}

			return true;			
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			if (expr != null) {

				var async_body = ec.CurrentAnonymousMethod as AsyncInitializer;
				if (async_body != null) {
					var storey = (AsyncTaskStorey)async_body.Storey;
					Label exit_label = async_body.BodyEnd;

					//
					// It's null for await without async
					//
					if (storey.HoistedReturnValue != null) {
						//
						// Special case hoisted return value (happens in try/finally scenario)
						//
						if (ec.TryFinallyUnwind != null) {
							exit_label = TryFinally.EmitRedirectedReturn (ec, async_body);
						}

						var async_return = (IAssignMethod)storey.HoistedReturnValue;
						async_return.EmitAssign (ec, expr, false, false);
						ec.EmitEpilogue ();
					} else {
						expr.Emit (ec);

						if (ec.TryFinallyUnwind != null)
							exit_label = TryFinally.EmitRedirectedReturn (ec, async_body);
					}

					ec.Emit (OpCodes.Leave, exit_label);
					return;
				}

				expr.Emit (ec);
				ec.EmitEpilogue ();

				if (unwind_protect || ec.EmitAccurateDebugInfo)
					ec.Emit (OpCodes.Stloc, ec.TemporaryReturn ());
			}

			if (unwind_protect) {
				ec.Emit (OpCodes.Leave, ec.CreateReturnLabel ());
			} else if (ec.EmitAccurateDebugInfo) {
				ec.Emit (OpCodes.Br, ec.CreateReturnLabel ());
			} else {
				ec.Emit (OpCodes.Ret);
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (expr != null)
				expr.FlowAnalysis (fc);

			base.DoFlowAnalysis (fc);
			return true;
		}

		void Error_ReturnFromIterator (ResolveContext rc)
		{
			rc.Report.Error (1622, loc,
				"Cannot return a value from iterators. Use the yield return statement to return a value, or yield break to end the iteration");
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Reachability.CreateUnreachable ();
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Return target = (Return) t;
			// It's null for simple return;
			if (expr != null)
				target.expr = expr.Clone (clonectx);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Goto : ExitStatement
	{
		string target;
		LabeledStatement label;
		TryFinally try_finally;

		public Goto (string label, Location l)
		{
			loc = l;
			target = label;
		}

		public string Target {
			get { return target; }
		}

		protected override bool IsLocalExit {
			get {
				return true;
			}
		}

		protected override bool DoResolve (BlockContext bc)
		{
			label = bc.CurrentBlock.LookupLabel (target);
			if (label == null) {
				Error_UnknownLabel (bc, target, loc);
				return false;
			}

			try_finally = bc.CurrentTryBlock as TryFinally;

			CheckExitBoundaries (bc, label.Block);

			return true;
		}

		public static void Error_UnknownLabel (BlockContext bc, string label, Location loc)
		{
			bc.Report.Error (159, loc, "The label `{0}:' could not be found within the scope of the goto statement",
				label);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			// Goto to unreachable label
			if (label == null)
				return true;

			if (fc.AddReachedLabel (label))
				return true;

			label.Block.ScanGotoJump (label, fc);
			return true;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			base.MarkReachable (rc);

			if (try_finally != null) {
				if (try_finally.FinallyBlock.HasReachableClosingBrace) {
					label.AddGotoReference (rc);
				} else {
					label = null;
				}
			} else {
				label.AddGotoReference (rc);
			}

			return Reachability.CreateUnreachable ();
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			// Nothing to clone
		}

		protected override void DoEmit (EmitContext ec)
		{
			// This should only happen for goto from try block to unrechable label
			if (label == null)
				return;

			Label l = label.LabelTarget (ec);

			if (ec.TryFinallyUnwind != null && IsLeavingFinally (label.Block)) {
				var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
				l = TryFinally.EmitRedirectedJump (ec, async_body, l, label.Block);
			}

			ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
		}

		bool IsLeavingFinally (Block labelBlock)
		{
			var b = try_finally.Statement as Block;
			while (b != null) {
				if (b == labelBlock)
					return true;

				b = b.Parent;
			}

			return false;
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class LabeledStatement : Statement {
		string name;
		bool defined;
		bool referenced;
		Label label;
		Block block;
		
		public LabeledStatement (string name, Block block, Location l)
		{
			this.name = name;
			this.block = block;
			this.loc = l;
		}

		public Label LabelTarget (EmitContext ec)
		{
			if (defined)
				return label;

			label = ec.DefineLabel ();
			defined = true;
			return label;
		}

		public Block Block {
			get {
				return block;
			}
		}

		public string Name {
			get { return name; }
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			var t = (LabeledStatement) target;

			t.block = clonectx.RemapBlockCopy (block);
		}

		public override bool Resolve (BlockContext bc)
		{
			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			LabelTarget (ec);
			ec.MarkLabel (label);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (!referenced) {
				fc.Report.Warning (164, 2, loc, "This label has not been referenced");
			}

			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			if (referenced)
				rc = new Reachability ();

			return rc;
		}

		public void AddGotoReference (Reachability rc)
		{
			if (referenced)
				return;

			referenced = true;
			MarkReachable (rc);

			block.ScanGotoJump (this);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}
	

	/// <summary>
	///   `goto default' statement
	/// </summary>
	public class GotoDefault : SwitchGoto
	{		
		public GotoDefault (Location l)
			: base (l)
		{
		}

		public override bool Resolve (BlockContext bc)
		{
			if (bc.Switch == null) {
				Error_GotoCaseRequiresSwitchBlock (bc);
				return false;
			}

			bc.Switch.RegisterGotoCase (null, null);
			base.Resolve (bc);

			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, ec.Switch.DefaultLabel.GetILLabel (ec));
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (!rc.IsUnreachable) {
				var label = switch_statement.DefaultLabel;
				if (label.IsUnreachable) {
					label.MarkReachable (rc);
					switch_statement.Block.ScanGotoJump (label);
				}
			}

			return base.MarkReachable (rc);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	/// <summary>
	///   `goto case' statement
	/// </summary>
	public class GotoCase : SwitchGoto
	{
		Expression expr;
		
		public GotoCase (Expression e, Location l)
			: base (l)
		{
			expr = e;
		}

		public Expression Expr {
			get {
 				return expr;
			}
		}

		public SwitchLabel Label { get; set; }

		public override bool Resolve (BlockContext ec)
		{
			if (ec.Switch == null) {
				Error_GotoCaseRequiresSwitchBlock (ec);
				return false;
			}

			Constant c = expr.ResolveLabelConstant (ec);
			if (c == null) {
				return false;
			}

			Constant res;
			if (ec.Switch.IsNullable && c is NullLiteral) {
				res = c;
			} else {
				TypeSpec type = ec.Switch.SwitchType;
				res = c.Reduce (ec, type);
				if (res == null) {
					c.Error_ValueCannotBeConverted (ec, type, true);
					return false;
				}

				if (!Convert.ImplicitStandardConversionExists (c, type))
					ec.Report.Warning (469, 2, loc,
						"The `goto case' value is not implicitly convertible to type `{0}'",
						type.GetSignatureForError ());

			}

			ec.Switch.RegisterGotoCase (this, res);
			base.Resolve (ec);
			expr = res;

			return true;
		}

		protected override void DoEmit (EmitContext ec)
		{
			ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, Label.GetILLabel (ec));
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			GotoCase target = (GotoCase) t;

			target.expr = expr.Clone (clonectx);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (!rc.IsUnreachable) {
				var label = switch_statement.FindLabel ((Constant) expr);
				if (label.IsUnreachable) {
					label.MarkReachable (rc);
					switch_statement.Block.ScanGotoJump (label);
				}
			}

			return base.MarkReachable (rc);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public abstract class SwitchGoto : Statement
	{
		protected bool unwind_protect;
		protected Switch switch_statement;

		protected SwitchGoto (Location loc)
		{
			this.loc = loc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			// Nothing to clone
		}

		public override bool Resolve (BlockContext bc)
		{
			CheckExitBoundaries (bc, bc.Switch.Block);

			unwind_protect = bc.HasAny (ResolveContext.Options.TryScope | ResolveContext.Options.CatchScope);
			switch_statement = bc.Switch;

			return true;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return true;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Reachability.CreateUnreachable ();
		}

		protected void Error_GotoCaseRequiresSwitchBlock (BlockContext bc)
		{
			bc.Report.Error (153, loc, "A goto case is only valid inside a switch statement");
		}
	}
	
	public class Throw : Statement {
		Expression expr;
		
		public Throw (Expression expr, Location l)
		{
			this.expr = expr;
			loc = l;
		}

		public Expression Expr {
			get {
 				return this.expr;
			}
		}

		public override bool Resolve (BlockContext ec)
		{
			if (expr == null) {
				if (!ec.HasSet (ResolveContext.Options.CatchScope)) {
					ec.Report.Error (156, loc, "A throw statement with no arguments is not allowed outside of a catch clause");
				} else if (ec.HasSet (ResolveContext.Options.FinallyScope)) {
					for (var b = ec.CurrentBlock; b != null && !b.IsCatchBlock; b = b.Parent) {
						if (b.IsFinallyBlock) {
							ec.Report.Error (724, loc,
								"A throw statement with no arguments is not allowed inside of a finally clause nested inside of the innermost catch clause");
							break;
						}
					}
				}

				return true;
			}

			expr = expr.Resolve (ec, ResolveFlags.Type | ResolveFlags.VariableOrValue);

			if (expr == null)
				return false;

			var et = ec.BuiltinTypes.Exception;
			if (Convert.ImplicitConversionExists (ec, expr, et))
				expr = Convert.ImplicitConversion (ec, expr, et, loc);
			else
				ec.Report.Error (155, expr.Location, "The type caught or thrown must be derived from System.Exception");

			return true;
		}
			
		protected override void DoEmit (EmitContext ec)
		{
			if (expr == null) {
				var atv = ec.AsyncThrowVariable;
				if (atv != null) {
					if (atv.HoistedVariant != null) {
						atv.HoistedVariant.Emit (ec);
					} else {
						atv.Emit (ec);
					}

					ec.Emit (OpCodes.Throw);
				} else {
					ec.Emit (OpCodes.Rethrow);
				}
			} else {
				expr.Emit (ec);

				ec.Emit (OpCodes.Throw);
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (expr != null)
				expr.FlowAnalysis (fc);

			return true;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Reachability.CreateUnreachable ();
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Throw target = (Throw) t;

			if (expr != null)
				target.expr = expr.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Break : LocalExitStatement
	{		
		public Break (Location l)
			: base (l)
		{
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		protected override void DoEmit (EmitContext ec)
		{
			var l = ec.LoopEnd;

			if (ec.TryFinallyUnwind != null) {
				var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
				l = TryFinally.EmitRedirectedJump (ec, async_body, l, enclosing_loop.Statement as Block);
			}

			ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			enclosing_loop.AddEndDefiniteAssignment (fc);
			return true;
		}

		protected override bool DoResolve (BlockContext bc)
		{
			enclosing_loop = bc.EnclosingLoopOrSwitch;
			return base.DoResolve (bc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			if (!rc.IsUnreachable)
				enclosing_loop.SetEndReachable ();

			return Reachability.CreateUnreachable ();
		}
	}

	public class Continue : LocalExitStatement
	{		
		public Continue (Location l)
			: base (l)
		{
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}


		protected override void DoEmit (EmitContext ec)
		{
			var l = ec.LoopBegin;

			if (ec.TryFinallyUnwind != null) {
				var async_body = (AsyncInitializer) ec.CurrentAnonymousMethod;
				l = TryFinally.EmitRedirectedJump (ec, async_body, l, enclosing_loop.Statement as Block);
			}

			ec.Emit (unwind_protect ? OpCodes.Leave : OpCodes.Br, l);
		}

		protected override bool DoResolve (BlockContext bc)
		{
			enclosing_loop = bc.EnclosingLoop;
			return base.DoResolve (bc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			if (!rc.IsUnreachable)
				enclosing_loop.SetIteratorReachable ();

			return Reachability.CreateUnreachable ();
		}
	}

	public abstract class LocalExitStatement : ExitStatement
	{
		protected LoopStatement enclosing_loop;

		protected LocalExitStatement (Location loc)
		{
			this.loc = loc;
		}

		protected override bool IsLocalExit {
			get {
				return true;
			}
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			// nothing needed.
		}

		protected override bool DoResolve (BlockContext bc)
		{
			if (enclosing_loop == null) {
				bc.Report.Error (139, loc, "No enclosing loop out of which to break or continue");
				return false;
			}

			var block = enclosing_loop.Statement as Block;

			// Don't need to do extra checks for simple statements loops
			if (block != null) {
				CheckExitBoundaries (bc, block);
			}

			return true;
		}
	}

	public interface ILocalVariable
	{
		void Emit (EmitContext ec);
		void EmitAssign (EmitContext ec);
		void EmitAddressOf (EmitContext ec);
	}

	public interface INamedBlockVariable
	{
		Block Block { get; }
		Expression CreateReferenceExpression (ResolveContext rc, Location loc);
		bool IsDeclared { get; }
		bool IsParameter { get; }
		Location Location { get; }
	}

	public class BlockVariableDeclarator
	{
		LocalVariable li;
		Expression initializer;

		public BlockVariableDeclarator (LocalVariable li, Expression initializer)
		{
			if (li.Type != null)
				throw new ArgumentException ("Expected null variable type");

			this.li = li;
			this.initializer = initializer;
		}

		#region Properties

		public LocalVariable Variable {
			get {
				return li;
			}
		}

		public Expression Initializer {
			get {
				return initializer;
			}
			set {
				initializer = value;
			}
		}

		#endregion

		public virtual BlockVariableDeclarator Clone (CloneContext cloneCtx)
		{
			var t = (BlockVariableDeclarator) MemberwiseClone ();
			if (initializer != null)
				t.initializer = initializer.Clone (cloneCtx);

			return t;
		}
	}

	public class BlockVariable : Statement
	{
		Expression initializer;
		protected FullNamedExpression type_expr;
		protected LocalVariable li;
		protected List<BlockVariableDeclarator> declarators;
		TypeSpec type;

		public BlockVariable (FullNamedExpression type, LocalVariable li)
		{
			this.type_expr = type;
			this.li = li;
			this.loc = type_expr.Location;
		}

		protected BlockVariable (LocalVariable li)
		{
			this.li = li;
		}

		#region Properties

		public List<BlockVariableDeclarator> Declarators {
			get {
				return declarators;
			}
		}

		public Expression Initializer {
			get {
				return initializer;
			}
			set {
				initializer = value;
			}
		}

		public FullNamedExpression TypeExpression {
			get {
				return type_expr;
			}
		}

		public LocalVariable Variable {
			get {
				return li;
			}
		}

		#endregion

		public void AddDeclarator (BlockVariableDeclarator decl)
		{
			if (declarators == null)
				declarators = new List<BlockVariableDeclarator> ();

			declarators.Add (decl);
		}

		static void CreateEvaluatorVariable (BlockContext bc, LocalVariable li)
		{
			if (bc.Report.Errors != 0)
				return;

			var container = bc.CurrentMemberDefinition.Parent.PartialContainer;

			Field f = new Field (container, new TypeExpression (li.Type, li.Location), Modifiers.PUBLIC | Modifiers.STATIC,
				new MemberName (li.Name, li.Location), null);

			container.AddField (f);
			f.Define ();

			li.HoistedVariant = new HoistedEvaluatorVariable (f);
			li.SetIsUsed ();
		}

		public override bool Resolve (BlockContext bc)
		{
			return Resolve (bc, true);
		}

		public bool Resolve (BlockContext bc, bool resolveDeclaratorInitializers)
		{
			if (type == null && !li.IsCompilerGenerated) {
				var vexpr = type_expr as VarExpr;

				//
				// C# 3.0 introduced contextual keywords (var) which behaves like a type if type with
				// same name exists or as a keyword when no type was found
				//
				if (vexpr != null && !vexpr.IsPossibleType (bc)) {
					if (bc.Module.Compiler.Settings.Version < LanguageVersion.V_3)
						bc.Report.FeatureIsNotAvailable (bc.Module.Compiler, loc, "implicitly typed local variable");

					if (li.IsFixed) {
						bc.Report.Error (821, loc, "A fixed statement cannot use an implicitly typed local variable");
						return false;
					}

					if (li.IsConstant) {
						bc.Report.Error (822, loc, "An implicitly typed local variable cannot be a constant");
						return false;
					}

					if (Initializer == null) {
						bc.Report.Error (818, loc, "An implicitly typed local variable declarator must include an initializer");
						return false;
					}

					if (declarators != null) {
						bc.Report.Error (819, loc, "An implicitly typed local variable declaration cannot include multiple declarators");
						declarators = null;
					}

					Initializer = Initializer.Resolve (bc);
					if (Initializer != null) {
						((VarExpr) type_expr).InferType (bc, Initializer);
						type = type_expr.Type;
					} else {
						// Set error type to indicate the var was placed correctly but could
						// not be infered
						//
						// var a = missing ();
						//
						type = InternalType.ErrorType;
					}
				}

				if (type == null) {
					type = type_expr.ResolveAsType (bc);
					if (type == null)
						return false;

					if (li.IsConstant && !type.IsConstantCompatible) {
						Const.Error_InvalidConstantType (type, loc, bc.Report);
					}
				}

				if (type.IsStatic)
					FieldBase.Error_VariableOfStaticClass (loc, li.Name, type, bc.Report);

				li.Type = type;
			}

			bool eval_global = bc.Module.Compiler.Settings.StatementMode && bc.CurrentBlock is ToplevelBlock;
			if (eval_global) {
				CreateEvaluatorVariable (bc, li);
			} else if (type != InternalType.ErrorType) {
				li.PrepareAssignmentAnalysis (bc);
			}

			if (initializer != null) {
				initializer = ResolveInitializer (bc, li, initializer);
				// li.Variable.DefinitelyAssigned 
			}

			if (declarators != null) {
				foreach (var d in declarators) {
					d.Variable.Type = li.Type;
					if (eval_global) {
						CreateEvaluatorVariable (bc, d.Variable);
					} else if (type != InternalType.ErrorType) {
						d.Variable.PrepareAssignmentAnalysis (bc);
					}

					if (d.Initializer != null && resolveDeclaratorInitializers) {
						d.Initializer = ResolveInitializer (bc, d.Variable, d.Initializer);
						// d.Variable.DefinitelyAssigned 
					} 
				}
			}

			return true;
		}

		protected virtual Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
		{
			var a = new SimpleAssign (li.CreateReferenceExpression (bc, li.Location), initializer, li.Location);
			return a.ResolveStatement (bc);
		}

		protected override void DoEmit (EmitContext ec)
		{
			li.CreateBuilder (ec);

			if (Initializer != null && !IsUnreachable)
				((ExpressionStatement) Initializer).EmitStatement (ec);

			if (declarators != null) {
				foreach (var d in declarators) {
					d.Variable.CreateBuilder (ec);
					if (d.Initializer != null && !IsUnreachable) {
						ec.Mark (d.Variable.Location);
						((ExpressionStatement) d.Initializer).EmitStatement (ec);
					}
				}
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (Initializer != null)
				Initializer.FlowAnalysis (fc);

			if (declarators != null) {
				foreach (var d in declarators) {
					if (d.Initializer != null)
						d.Initializer.FlowAnalysis (fc);
				}
			}

			return false;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			var init = initializer as ExpressionStatement;
			if (init != null)
				init.MarkReachable (rc);

			return base.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			BlockVariable t = (BlockVariable) target;

			if (type_expr != null)
				t.type_expr = (FullNamedExpression) type_expr.Clone (clonectx);

			if (initializer != null)
				t.initializer = initializer.Clone (clonectx);

			if (declarators != null) {
				t.declarators = null;
				foreach (var d in declarators)
					t.AddDeclarator (d.Clone (clonectx));
			}
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class BlockConstant : BlockVariable
	{
		public BlockConstant (FullNamedExpression type, LocalVariable li)
			: base (type, li)
		{
		}

		public override void Emit (EmitContext ec)
		{
			// Nothing to emit, not even sequence point
		}

		protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
		{
			initializer = initializer.Resolve (bc);
			if (initializer == null)
				return null;

			var c = initializer as Constant;
			if (c == null) {
				initializer.Error_ExpressionMustBeConstant (bc, initializer.Location, li.Name);
				return null;
			}

			c = c.ConvertImplicitly (li.Type);
			if (c == null) {
				if (TypeSpec.IsReferenceType (li.Type))
					initializer.Error_ConstantCanBeInitializedWithNullOnly (bc, li.Type, initializer.Location, li.Name);
				else
					initializer.Error_ValueCannotBeConverted (bc, li.Type, false);

				return null;
			}

			li.ConstantValue = c;
			return initializer;
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	//
	// The information about a user-perceived local variable
	//
	public sealed class LocalVariable : INamedBlockVariable, ILocalVariable
	{
		[Flags]
		public enum Flags
		{
			Used = 1,
			IsThis = 1 << 1,
			AddressTaken = 1 << 2,
			CompilerGenerated = 1 << 3,
			Constant = 1 << 4,
			ForeachVariable = 1 << 5,
			FixedVariable = 1 << 6,
			UsingVariable = 1 << 7,
			IsLocked = 1 << 8,
			SymbolFileHidden = 1 << 9,

			ReadonlyMask = ForeachVariable | FixedVariable | UsingVariable
		}

		TypeSpec type;
		readonly string name;
		readonly Location loc;
		readonly Block block;
		Flags flags;
		Constant const_value;

		public VariableInfo VariableInfo;
		HoistedVariable hoisted_variant;

		LocalBuilder builder;

		public LocalVariable (Block block, string name, Location loc)
		{
			this.block = block;
			this.name = name;
			this.loc = loc;
		}

		public LocalVariable (Block block, string name, Flags flags, Location loc)
			: this (block, name, loc)
		{
			this.flags = flags;
		}

		//
		// Used by variable declarators
		//
		public LocalVariable (LocalVariable li, string name, Location loc)
			: this (li.block, name, li.flags, loc)
		{
		}

		#region Properties

		public bool AddressTaken {
			get {
				return (flags & Flags.AddressTaken) != 0;
			}
		}

		public Block Block {
			get {
				return block;
			}
		}

		public Constant ConstantValue {
			get {
				return const_value;
			}
			set {
				const_value = value;
			}
		}

		//
		// Hoisted local variable variant
		//
		public HoistedVariable HoistedVariant {
			get {
				return hoisted_variant;
			}
			set {
				hoisted_variant = value;
			}
		}

		public bool IsDeclared {
			get {
				return type != null;
			}
		}

		public bool IsCompilerGenerated {
			get {
				return (flags & Flags.CompilerGenerated) != 0;
			}
		}

		public bool IsConstant {
			get {
				return (flags & Flags.Constant) != 0;
			}
		}

		public bool IsLocked {
			get {
				return (flags & Flags.IsLocked) != 0;
			}
			set {
				flags = value ? flags | Flags.IsLocked : flags & ~Flags.IsLocked;
			}
		}

		public bool IsThis {
			get {
				return (flags & Flags.IsThis) != 0;
			}
		}

		public bool IsFixed {
			get {
				return (flags & Flags.FixedVariable) != 0;
			}
			set {
				flags = value ? flags | Flags.FixedVariable : flags & ~Flags.FixedVariable;
			}
		}

		bool INamedBlockVariable.IsParameter {
			get {
				return false;
			}
		}

		public bool IsReadonly {
			get {
				return (flags & Flags.ReadonlyMask) != 0;
			}
		}

		public Location Location {
			get {
				return loc;
			}
		}

		public string Name {
			get {
				return name;
			}
		}

		public TypeSpec Type {
		    get {
				return type;
			}
		    set {
				type = value;
			}
		}

		#endregion

		public void CreateBuilder (EmitContext ec)
		{
			if ((flags & Flags.Used) == 0) {
				if (VariableInfo == null) {
					// Missing flow analysis or wrong variable flags
					throw new InternalErrorException ("VariableInfo is null and the variable `{0}' is not used", name);
				}

				if (VariableInfo.IsEverAssigned)
					ec.Report.Warning (219, 3, Location, "The variable `{0}' is assigned but its value is never used", Name);
				else
					ec.Report.Warning (168, 3, Location, "The variable `{0}' is declared but never used", Name);
			}

			if (HoistedVariant != null)
				return;

			if (builder != null) {
				if ((flags & Flags.CompilerGenerated) != 0)
					return;

				// To avoid Used warning duplicates
				throw new InternalErrorException ("Already created variable `{0}'", name);
			}

			//
			// All fixed variabled are pinned, a slot has to be alocated
			//
			builder = ec.DeclareLocal (Type, IsFixed);
			if ((flags & Flags.SymbolFileHidden) == 0)
				ec.DefineLocalVariable (name, builder);
		}

		public static LocalVariable CreateCompilerGenerated (TypeSpec type, Block block, Location loc, bool writeToSymbolFile = false)
		{
			LocalVariable li = new LocalVariable (block, GetCompilerGeneratedName (block), Flags.CompilerGenerated | Flags.Used, loc);
			if (!writeToSymbolFile)
				li.flags |= Flags.SymbolFileHidden;
			
			li.Type = type;
			return li;
		}

		public Expression CreateReferenceExpression (ResolveContext rc, Location loc)
		{
			if (IsConstant && const_value != null)
				return Constant.CreateConstantFromValue (Type, const_value.GetValue (), loc);

			return new LocalVariableReference (this, loc);
		}

		public void Emit (EmitContext ec)
		{
			// TODO: Need something better for temporary variables
			if ((flags & Flags.CompilerGenerated) != 0)
				CreateBuilder (ec);

			ec.Emit (OpCodes.Ldloc, builder);
		}

		public void EmitAssign (EmitContext ec)
		{
			// TODO: Need something better for temporary variables
			if ((flags & Flags.CompilerGenerated) != 0)
				CreateBuilder (ec);

			ec.Emit (OpCodes.Stloc, builder);
		}

		public void EmitAddressOf (EmitContext ec)
		{
			// TODO: Need something better for temporary variables
			if ((flags & Flags.CompilerGenerated) != 0)
				CreateBuilder (ec);

			ec.Emit (OpCodes.Ldloca, builder);
		}

		public static string GetCompilerGeneratedName (Block block)
		{
			// HACK: Debugger depends on the name semantics
			return "$locvar" + block.ParametersBlock.TemporaryLocalsCount++.ToString ("X");
		}

		public string GetReadOnlyContext ()
		{
			switch (flags & Flags.ReadonlyMask) {
			case Flags.FixedVariable:
				return "fixed variable";
			case Flags.ForeachVariable:
				return "foreach iteration variable";
			case Flags.UsingVariable:
				return "using variable";
			}

			throw new InternalErrorException ("Variable is not readonly");
		}

		public bool IsThisAssigned (FlowAnalysisContext fc, Block block)
		{
			if (VariableInfo == null)
				throw new Exception ();

			if (IsAssigned (fc))
				return true;

			return VariableInfo.IsFullyInitialized (fc, block.StartLocation);
		}

		public bool IsAssigned (FlowAnalysisContext fc)
		{
			return fc.IsDefinitelyAssigned (VariableInfo);
		}

		public void PrepareAssignmentAnalysis (BlockContext bc)
		{
			//
			// No need to run assignment analysis for these guys
			//
			if ((flags & (Flags.Constant | Flags.ReadonlyMask | Flags.CompilerGenerated)) != 0)
				return;

			VariableInfo = VariableInfo.Create (bc, this);
		}

		//
		// Mark the variables as referenced in the user code
		//
		public void SetIsUsed ()
		{
			flags |= Flags.Used;
		}

		public void SetHasAddressTaken ()
		{
			flags |= (Flags.AddressTaken | Flags.Used);
		}

		public override string ToString ()
		{
			return string.Format ("LocalInfo ({0},{1},{2},{3})", name, type, VariableInfo, Location);
		}
	}

	/// <summary>
	///   Block represents a C# block.
	/// </summary>
	///
	/// <remarks>
	///   This class is used in a number of places: either to represent
	///   explicit blocks that the programmer places or implicit blocks.
	///
	///   Implicit blocks are used as labels or to introduce variable
	///   declarations.
	///
	///   Top-level blocks derive from Block, and they are called ToplevelBlock
	///   they contain extra information that is not necessary on normal blocks.
	/// </remarks>
	public class Block : Statement {
		[Flags]
		public enum Flags
		{
			Unchecked = 1,
			ReachableEnd = 8,
			Unsafe = 16,
			HasCapturedVariable = 64,
			HasCapturedThis = 1 << 7,
			IsExpressionTree = 1 << 8,
			CompilerGenerated = 1 << 9,
			HasAsyncModifier = 1 << 10,
			Resolved = 1 << 11,
			YieldBlock = 1 << 12,
			AwaitBlock = 1 << 13,
			FinallyBlock = 1 << 14,
			CatchBlock = 1 << 15,
			HasReferenceToStoreyForInstanceLambdas = 1 << 16,
			Iterator = 1 << 20,
			NoFlowAnalysis = 1 << 21,
			InitializationEmitted = 1 << 22
		}

		public Block Parent;
		public Location StartLocation;
		public Location EndLocation;

		public ExplicitBlock Explicit;
		public ParametersBlock ParametersBlock;

		protected Flags flags;

		//
		// The statements in this block
		//
		protected List<Statement> statements;

		protected List<Statement> scope_initializers;

		int? resolving_init_idx;

		Block original;

#if DEBUG
		static int id;
		public int ID = id++;

		static int clone_id_counter;
		int clone_id;
#endif

//		int assignable_slots;

		public Block (Block parent, Location start, Location end)
			: this (parent, 0, start, end)
		{
		}

		public Block (Block parent, Flags flags, Location start, Location end)
		{
			if (parent != null) {
				// the appropriate constructors will fixup these fields
				ParametersBlock = parent.ParametersBlock;
				Explicit = parent.Explicit;
			}
			
			this.Parent = parent;
			this.flags = flags;
			this.StartLocation = start;
			this.EndLocation = end;
			this.loc = start;
			statements = new List<Statement> (4);

			this.original = this;
		}

		#region Properties

		public Block Original {
			get {
				return original;
			}
			protected set {
				original = value;
			}
		}

		public bool IsCompilerGenerated {
			get { return (flags & Flags.CompilerGenerated) != 0; }
			set { flags = value ? flags | Flags.CompilerGenerated : flags & ~Flags.CompilerGenerated; }
		}


		public bool IsCatchBlock {
			get {
				return (flags & Flags.CatchBlock) != 0;
			}
		}

		public bool IsFinallyBlock {
			get {
				return (flags & Flags.FinallyBlock) != 0;
			}
		}

		public bool Unchecked {
			get { return (flags & Flags.Unchecked) != 0; }
			set { flags = value ? flags | Flags.Unchecked : flags & ~Flags.Unchecked; }
		}

		public bool Unsafe {
			get { return (flags & Flags.Unsafe) != 0; }
			set { flags |= Flags.Unsafe; }
		}

		public List<Statement> Statements {
			get { return statements; }
		}

		#endregion

		public void SetEndLocation (Location loc)
		{
			EndLocation = loc;
		}

		public void AddLabel (LabeledStatement target)
		{
			ParametersBlock.TopBlock.AddLabel (target.Name, target);
		}

		public void AddLocalName (LocalVariable li)
		{
			AddLocalName (li.Name, li);
		}

		public void AddLocalName (string name, INamedBlockVariable li)
		{
			ParametersBlock.TopBlock.AddLocalName (name, li, false);
		}

		public virtual void Error_AlreadyDeclared (string name, INamedBlockVariable variable, string reason)
		{
			if (reason == null) {
				Error_AlreadyDeclared (name, variable);
				return;
			}

			ParametersBlock.TopBlock.Report.Error (136, variable.Location,
				"A local variable named `{0}' cannot be declared in this scope because it would give a different meaning " +
				"to `{0}', which is already used in a `{1}' scope to denote something else",
				name, reason);
		}

		public virtual void Error_AlreadyDeclared (string name, INamedBlockVariable variable)
		{
			var pi = variable as ParametersBlock.ParameterInfo;
			if (pi != null) {
				pi.Parameter.Error_DuplicateName (ParametersBlock.TopBlock.Report);
			} else {
				ParametersBlock.TopBlock.Report.Error (128, variable.Location,
					"A local variable named `{0}' is already defined in this scope", name);
			}
		}
					
		public virtual void Error_AlreadyDeclaredTypeParameter (string name, Location loc)
		{
			ParametersBlock.TopBlock.Report.Error (412, loc,
				"The type parameter name `{0}' is the same as local variable or parameter name",
				name);
		}

		//
		// It should be used by expressions which require to
		// register a statement during resolve process.
		//
		public void AddScopeStatement (Statement s)
		{
			if (scope_initializers == null)
				scope_initializers = new List<Statement> ();

			//
			// Simple recursive helper, when resolve scope initializer another
			// new scope initializer can be added, this ensures it's initialized
			// before existing one. For now this can happen with expression trees
			// in base ctor initializer only
			//
			if (resolving_init_idx.HasValue) {
				scope_initializers.Insert (resolving_init_idx.Value, s);
				++resolving_init_idx;
			} else {
				scope_initializers.Add (s);
			}
		}

		public void InsertStatement (int index, Statement s)
		{
			statements.Insert (index, s);
		}
		
		public void AddStatement (Statement s)
		{
			statements.Add (s);
		}

		public LabeledStatement LookupLabel (string name)
		{
			return ParametersBlock.GetLabel (name, this);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			MarkReachableScope (rc);

			foreach (var s in statements) {
				rc = s.MarkReachable (rc);
				if (rc.IsUnreachable) {
					if ((flags & Flags.ReachableEnd) != 0)
						return new Reachability ();

					return rc;
				}
			}

			flags |= Flags.ReachableEnd;

			return rc;
		}

		public void MarkReachableScope (Reachability rc)
		{
			base.MarkReachable (rc);

			if (scope_initializers != null) {
				foreach (var si in scope_initializers)
					si.MarkReachable (rc);
			}
		}

		public override bool Resolve (BlockContext bc)
		{
			if ((flags & Flags.Resolved) != 0)
				return true;

			Block prev_block = bc.CurrentBlock;
			bc.CurrentBlock = this;

			//
			// Compiler generated scope statements
			//
			if (scope_initializers != null) {
				for (resolving_init_idx = 0; resolving_init_idx < scope_initializers.Count; ++resolving_init_idx) {
					scope_initializers[resolving_init_idx.Value].Resolve (bc);
				}

				resolving_init_idx = null;
			}

			bool ok = true;
			int statement_count = statements.Count;
			for (int ix = 0; ix < statement_count; ix++){
				Statement s = statements [ix];

				if (!s.Resolve (bc)) {
					ok = false;
					statements [ix] = new EmptyStatement (s.loc);
					continue;
				}
			}

			bc.CurrentBlock = prev_block;

			flags |= Flags.Resolved;
			return ok;
		}

		protected override void DoEmit (EmitContext ec)
		{
			for (int ix = 0; ix < statements.Count; ix++){
				statements [ix].Emit (ec);
			}
		}

		public override void Emit (EmitContext ec)
		{
			if (scope_initializers != null)
				EmitScopeInitializers (ec);

			DoEmit (ec);
		}

		protected void EmitScopeInitializers (EmitContext ec)
		{
			foreach (Statement s in scope_initializers)
				s.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (scope_initializers != null) {
				foreach (var si in scope_initializers)
					si.FlowAnalysis (fc);
			}

			return DoFlowAnalysis (fc, 0);	
		}

		bool DoFlowAnalysis (FlowAnalysisContext fc, int startIndex)
		{
			bool end_unreachable = !reachable;
			bool goto_flow_analysis = startIndex != 0;
			for (; startIndex < statements.Count; ++startIndex) {
				var s = statements[startIndex];

				end_unreachable = s.FlowAnalysis (fc);
				if (s.IsUnreachable) {
					statements [startIndex] = RewriteUnreachableStatement (s);
					continue;
				}

				//
				// Statement end reachability is needed mostly due to goto support. Consider
				//
				// if (cond) {
				//    goto X;
				// } else {
				//    goto Y;
				// }
				// X:
				//
				// X label is reachable only via goto not as another statement after if. We need
				// this for flow-analysis only to carry variable info correctly.
				//
				if (end_unreachable) {
					bool after_goto_case = goto_flow_analysis && s is GotoCase;

					var f = s as TryFinally;
					if (f != null && !f.FinallyBlock.HasReachableClosingBrace) {
						//
						// Special case for try-finally with unreachable code after
						// finally block. Try block has to include leave opcode but there is
						// no label to leave to after unreachable finally block closing
						// brace. This sentinel ensures there is always IL instruction to
						// leave to even if we know it'll never be reached.
						//
						statements.Insert (startIndex + 1, new SentinelStatement ());
					} else {
						for (++startIndex; startIndex < statements.Count; ++startIndex) {
							s = statements [startIndex];
							if (s is SwitchLabel) {
								if (!after_goto_case)
									s.FlowAnalysis (fc);

								break;
							}

							if (s.IsUnreachable) {
								s.FlowAnalysis (fc);
								statements [startIndex] = RewriteUnreachableStatement (s);
							}
						}
					}

					//
					// Idea is to stop after goto case because goto case will always have at least same
					// variable assigned as switch case label. This saves a lot for complex goto case tests
					//
					if (after_goto_case)
						break;

					continue;
				}

				var lb = s as LabeledStatement;
				if (lb != null && fc.AddReachedLabel (lb))
					break;
			}

			//
			// The condition should be true unless there is forward jumping goto
			// 
			// if (this is ExplicitBlock && end_unreachable != Explicit.HasReachableClosingBrace)
			//	Debug.Fail ();

			return !Explicit.HasReachableClosingBrace;
		}

		static Statement RewriteUnreachableStatement (Statement s)
		{
			// LAMESPEC: It's not clear whether declararion statement should be part of reachability
			// analysis. Even csc report unreachable warning for it but it's actually used hence
			// we try to emulate this behaviour
			//
			// Consider:
			// 	goto L;
			//	int v;
			// L:
			//	v = 1;

			if (s is BlockVariable || s is EmptyStatement || s is SentinelStatement)
				return s;

			return new EmptyStatement (s.loc);
		}

		public void ScanGotoJump (Statement label)
		{
			int i;
			for (i = 0; i < statements.Count; ++i) {
				if (statements[i] == label)
					break;
			}

			var rc = new Reachability ();
			for (++i; i < statements.Count; ++i) {
				var s = statements[i];
				rc = s.MarkReachable (rc);
				if (rc.IsUnreachable)
					return;
			}

			flags |= Flags.ReachableEnd;
		}

		public void ScanGotoJump (Statement label, FlowAnalysisContext fc)
		{
			int i;
			for (i = 0; i < statements.Count; ++i) {
				if (statements[i] == label)
					break;
			}

			DoFlowAnalysis (fc, ++i);
		}

#if DEBUG
		public override string ToString ()
		{
			return String.Format ("{0}: ID={1} Clone={2} Location={3}", GetType (), ID, clone_id != 0, StartLocation);
		}
#endif

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Block target = (Block) t;
#if DEBUG
			target.clone_id = ++clone_id_counter;
#endif

			clonectx.AddBlockMap (this, target);
			if (original != this)
				clonectx.AddBlockMap (original, target);

			target.ParametersBlock = (ParametersBlock) (ParametersBlock == this ? target : clonectx.RemapBlockCopy (ParametersBlock));
			target.Explicit = (ExplicitBlock) (Explicit == this ? target : clonectx.LookupBlock (Explicit));

			if (Parent != null)
				target.Parent = clonectx.RemapBlockCopy (Parent);

			target.statements = new List<Statement> (statements.Count);
			foreach (Statement s in statements)
				target.statements.Add (s.Clone (clonectx));
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class ExplicitBlock : Block
	{
		protected AnonymousMethodStorey am_storey;
		int debug_scope_index;

		public ExplicitBlock (Block parent, Location start, Location end)
			: this (parent, (Flags) 0, start, end)
		{
		}

		public ExplicitBlock (Block parent, Flags flags, Location start, Location end)
			: base (parent, flags, start, end)
		{
			this.Explicit = this;
		}

		#region Properties

		public AnonymousMethodStorey AnonymousMethodStorey {
			get {
				return am_storey;
			}
		}

		public bool HasAwait {
			get {
				return (flags & Flags.AwaitBlock) != 0;
			}
		}

		public bool HasCapturedThis {
			set {
				flags = value ? flags | Flags.HasCapturedThis : flags & ~Flags.HasCapturedThis;
			}
			get {
				return (flags & Flags.HasCapturedThis) != 0;
			}
		}

		//
		// Used to indicate that the block has reference to parent
		// block and cannot be made static when defining anonymous method
		//
		public bool HasCapturedVariable {
			set {
				flags = value ? flags | Flags.HasCapturedVariable : flags & ~Flags.HasCapturedVariable;
			}
			get {
				return (flags & Flags.HasCapturedVariable) != 0;
			}
		}

		public bool HasReachableClosingBrace {
		    get {
		        return (flags & Flags.ReachableEnd) != 0;
		    }
			set {
				flags = value ? flags | Flags.ReachableEnd : flags & ~Flags.ReachableEnd;
			}
		}

		public bool HasYield {
			get {
				return (flags & Flags.YieldBlock) != 0;
			}
		}

		#endregion

		//
		// Creates anonymous method storey in current block
		//
		public AnonymousMethodStorey CreateAnonymousMethodStorey (ResolveContext ec)
		{
			//
			// Return same story for iterator and async blocks unless we are
			// in nested anonymous method
			//
			if (ec.CurrentAnonymousMethod is StateMachineInitializer && ParametersBlock.Original == ec.CurrentAnonymousMethod.Block.Original)
				return ec.CurrentAnonymousMethod.Storey;

			if (am_storey == null) {
				MemberBase mc = ec.MemberContext as MemberBase;

				//
				// Creates anonymous method storey for this block
				//
				am_storey = new AnonymousMethodStorey (this, ec.CurrentMemberDefinition.Parent.PartialContainer, mc, ec.CurrentTypeParameters, "AnonStorey", MemberKind.Class);
			}

			return am_storey;
		}

		public void EmitScopeInitialization (EmitContext ec)
		{
			if ((flags & Flags.InitializationEmitted) != 0)
				return;

			if (am_storey != null) {
				DefineStoreyContainer (ec, am_storey);
				am_storey.EmitStoreyInstantiation (ec, this);
			}

			if (scope_initializers != null)
				EmitScopeInitializers (ec);

			flags |= Flags.InitializationEmitted;
		}

		public override void Emit (EmitContext ec)
		{
			if (Parent != null) {
				// TODO: It's needed only when scope has variable (normal or lifted)
				ec.BeginScope (GetDebugSymbolScopeIndex ());
			}

			EmitScopeInitialization (ec);

			if (ec.EmitAccurateDebugInfo && !IsCompilerGenerated && ec.Mark (StartLocation)) {
				ec.Emit (OpCodes.Nop);
			}

			DoEmit (ec);

			if (Parent != null)
				ec.EndScope ();

			if (ec.EmitAccurateDebugInfo && HasReachableClosingBrace && !(this is ParametersBlock) &&
				!IsCompilerGenerated && ec.Mark (EndLocation)) {
				ec.Emit (OpCodes.Nop);
			}
		}

		protected void DefineStoreyContainer (EmitContext ec, AnonymousMethodStorey storey)
		{
			if (ec.CurrentAnonymousMethod != null && ec.CurrentAnonymousMethod.Storey != null) {
				storey.SetNestedStoryParent (ec.CurrentAnonymousMethod.Storey);
				storey.Mutator = ec.CurrentAnonymousMethod.Storey.Mutator;
			}

			//
			// Creates anonymous method storey
			//
			storey.CreateContainer ();
			storey.DefineContainer ();

			if (Original.Explicit.HasCapturedThis && Original.ParametersBlock.TopBlock.ThisReferencesFromChildrenBlock != null) {

				//
				// Only first storey in path will hold this reference. All children blocks will
				// reference it indirectly using $ref field
				//
				for (Block b = Original.Explicit; b != null; b = b.Parent) {
					if (b.Parent != null) {
						var s = b.Parent.Explicit.AnonymousMethodStorey;
						if (s != null) {
							storey.HoistedThis = s.HoistedThis;
							break;
						}
					}

					if (b.Explicit == b.Explicit.ParametersBlock && b.Explicit.ParametersBlock.StateMachine != null) {
						if (storey.HoistedThis == null)
							storey.HoistedThis = b.Explicit.ParametersBlock.StateMachine.HoistedThis;

						if (storey.HoistedThis != null)
							break;
					}
				}

				//
				// We are the first storey on path and 'this' has to be hoisted
				//
				if (storey.HoistedThis == null || !(storey.Parent is HoistedStoreyClass)) {
					foreach (ExplicitBlock ref_block in Original.ParametersBlock.TopBlock.ThisReferencesFromChildrenBlock) {
						//
						// ThisReferencesFromChildrenBlock holds all reference even if they
						// are not on this path. It saves some memory otherwise it'd have to
						// be in every explicit block. We run this check to see if the reference
						// is valid for this storey
						//
						Block block_on_path = ref_block;
						for (; block_on_path != null && block_on_path != Original; block_on_path = block_on_path.Parent);

						if (block_on_path == null)
							continue;

						if (storey.HoistedThis == null) {
							storey.AddCapturedThisField (ec, null);
						}

						for (ExplicitBlock b = ref_block; b.AnonymousMethodStorey != storey; b = b.Parent.Explicit) {
							ParametersBlock pb;
							AnonymousMethodStorey b_storey = b.AnonymousMethodStorey;

							if (b_storey != null) {
								//
								// Don't add storey cross reference for `this' when the storey ends up not
								// beeing attached to any parent
								//
								if (b.ParametersBlock.StateMachine == null) {
									AnonymousMethodStorey s = null;
									for (Block ab = b.AnonymousMethodStorey.OriginalSourceBlock.Parent; ab != null; ab = ab.Parent) {
										s = ab.Explicit.AnonymousMethodStorey;
										if (s != null)
											break;
									}

									// Needs to be in sync with AnonymousMethodBody::DoCreateMethodHost
									if (s == null) {
										var parent = storey == null || storey.Kind == MemberKind.Struct ? null : storey;
										b.AnonymousMethodStorey.AddCapturedThisField (ec, parent);
										break;
									}

								}

								//
								// Stop propagation inside same top block
								//
								if (b.ParametersBlock == ParametersBlock.Original) {
									b_storey.AddParentStoreyReference (ec, storey);
//									b_storey.HoistedThis = storey.HoistedThis;
									break;
								}

								b = pb = b.ParametersBlock;
							} else {
								pb = b as ParametersBlock;
							}

							if (pb != null && pb.StateMachine != null) {
								if (pb.StateMachine == storey)
									break;

								//
								// If we are state machine with no parent. We can hook into parent without additional
								// reference and capture this directly
								//
								ExplicitBlock parent_storey_block = pb;
								while (parent_storey_block.Parent != null) {
									parent_storey_block = parent_storey_block.Parent.Explicit;
									if (parent_storey_block.AnonymousMethodStorey != null) {
										break;
									}
								}

								if (parent_storey_block.AnonymousMethodStorey == null) {
									if (pb.StateMachine.HoistedThis == null) {
										pb.StateMachine.AddCapturedThisField (ec, null);
										b.HasCapturedThis = true;
									}

									continue;
								}

								var parent_this_block = pb;
								while (parent_this_block.Parent != null) {
									parent_this_block = parent_this_block.Parent.ParametersBlock;
									if (parent_this_block.StateMachine != null && parent_this_block.StateMachine.HoistedThis != null) {
										break;
									}
								}

								//
								// Add reference to closest storey which holds captured this
								//
								pb.StateMachine.AddParentStoreyReference (ec, parent_this_block.StateMachine ?? storey);
							}

							//
							// Add parent storey reference only when this is not captured directly
							//
							if (b_storey != null) {
								b_storey.AddParentStoreyReference (ec, storey);
								b_storey.HoistedThis = storey.HoistedThis;
							}
						}
					}
				}
			}

			var ref_blocks = storey.ReferencesFromChildrenBlock;
			if (ref_blocks != null) {
				foreach (ExplicitBlock ref_block in ref_blocks) {
					for (ExplicitBlock b = ref_block; b.AnonymousMethodStorey != storey; b = b.Parent.Explicit) {
						if (b.AnonymousMethodStorey != null) {
							b.AnonymousMethodStorey.AddParentStoreyReference (ec, storey);

							//
							// Stop propagation inside same top block
							//
							if (b.ParametersBlock == ParametersBlock.Original)
								break;

							b = b.ParametersBlock;
						}

						var pb = b as ParametersBlock;
						if (pb != null && pb.StateMachine != null) {
							if (pb.StateMachine == storey)
								break;

							pb.StateMachine.AddParentStoreyReference (ec, storey);
						}

						b.HasCapturedVariable = true;
					}
				}
			}

			storey.Define ();
			storey.PrepareEmit ();
			storey.Parent.PartialContainer.AddCompilerGeneratedClass (storey);
		}

		public int GetDebugSymbolScopeIndex ()
		{
			if (debug_scope_index == 0)
				debug_scope_index = ++ParametersBlock.debug_scope_index;

			return debug_scope_index;
		}

		public void RegisterAsyncAwait ()
		{
			var block = this;
			while ((block.flags & Flags.AwaitBlock) == 0) {
				block.flags |= Flags.AwaitBlock;

				if (block is ParametersBlock)
					return;

				block = block.Parent.Explicit;
			}
		}

		public void RegisterIteratorYield ()
		{
			ParametersBlock.TopBlock.IsIterator = true;

			var block = this;
			while ((block.flags & Flags.YieldBlock) == 0) {
				block.flags |= Flags.YieldBlock;

				if (block.Parent == null)
					return;

				block = block.Parent.Explicit;
			}
		}

		public void SetCatchBlock ()
		{
			flags |= Flags.CatchBlock;
		}

		public void SetFinallyBlock ()
		{
			flags |= Flags.FinallyBlock;
		}

		public void WrapIntoDestructor (TryFinally tf, ExplicitBlock tryBlock)
		{
			tryBlock.statements = statements;
			statements = new List<Statement> (1);
			statements.Add (tf);
		}
	}

	//
	// ParametersBlock was introduced to support anonymous methods
	// and lambda expressions
	// 
	public class ParametersBlock : ExplicitBlock
	{
		public class ParameterInfo : INamedBlockVariable
		{
			readonly ParametersBlock block;
			readonly int index;
			public VariableInfo VariableInfo;
			bool is_locked;

			public ParameterInfo (ParametersBlock block, int index)
			{
				this.block = block;
				this.index = index;
			}

			#region Properties

			public ParametersBlock Block {
				get {
					return block;
				}
			}

			Block INamedBlockVariable.Block {
				get {
					return block;
				}
			}

			public bool IsDeclared {
				get {
					return true;
				}
			}

			public bool IsParameter {
				get {
					return true;
				}
			}

			public bool IsLocked {
				get {
					return is_locked;
				}
				set {
					is_locked = value;
				}
			}

			public Location Location {
				get {
					return Parameter.Location;
				}
			}

			public Parameter Parameter {
				get {
					return block.Parameters [index];
				}
			}

			public TypeSpec ParameterType {
				get {
					return Parameter.Type;
				}
			}

			#endregion

			public Expression CreateReferenceExpression (ResolveContext rc, Location loc)
			{
				return new ParameterReference (this, loc);
			}
		}

		// 
		// Block is converted into an expression
		//
		sealed class BlockScopeExpression : Expression
		{
			Expression child;
			readonly ParametersBlock block;

			public BlockScopeExpression (Expression child, ParametersBlock block)
			{
				this.child = child;
				this.block = block;
			}

			public override bool ContainsEmitWithAwait ()
			{
				return child.ContainsEmitWithAwait ();
			}

			public override Expression CreateExpressionTree (ResolveContext ec)
			{
				throw new NotSupportedException ();
			}

			protected override Expression DoResolve (ResolveContext ec)
			{
				if (child == null)
					return null;

				child = child.Resolve (ec);
				if (child == null)
					return null;

				eclass = child.eclass;
				type = child.Type;
				return this;
			}

			public override void Emit (EmitContext ec)
			{
				block.EmitScopeInitializers (ec);
				child.Emit (ec);
			}
		}

		protected ParametersCompiled parameters;
		protected ParameterInfo[] parameter_info;
		protected bool resolved;
		protected ToplevelBlock top_block;
		protected StateMachine state_machine;
		protected Dictionary<string, object> labels;

		public ParametersBlock (Block parent, ParametersCompiled parameters, Location start, Flags flags = 0)
			: base (parent, 0, start, start)
		{
			if (parameters == null)
				throw new ArgumentNullException ("parameters");

			this.parameters = parameters;
			ParametersBlock = this;

			this.flags |= flags | (parent.ParametersBlock.flags & (Flags.YieldBlock | Flags.AwaitBlock));

			this.top_block = parent.ParametersBlock.top_block;
			ProcessParameters ();
		}

		protected ParametersBlock (ParametersCompiled parameters, Location start)
			: base (null, 0, start, start)
		{
			if (parameters == null)
				throw new ArgumentNullException ("parameters");

			this.parameters = parameters;
			ParametersBlock = this;
		}

		//
		// It's supposed to be used by method body implementation of anonymous methods
		//
		protected ParametersBlock (ParametersBlock source, ParametersCompiled parameters)
			: base (null, 0, source.StartLocation, source.EndLocation)
		{
			this.parameters = parameters;
			this.statements = source.statements;
			this.scope_initializers = source.scope_initializers;

			this.resolved = true;
			this.reachable = source.reachable;
			this.am_storey = source.am_storey;
			this.state_machine = source.state_machine;
			this.flags = source.flags & Flags.ReachableEnd;

			ParametersBlock = this;

			//
			// Overwrite original for comparison purposes when linking cross references
			// between anonymous methods
			//
			Original = source.Original;
		}

		#region Properties

		public bool HasReferenceToStoreyForInstanceLambdas {
			get {
				return (flags & Flags.HasReferenceToStoreyForInstanceLambdas) != 0;
			}
			set {
				flags = value ? flags | Flags.HasReferenceToStoreyForInstanceLambdas : flags & ~Flags.HasReferenceToStoreyForInstanceLambdas;
			}
		}

		public bool IsAsync {
			get {
				return (flags & Flags.HasAsyncModifier) != 0;
			}
			set {
				flags = value ? flags | Flags.HasAsyncModifier : flags & ~Flags.HasAsyncModifier;
			}
		}

		//
		// Block has been converted to expression tree
		//
		public bool IsExpressionTree {
			get {
				return (flags & Flags.IsExpressionTree) != 0;
			}
		}

		//
		// The parameters for the block.
		//
		public ParametersCompiled Parameters {
			get {
				return parameters;
			}
		}

		public StateMachine StateMachine {
			get {
				return state_machine;
			}
		}

		public ToplevelBlock TopBlock {
			get {
				return top_block;
			}
			set {
				top_block = value;
			}
		}

		public bool Resolved {
			get {
				return (flags & Flags.Resolved) != 0;
			}
		}

		public int TemporaryLocalsCount { get; set; }

		#endregion

		//
		// Checks whether all `out' parameters have been assigned.
		//
		public void CheckControlExit (FlowAnalysisContext fc)
		{
			CheckControlExit (fc, fc.DefiniteAssignment);
		}

		public virtual void CheckControlExit (FlowAnalysisContext fc, DefiniteAssignmentBitSet dat)
		{
			if (parameter_info == null)
				return;

			foreach (var p in parameter_info) {
				if (p.VariableInfo == null)
					continue;

				if (p.VariableInfo.IsAssigned (dat))
					continue;

				fc.Report.Error (177, p.Location,
					"The out parameter `{0}' must be assigned to before control leaves the current method",
					p.Parameter.Name);
			}					
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			base.CloneTo (clonectx, t);

			var target = (ParametersBlock) t;

			//
			// Clone label statements as well as they contain block reference
			//
			var pb = this;
			while (true) {
				if (pb.labels != null) {
					target.labels = new Dictionary<string, object> ();

					foreach (var entry in pb.labels) {
						var list = entry.Value as List<LabeledStatement>;

						if (list != null) {
							var list_clone = new List<LabeledStatement> ();
							foreach (var lentry in list) {
								list_clone.Add (RemapLabeledStatement (lentry, clonectx.RemapBlockCopy (lentry.Block)));
							}

							target.labels.Add (entry.Key, list_clone);
						} else {
							var labeled = (LabeledStatement) entry.Value;
							target.labels.Add (entry.Key, RemapLabeledStatement (labeled, clonectx.RemapBlockCopy (labeled.Block)));
						}
					}

					break;
				}

				if (pb.Parent == null)
					break;

				pb = pb.Parent.ParametersBlock;
			}
		}

		public override Expression CreateExpressionTree (ResolveContext ec)
		{
			if (statements.Count == 1) {
				Expression expr = statements[0].CreateExpressionTree (ec);
				if (scope_initializers != null)
					expr = new BlockScopeExpression (expr, this);

				return expr;
			}

			return base.CreateExpressionTree (ec);
		}

		public override void Emit (EmitContext ec)
		{
			if (state_machine != null && state_machine.OriginalSourceBlock != this) {
				DefineStoreyContainer (ec, state_machine);
				state_machine.EmitStoreyInstantiation (ec, this);
			}

			base.Emit (ec);
		}

		public void EmitEmbedded (EmitContext ec)
		{
			if (state_machine != null && state_machine.OriginalSourceBlock != this) {
				DefineStoreyContainer (ec, state_machine);
				state_machine.EmitStoreyInstantiation (ec, this);
			}

			base.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			var res = base.DoFlowAnalysis (fc);

			if (HasReachableClosingBrace)
				CheckControlExit (fc);

			return res;
		}

		public LabeledStatement GetLabel (string name, Block block)
		{
			//
			// Cloned parameters blocks can have their own cloned version of top-level labels
			//
			if (labels == null) {
				if (Parent != null)
					return Parent.ParametersBlock.GetLabel (name, block);

				return null;
			}

			object value;
			if (!labels.TryGetValue (name, out value)) {
				return null;
			}

			var label = value as LabeledStatement;
			Block b = block;
			if (label != null) {
				if (IsLabelVisible (label, b))
					return label;

			} else {
				List<LabeledStatement> list = (List<LabeledStatement>) value;
				for (int i = 0; i < list.Count; ++i) {
					label = list[i];
					if (IsLabelVisible (label, b))
						return label;
				}
			}

			return null;
		}

		static bool IsLabelVisible (LabeledStatement label, Block b)
		{
			do {
				if (label.Block == b)
					return true;
				b = b.Parent;
			} while (b != null);

			return false;
		}

		public ParameterInfo GetParameterInfo (Parameter p)
		{
			for (int i = 0; i < parameters.Count; ++i) {
				if (parameters[i] == p)
					return parameter_info[i];
			}

			throw new ArgumentException ("Invalid parameter");
		}

		public ParameterReference GetParameterReference (int index, Location loc)
		{
			return new ParameterReference (parameter_info[index], loc);
		}

		public Statement PerformClone (ref HashSet<LocalVariable> undeclaredVariables)
		{
			undeclaredVariables = TopBlock.GetUndeclaredVariables ();

			CloneContext clonectx = new CloneContext ();
			return Clone (clonectx);
		}

		protected void ProcessParameters ()
		{
			if (parameters.Count == 0)
				return;

			parameter_info = new ParameterInfo[parameters.Count];
			for (int i = 0; i < parameter_info.Length; ++i) {
				var p = parameters.FixedParameters[i];
				if (p == null)
					continue;

				// TODO: Should use Parameter only and more block there
				parameter_info[i] = new ParameterInfo (this, i);
				if (p.Name != null)
					AddLocalName (p.Name, parameter_info[i]);
			}
		}

		LabeledStatement RemapLabeledStatement (LabeledStatement stmt, Block dst)
		{
			var src = stmt.Block;

			//
			// Cannot remap label block if the label was not yet cloned which
			// can happen in case of anonymous method inside anoynymous method
			// with a label. But in this case we don't care because goto cannot
			// jump of out anonymous method
			//
			if (src.ParametersBlock != this)
				return stmt;

			var src_stmts = src.Statements;
			for (int i = 0; i < src_stmts.Count; ++i) {
				if (src_stmts[i] == stmt)
					return (LabeledStatement) dst.Statements[i];
			}

			throw new InternalErrorException ("Should never be reached");
		}

		public override bool Resolve (BlockContext bc)
		{
			// TODO: if ((flags & Flags.Resolved) != 0)

			if (resolved)
				return true;

			resolved = true;

			if (bc.HasSet (ResolveContext.Options.ExpressionTreeConversion))
				flags |= Flags.IsExpressionTree;

			try {
				PrepareAssignmentAnalysis (bc);

				if (!base.Resolve (bc))
					return false;

			} catch (Exception e) {
				if (e is CompletionResult || bc.Report.IsDisabled || e is FatalException || bc.Report.Printer is NullReportPrinter || bc.Module.Compiler.Settings.BreakOnInternalError)
					throw;

				if (bc.CurrentBlock != null) {
					bc.Report.Error (584, bc.CurrentBlock.StartLocation, "Internal compiler error: {0}", e.Message);
				} else {
					bc.Report.Error (587, "Internal compiler error: {0}", e.Message);
				}
			}

			//
			// If an asynchronous body of F is either an expression classified as nothing, or a 
			// statement block where no return statements have expressions, the inferred return type is Task
			//
			if (IsAsync) {
				var am = bc.CurrentAnonymousMethod as AnonymousMethodBody;
				if (am != null && am.ReturnTypeInference != null && !am.ReturnTypeInference.HasBounds (0)) {
					am.ReturnTypeInference = null;
					am.ReturnType = bc.Module.PredefinedTypes.Task.TypeSpec;
					return true;
				}
			}

			return true;
		}

		void PrepareAssignmentAnalysis (BlockContext bc)
		{
			for (int i = 0; i < parameters.Count; ++i) {
				var par = parameters.FixedParameters[i];

				if ((par.ModFlags & Parameter.Modifier.OUT) == 0)
					continue;

				parameter_info [i].VariableInfo = VariableInfo.Create (bc, (Parameter) par);
			}
		}

		public ToplevelBlock ConvertToIterator (IMethodData method, TypeDefinition host, TypeSpec iterator_type, bool is_enumerable)
		{
			var iterator = new Iterator (this, method, host, iterator_type, is_enumerable);
			var stateMachine = new IteratorStorey (iterator);

			state_machine = stateMachine;
			iterator.SetStateMachine (stateMachine);

			var tlb = new ToplevelBlock (host.Compiler, Parameters, Location.Null, Flags.CompilerGenerated);
			tlb.Original = this;
			tlb.state_machine = stateMachine;
			tlb.AddStatement (new Return (iterator, iterator.Location));
			return tlb;
		}

		public ParametersBlock ConvertToAsyncTask (IMemberContext context, TypeDefinition host, ParametersCompiled parameters, TypeSpec returnType, TypeSpec delegateType, Location loc)
		{
			for (int i = 0; i < parameters.Count; i++) {
				Parameter p = parameters[i];
				Parameter.Modifier mod = p.ModFlags;
				if ((mod & Parameter.Modifier.RefOutMask) != 0) {
					host.Compiler.Report.Error (1988, p.Location,
						"Async methods cannot have ref or out parameters");
					return this;
				}

				if (p is ArglistParameter) {
					host.Compiler.Report.Error (4006, p.Location,
						"__arglist is not allowed in parameter list of async methods");
					return this;
				}

				if (parameters.Types[i].IsPointer) {
					host.Compiler.Report.Error (4005, p.Location,
						"Async methods cannot have unsafe parameters");
					return this;
				}
			}

			if (!HasAwait) {
				host.Compiler.Report.Warning (1998, 1, loc,
					"Async block lacks `await' operator and will run synchronously");
			}

			var block_type = host.Module.Compiler.BuiltinTypes.Void;
			var initializer = new AsyncInitializer (this, host, block_type);
			initializer.Type = block_type;
			initializer.DelegateType = delegateType;

			var stateMachine = new AsyncTaskStorey (this, context, initializer, returnType);

			state_machine = stateMachine;
			initializer.SetStateMachine (stateMachine);

			const Flags flags = Flags.CompilerGenerated;

			var b = this is ToplevelBlock ?
				new ToplevelBlock (host.Compiler, Parameters, Location.Null, flags) :
				new ParametersBlock (Parent, parameters, Location.Null, flags | Flags.HasAsyncModifier);

			b.Original = this;
			b.state_machine = stateMachine;
			b.AddStatement (new AsyncInitializerStatement (initializer));
			return b;
		}
	}

	//
	//
	//
	public class ToplevelBlock : ParametersBlock
	{
		LocalVariable this_variable;
		CompilerContext compiler;
		Dictionary<string, object> names;

		List<ExplicitBlock> this_references;

		public ToplevelBlock (CompilerContext ctx, Location loc)
			: this (ctx, ParametersCompiled.EmptyReadOnlyParameters, loc)
		{
		}

		public ToplevelBlock (CompilerContext ctx, ParametersCompiled parameters, Location start, Flags flags = 0)
			: base (parameters, start)
		{
			this.compiler = ctx;
			this.flags = flags;
			top_block = this;

			ProcessParameters ();
		}

		//
		// Recreates a top level block from parameters block. Used for
		// compiler generated methods where the original block comes from
		// explicit child block. This works for already resolved blocks
		// only to ensure we resolve them in the correct flow order
		//
		public ToplevelBlock (ParametersBlock source, ParametersCompiled parameters)
			: base (source, parameters)
		{
			this.compiler = source.TopBlock.compiler;
			top_block = this;
		}

		public bool IsIterator {
			get {
				return (flags & Flags.Iterator) != 0;
			}
			set {
				flags = value ? flags | Flags.Iterator : flags & ~Flags.Iterator;
			}
		}

		public Report Report {
			get {
				return compiler.Report;
			}
		}

		//
		// Used by anonymous blocks to track references of `this' variable
		//
		public List<ExplicitBlock> ThisReferencesFromChildrenBlock {
			get {
				return this_references;
			}
		}

		//
		// Returns the "this" instance variable of this block.
		// See AddThisVariable() for more information.
		//
		public LocalVariable ThisVariable {
			get {
				return this_variable;
			}
		}

		public void AddLocalName (string name, INamedBlockVariable li, bool ignoreChildrenBlocks)
		{
			if (names == null)
				names = new Dictionary<string, object> ();

			object value;
			if (!names.TryGetValue (name, out value)) {
				names.Add (name, li);
				return;
			}

			INamedBlockVariable existing = value as INamedBlockVariable;
			List<INamedBlockVariable> existing_list;
			if (existing != null) {
				existing_list = new List<INamedBlockVariable> ();
				existing_list.Add (existing);
				names[name] = existing_list;
			} else {
				existing_list = (List<INamedBlockVariable>) value;
			}

			//
			// A collision checking between local names
			//
			var variable_block = li.Block.Explicit;
			for (int i = 0; i < existing_list.Count; ++i) {
				existing = existing_list[i];
				Block b = existing.Block.Explicit;

				// Collision at same level
				if (variable_block == b) {
					li.Block.Error_AlreadyDeclared (name, li);
					break;
				}

				// Collision with parent
				Block parent = variable_block;
				while ((parent = parent.Parent) != null) {
					if (parent == b) {
						li.Block.Error_AlreadyDeclared (name, li, "parent or current");
						i = existing_list.Count;
						break;
					}
				}

				if (!ignoreChildrenBlocks && variable_block.Parent != b.Parent) {
					// Collision with children
					while ((b = b.Parent) != null) {
						if (variable_block == b) {
							li.Block.Error_AlreadyDeclared (name, li, "child");
							i = existing_list.Count;
							break;
						}
					}
				}
			}

			existing_list.Add (li);
		}

		public void AddLabel (string name, LabeledStatement label)
		{
			if (labels == null)
				labels = new Dictionary<string, object> ();

			object value;
			if (!labels.TryGetValue (name, out value)) {
				labels.Add (name, label);
				return;
			}

			LabeledStatement existing = value as LabeledStatement;
			List<LabeledStatement> existing_list;
			if (existing != null) {
				existing_list = new List<LabeledStatement> ();
				existing_list.Add (existing);
				labels[name] = existing_list;
			} else {
				existing_list = (List<LabeledStatement>) value;
			}

			//
			// A collision checking between labels
			//
			for (int i = 0; i < existing_list.Count; ++i) {
				existing = existing_list[i];
				Block b = existing.Block;

				// Collision at same level
				if (label.Block == b) {
					Report.SymbolRelatedToPreviousError (existing.loc, name);
					Report.Error (140, label.loc, "The label `{0}' is a duplicate", name);
					break;
				}

				// Collision with parent
				b = label.Block;
				while ((b = b.Parent) != null) {
					if (existing.Block == b) {
						Report.Error (158, label.loc,
							"The label `{0}' shadows another label by the same name in a contained scope", name);
						i = existing_list.Count;
						break;
					}
				}

				// Collision with with children
				b = existing.Block;
				while ((b = b.Parent) != null) {
					if (label.Block == b) {
						Report.Error (158, label.loc,
							"The label `{0}' shadows another label by the same name in a contained scope", name);
						i = existing_list.Count;
						break;
					}
				}
			}

			existing_list.Add (label);
		}

		public void AddThisReferenceFromChildrenBlock (ExplicitBlock block)
		{
			if (this_references == null)
				this_references = new List<ExplicitBlock> ();

			if (!this_references.Contains (block))
				this_references.Add (block);
		}

		public void RemoveThisReferenceFromChildrenBlock (ExplicitBlock block)
		{
			this_references.Remove (block);
		}

		//
		// Creates an arguments set from all parameters, useful for method proxy calls
		//
		public Arguments GetAllParametersArguments ()
		{
			int count = parameters.Count;
			Arguments args = new Arguments (count);
			for (int i = 0; i < count; ++i) {
				var pi = parameter_info[i];
				var arg_expr = GetParameterReference (i, pi.Location);

				Argument.AType atype_modifier;
				switch (pi.Parameter.ParameterModifier & Parameter.Modifier.RefOutMask) {
				case Parameter.Modifier.REF:
					atype_modifier = Argument.AType.Ref;
					break;
				case Parameter.Modifier.OUT:
					atype_modifier = Argument.AType.Out;
					break;
				default:
					atype_modifier = 0;
					break;
				}

				args.Add (new Argument (arg_expr, atype_modifier));
			}

			return args;
		}

		//
		// Lookup inside a block, the returned value can represent 3 states
		//
		// true+variable: A local name was found and it's valid
		// false+variable: A local name was found in a child block only
		// false+null: No local name was found
		//
		public bool GetLocalName (string name, Block block, ref INamedBlockVariable variable)
		{
			if (names == null)
				return false;

			object value;
			if (!names.TryGetValue (name, out value))
				return false;

			variable = value as INamedBlockVariable;
			Block b = block;
			if (variable != null) {
				do {
					if (variable.Block == b.Original)
						return true;

					b = b.Parent;
				} while (b != null);

				b = variable.Block;
				do {
					if (block == b)
						return false;

					b = b.Parent;
				} while (b != null);
			} else {
				List<INamedBlockVariable> list = (List<INamedBlockVariable>) value;
				for (int i = 0; i < list.Count; ++i) {
					variable = list[i];
					do {
						if (variable.Block == b.Original)
							return true;

						b = b.Parent;
					} while (b != null);

					b = variable.Block;
					do {
						if (block == b)
							return false;

						b = b.Parent;
					} while (b != null);

					b = block;
				}
			}

			variable = null;
			return false;
		}

		public void IncludeBlock (ParametersBlock pb, ToplevelBlock block)
		{
			if (block.names != null) {
				foreach (var n in block.names) {
					var variable = n.Value as INamedBlockVariable;
					if (variable != null) {
						if (variable.Block.ParametersBlock == pb)
							AddLocalName (n.Key, variable, false);
						continue;
					}

					foreach (var v in (List<INamedBlockVariable>) n.Value)
						if (v.Block.ParametersBlock == pb)
							AddLocalName (n.Key, v, false);
				}
			}
		}

		// <summary>
		//   This is used by non-static `struct' constructors which do not have an
		//   initializer - in this case, the constructor must initialize all of the
		//   struct's fields.  To do this, we add a "this" variable and use the flow
		//   analysis code to ensure that it's been fully initialized before control
		//   leaves the constructor.
		// </summary>
		public void AddThisVariable (BlockContext bc)
		{
			if (this_variable != null)
				throw new InternalErrorException (StartLocation.ToString ());

			this_variable = new LocalVariable (this, "this", LocalVariable.Flags.IsThis | LocalVariable.Flags.Used, StartLocation);
			this_variable.Type = bc.CurrentType;
			this_variable.PrepareAssignmentAnalysis (bc);
		}

		public override void CheckControlExit (FlowAnalysisContext fc, DefiniteAssignmentBitSet dat)
		{
			//
			// If we're a non-static struct constructor which doesn't have an
			// initializer, then we must initialize all of the struct's fields.
			//
			if (this_variable != null)
				this_variable.IsThisAssigned (fc, this);

			base.CheckControlExit (fc, dat);
		}

		public HashSet<LocalVariable> GetUndeclaredVariables ()
		{
			if (names == null)
				return null;

			HashSet<LocalVariable> variables = null;

			foreach (var entry in names) {
				var complex = entry.Value as List<INamedBlockVariable>;
				if (complex != null) {
					foreach (var centry in complex) {
						if (IsUndeclaredVariable (centry)) {
							if (variables == null)
								variables = new HashSet<LocalVariable> ();

							variables.Add ((LocalVariable) centry);
						}
					}
				} else if (IsUndeclaredVariable ((INamedBlockVariable)entry.Value)) {
					if (variables == null)
						variables = new HashSet<LocalVariable> ();

					variables.Add ((LocalVariable)entry.Value);					
				}
			}

			return variables;
		}

		static bool IsUndeclaredVariable (INamedBlockVariable namedBlockVariable)
		{
			var lv = namedBlockVariable as LocalVariable;
			return lv != null && !lv.IsDeclared;
		}

		public void SetUndeclaredVariables (HashSet<LocalVariable> undeclaredVariables)
		{
			if (names == null)
				return;
			
			foreach (var entry in names) {
				var complex = entry.Value as List<INamedBlockVariable>;
				if (complex != null) {
					foreach (var centry in complex) {
						var lv = centry as LocalVariable;
						if (lv != null && undeclaredVariables.Contains (lv)) {
							lv.Type = null;
						}
					}
				} else {
					var lv = entry.Value as LocalVariable;
					if (lv != null && undeclaredVariables.Contains (lv))
						lv.Type = null;
				}
			}
		}

		public override void Emit (EmitContext ec)
		{
			if (Report.Errors > 0)
				return;

			try {
			if (IsCompilerGenerated) {
				using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
					base.Emit (ec);
				}
			} else {
				base.Emit (ec);
			}

			//
			// If `HasReturnLabel' is set, then we already emitted a
			// jump to the end of the method, so we must emit a `ret'
			// there.
			//
			// Unfortunately, System.Reflection.Emit automatically emits
			// a leave to the end of a finally block.  This is a problem
			// if no code is following the try/finally block since we may
			// jump to a point after the end of the method.
			// As a workaround, we're always creating a return label in
			// this case.
			//
			if (ec.HasReturnLabel || HasReachableClosingBrace) {
				if (ec.HasReturnLabel)
					ec.MarkLabel (ec.ReturnLabel);

				if (ec.EmitAccurateDebugInfo && !IsCompilerGenerated)
					ec.Mark (EndLocation);

				if (ec.ReturnType.Kind != MemberKind.Void)
					ec.Emit (OpCodes.Ldloc, ec.TemporaryReturn ());

				ec.Emit (OpCodes.Ret);
			}

			} catch (Exception e) {
				throw new InternalErrorException (e, StartLocation);
			}
		}

		public bool Resolve (BlockContext bc, IMethodData md)
		{
			if (resolved)
				return true;

			var errors = bc.Report.Errors;

			base.Resolve (bc);

			if (bc.Report.Errors > errors)
				return false;

			MarkReachable (new Reachability ());

			if (HasReachableClosingBrace && bc.ReturnType.Kind != MemberKind.Void) {
				// TODO: var md = bc.CurrentMemberDefinition;
				bc.Report.Error (161, md.Location, "`{0}': not all code paths return a value", md.GetSignatureForError ());
			}

			if ((flags & Flags.NoFlowAnalysis) != 0)
				return true;

			var fc = new FlowAnalysisContext (bc.Module.Compiler, this, bc.AssignmentInfoOffset);
			try {
				FlowAnalysis (fc);
			} catch (Exception e) {
				throw new InternalErrorException (e, StartLocation);
			}

			return true;
		}
	}
	
	public class SwitchLabel : Statement
	{
		Constant converted;
		Expression label;

		Label? il_label;

		//
		// if expr == null, then it is the default case.
		//
		public SwitchLabel (Expression expr, Location l)
		{
			label = expr;
			loc = l;
		}

		public bool IsDefault {
			get {
				return label == null;
			}
		}

		public Expression Label {
			get {
				return label;
			}
		}

		public Location Location {
			get {
				return loc;
			}
		}

		public Constant Converted {
			get {
				return converted;
			}
			set {
				converted = value; 
			}
		}

		public bool PatternMatching { get; set; }

		public bool SectionStart { get; set; }

		public Label GetILLabel (EmitContext ec)
		{
			if (il_label == null){
				il_label = ec.DefineLabel ();
			}

			return il_label.Value;
		}

		protected override void DoEmit (EmitContext ec)
		{
			ec.MarkLabel (GetILLabel (ec));
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (!SectionStart)
				return false;

			fc.BranchDefiniteAssignment (fc.SwitchInitialDefinitiveAssignment);
			return false;
		}

		public override bool Resolve (BlockContext bc)
		{
			if (ResolveAndReduce (bc))
				bc.Switch.RegisterLabel (bc, this);

			return true;
		}

		//
		// Resolves the expression, reduces it to a literal if possible
		// and then converts it to the requested type.
		//
		bool ResolveAndReduce (BlockContext bc)
		{
			if (IsDefault)
				return true;

			var switch_statement = bc.Switch;

			if (PatternMatching) {
				label = new Is (switch_statement.ExpressionValue, label, loc).Resolve (bc);
				return label != null;
			}

			var c = label.ResolveLabelConstant (bc);
			if (c == null)
				return false;

			if (switch_statement.IsNullable && c is NullLiteral) {
				converted = c;
				return true;
			}

			if (switch_statement.IsPatternMatching) {
				label = new Is (switch_statement.ExpressionValue, label, loc).Resolve (bc);
				return true;
			}

			converted = c.ImplicitConversionRequired (bc, switch_statement.SwitchType);
			return converted != null;
		}

		public void Error_AlreadyOccurs (ResolveContext ec, SwitchLabel collision_with)
		{
			ec.Report.SymbolRelatedToPreviousError (collision_with.loc, null);
			ec.Report.Error (152, loc, "The label `{0}' already occurs in this switch statement", GetSignatureForError ());
		}

		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
			var t = (SwitchLabel) target;
			if (label != null)
				t.label = label.Clone (clonectx);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		public string GetSignatureForError ()
		{
			string label;
			if (converted == null)
				label = "default";
			else
				label = converted.GetValueAsLiteral ();

			return string.Format ("case {0}:", label);
		}
	}

	public class Switch : LoopStatement
	{
		// structure used to hold blocks of keys while calculating table switch
		sealed class LabelsRange : IComparable<LabelsRange>
		{
			public readonly long min;
			public long max;
			public readonly List<long> label_values;

			public LabelsRange (long value)
			{
				min = max = value;
				label_values = new List<long> ();
				label_values.Add (value);
			}

			public LabelsRange (long min, long max, ICollection<long> values)
			{
				this.min = min;
				this.max = max;
				this.label_values = new List<long> (values);
			}

			public long Range {
				get {
					return max - min + 1;
				}
			}

			public bool AddValue (long value)
			{
				var gap = value - min + 1;
				// Ensure the range has > 50% occupancy
				if (gap > 2 * (label_values.Count + 1) || gap <= 0)
					return false;

				max = value;
				label_values.Add (value);
				return true;
			}

			public int CompareTo (LabelsRange other)
			{
				int nLength = label_values.Count;
				int nLengthOther = other.label_values.Count;
				if (nLengthOther == nLength)
					return (int) (other.min - min);

				return nLength - nLengthOther;
			}
		}

		sealed class DispatchStatement : Statement
		{
			readonly Switch body;

			public DispatchStatement (Switch body)
			{
				this.body = body;
			}

			protected override void CloneTo (CloneContext clonectx, Statement target)
			{
				throw new NotImplementedException ();
			}

			protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
			{
				return false;
			}

			protected override void DoEmit (EmitContext ec)
			{
				body.EmitDispatch (ec);
			}
		}

		class MissingBreak : Statement
		{
			readonly SwitchLabel label;

			public MissingBreak (SwitchLabel sl)
			{
				this.label = sl;
				this.loc = sl.loc;
			}

			public bool FallOut { get; set; }

			protected override void DoEmit (EmitContext ec)
			{
			}

			protected override void CloneTo (CloneContext clonectx, Statement target)
			{
			}

			protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
			{
				if (FallOut) {
					fc.Report.Error (8070, loc, "Control cannot fall out of switch statement through final case label `{0}'",
						label.GetSignatureForError ());
				} else {
					fc.Report.Error (163, loc, "Control cannot fall through from one case label `{0}' to another",
						label.GetSignatureForError ());
				}
				return true;
			}
		}

		public Expression Expr;

		//
		// Mapping of all labels to their SwitchLabels
		//
		Dictionary<long, SwitchLabel> labels;
		Dictionary<string, SwitchLabel> string_labels;
		List<SwitchLabel> case_labels;

		List<Tuple<GotoCase, Constant>> goto_cases;
		List<DefiniteAssignmentBitSet> end_reachable_das;

		/// <summary>
		///   The governing switch type
		/// </summary>
		public TypeSpec SwitchType;

		Expression new_expr;

		SwitchLabel case_null;
		SwitchLabel case_default;

		Label defaultLabel, nullLabel;
		VariableReference value;
		ExpressionStatement string_dictionary;
		FieldExpr switch_cache_field;
		ExplicitBlock block;
		bool end_reachable;

		//
		// Nullable Types support
		//
		Nullable.Unwrap unwrap;

		public Switch (Expression e, ExplicitBlock block, Location l)
			: base (block)
		{
			Expr = e;
			this.block = block;
			loc = l;
		}

		public SwitchLabel ActiveLabel { get; set; }

		public ExplicitBlock Block {
			get {
				return block;
			}
		}

		public SwitchLabel DefaultLabel {
			get {
				return case_default;
			}
		}

		public bool IsNullable {
			get {
				return unwrap != null;
			}
		}

		public bool IsPatternMatching {
			get {
				return new_expr == null && SwitchType != null;
			}
		}

		public List<SwitchLabel> RegisteredLabels {
			get {
				return case_labels;
			}
		}

		public VariableReference ExpressionValue {
			get {
				return value;
			}
		}

		//
		// Determines the governing type for a switch.  The returned
		// expression might be the expression from the switch, or an
		// expression that includes any potential conversions to
		//
		static Expression SwitchGoverningType (ResolveContext rc, Expression expr, bool unwrapExpr)
		{
			switch (expr.Type.BuiltinType) {
			case BuiltinTypeSpec.Type.Byte:
			case BuiltinTypeSpec.Type.SByte:
			case BuiltinTypeSpec.Type.UShort:
			case BuiltinTypeSpec.Type.Short:
			case BuiltinTypeSpec.Type.UInt:
			case BuiltinTypeSpec.Type.Int:
			case BuiltinTypeSpec.Type.ULong:
			case BuiltinTypeSpec.Type.Long:
			case BuiltinTypeSpec.Type.Char:
			case BuiltinTypeSpec.Type.String:
			case BuiltinTypeSpec.Type.Bool:
				return expr;
			}

			if (expr.Type.IsEnum)
				return expr;

			//
			// Try to find a *user* defined implicit conversion.
			//
			// If there is no implicit conversion, or if there are multiple
			// conversions, we have to report an error
			//
			Expression converted = null;
			foreach (TypeSpec tt in rc.Module.PredefinedTypes.SwitchUserTypes) {

				if (!unwrapExpr && tt.IsNullableType && expr.Type.IsNullableType)
					break;

				var restr = Convert.UserConversionRestriction.ImplicitOnly |
					Convert.UserConversionRestriction.ProbingOnly;

				if (unwrapExpr)
					restr |= Convert.UserConversionRestriction.NullableSourceOnly;

				var e = Convert.UserDefinedConversion (rc, expr, tt, restr, Location.Null);
				if (e == null)
					continue;

				//
				// Ignore over-worked ImplicitUserConversions that do
				// an implicit conversion in addition to the user conversion.
				// 
				var uc = e as UserCast;
				if (uc == null)
					continue;

				if (converted != null){
//					rc.Report.ExtraInformation (loc, "(Ambiguous implicit user defined conversion in previous ");
					return null;
				}

				converted = e;
			}
			return converted;
		}

		public static TypeSpec[] CreateSwitchUserTypes (ModuleContainer module, TypeSpec nullable)
		{
			var types = module.Compiler.BuiltinTypes;

			// LAMESPEC: For some reason it does not contain bool which looks like csc bug
			TypeSpec[] stypes = new[] {
				types.SByte,
				types.Byte,
				types.Short,
				types.UShort,
				types.Int,
				types.UInt,
				types.Long,
				types.ULong,
				types.Char,
				types.String
			};

			if (nullable != null) {

				Array.Resize (ref stypes, stypes.Length + 9);

				for (int i = 0; i < 9; ++i) {
					stypes [10 + i] = nullable.MakeGenericType (module, new [] { stypes [i] });
				}
			}

			return stypes;
		}

		public void RegisterLabel (BlockContext rc, SwitchLabel sl)
		{
			case_labels.Add (sl);

			if (sl.IsDefault) {
				if (case_default != null) {
					sl.Error_AlreadyOccurs (rc, case_default);
				} else {
					case_default = sl;
				}

				return;
			}

			if (sl.Converted == null)
				return;

			try {
				if (string_labels != null) {
					string string_value = sl.Converted.GetValue () as string;
					if (string_value == null)
						case_null = sl;
					else
						string_labels.Add (string_value, sl);
				} else {
					if (sl.Converted.IsNull) {
						case_null = sl;
					} else {
						labels.Add (sl.Converted.GetValueAsLong (), sl);
					}
				}
			} catch (ArgumentException) {
				if (string_labels != null)
					sl.Error_AlreadyOccurs (rc, string_labels[(string) sl.Converted.GetValue ()]);
				else
					sl.Error_AlreadyOccurs (rc, labels[sl.Converted.GetValueAsLong ()]);
			}
		}
		
		//
		// This method emits code for a lookup-based switch statement (non-string)
		// Basically it groups the cases into blocks that are at least half full,
		// and then spits out individual lookup opcodes for each block.
		// It emits the longest blocks first, and short blocks are just
		// handled with direct compares.
		//
		void EmitTableSwitch (EmitContext ec, Expression val)
		{
			if (labels != null && labels.Count > 0) {
				List<LabelsRange> ranges;
				if (string_labels != null) {
					// We have done all hard work for string already
					// setup single range only
					ranges = new List<LabelsRange> (1);
					ranges.Add (new LabelsRange (0, labels.Count - 1, labels.Keys));
				} else {
					var element_keys = new long[labels.Count];
					labels.Keys.CopyTo (element_keys, 0);
					Array.Sort (element_keys);

					//
					// Build possible ranges of switch labes to reduce number
					// of comparisons
					//
					ranges = new List<LabelsRange> (element_keys.Length);
					var range = new LabelsRange (element_keys[0]);
					ranges.Add (range);
					for (int i = 1; i < element_keys.Length; ++i) {
						var l = element_keys[i];
						if (range.AddValue (l))
							continue;

						range = new LabelsRange (l);
						ranges.Add (range);
					}

					// sort the blocks so we can tackle the largest ones first
					ranges.Sort ();
				}

				Label lbl_default = defaultLabel;
				TypeSpec compare_type = SwitchType.IsEnum ? EnumSpec.GetUnderlyingType (SwitchType) : SwitchType;

				for (int range_index = ranges.Count - 1; range_index >= 0; --range_index) {
					LabelsRange kb = ranges[range_index];
					lbl_default = (range_index == 0) ? defaultLabel : ec.DefineLabel ();

					// Optimize small ranges using simple equality check
					if (kb.Range <= 2) {
						foreach (var key in kb.label_values) {
							SwitchLabel sl = labels[key];
							if (sl == case_default || sl == case_null)
								continue;

							if (sl.Converted.IsZeroInteger) {
								val.EmitBranchable (ec, sl.GetILLabel (ec), false);
							} else {
								val.Emit (ec);
								sl.Converted.Emit (ec);
								ec.Emit (OpCodes.Beq, sl.GetILLabel (ec));
							}
						}
					} else {
						// TODO: if all the keys in the block are the same and there are
						//       no gaps/defaults then just use a range-check.
						if (compare_type.BuiltinType == BuiltinTypeSpec.Type.Long || compare_type.BuiltinType == BuiltinTypeSpec.Type.ULong) {
							// TODO: optimize constant/I4 cases

							// check block range (could be > 2^31)
							val.Emit (ec);
							ec.EmitLong (kb.min);
							ec.Emit (OpCodes.Blt, lbl_default);

							val.Emit (ec);
							ec.EmitLong (kb.max);
							ec.Emit (OpCodes.Bgt, lbl_default);

							// normalize range
							val.Emit (ec);
							if (kb.min != 0) {
								ec.EmitLong (kb.min);
								ec.Emit (OpCodes.Sub);
							}

							ec.Emit (OpCodes.Conv_I4);	// assumes < 2^31 labels!
						} else {
							// normalize range
							val.Emit (ec);
							int first = (int) kb.min;
							if (first > 0) {
								ec.EmitInt (first);
								ec.Emit (OpCodes.Sub);
							} else if (first < 0) {
								ec.EmitInt (-first);
								ec.Emit (OpCodes.Add);
							}
						}

						// first, build the list of labels for the switch
						int iKey = 0;
						long cJumps = kb.Range;
						Label[] switch_labels = new Label[cJumps];
						for (int iJump = 0; iJump < cJumps; iJump++) {
							var key = kb.label_values[iKey];
							if (key == kb.min + iJump) {
								switch_labels[iJump] = labels[key].GetILLabel (ec);
								iKey++;
							} else {
								switch_labels[iJump] = lbl_default;
							}
						}

						// emit the switch opcode
						ec.Emit (OpCodes.Switch, switch_labels);
					}

					// mark the default for this block
					if (range_index != 0)
						ec.MarkLabel (lbl_default);
				}

				// the last default just goes to the end
				if (ranges.Count > 0)
					ec.Emit (OpCodes.Br, lbl_default);
			}
		}
		
		public SwitchLabel FindLabel (Constant value)
		{
			SwitchLabel sl = null;

			if (string_labels != null) {
				string s = value.GetValue () as string;
				if (s == null) {
					if (case_null != null)
						sl = case_null;
					else if (case_default != null)
						sl = case_default;
				} else {
					string_labels.TryGetValue (s, out sl);
				}
			} else {
				if (value is NullLiteral) {
					sl = case_null;
				} else {
					labels.TryGetValue (value.GetValueAsLong (), out sl);
				}
			}

			if (sl == null || sl.SectionStart)
				return sl;

			//
			// Always return section start, it simplifies handling of switch labels
			//
			for (int idx = case_labels.IndexOf (sl); ; --idx) {
				var cs = case_labels [idx];
				if (cs.SectionStart)
					return cs;
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			Expr.FlowAnalysis (fc);

			var prev_switch = fc.SwitchInitialDefinitiveAssignment;
			var InitialDefinitiveAssignment = fc.DefiniteAssignment;
			fc.SwitchInitialDefinitiveAssignment = InitialDefinitiveAssignment;

			block.FlowAnalysis (fc);

			fc.SwitchInitialDefinitiveAssignment = prev_switch;

			if (end_reachable_das != null) {
				var sections_das = DefiniteAssignmentBitSet.And (end_reachable_das);
				InitialDefinitiveAssignment |= sections_das;
				end_reachable_das = null;
			}

			fc.DefiniteAssignment = InitialDefinitiveAssignment;

			return case_default != null && !end_reachable;
		}

		public override bool Resolve (BlockContext ec)
		{
			Expr = Expr.Resolve (ec);
			if (Expr == null)
				return false;

			//
			// LAMESPEC: User conversion from non-nullable governing type has a priority
			//
			new_expr = SwitchGoverningType (ec, Expr, false);

			if (new_expr == null) {
				if (Expr.Type.IsNullableType) {
					unwrap = Nullable.Unwrap.Create (Expr, false);
					if (unwrap == null)
						return false;

					//
					// Unwrap + user conversion using non-nullable type is not allowed but user operator
					// involving nullable Expr and nullable governing type is
					//
					new_expr = SwitchGoverningType (ec, unwrap, true);
				}
			}

			Expression switch_expr;
			if (new_expr == null) {
				if (ec.Module.Compiler.Settings.Version != LanguageVersion.Experimental) {
					if (Expr.Type != InternalType.ErrorType) {
						ec.Report.Error (151, loc,
							"A switch expression of type `{0}' cannot be converted to an integral type, bool, char, string, enum or nullable type",
							Expr.Type.GetSignatureForError ());
					}

					return false;
				}

				switch_expr = Expr;
				SwitchType = Expr.Type;
			} else {
				switch_expr = new_expr;
				SwitchType = new_expr.Type;
				if (SwitchType.IsNullableType) {
					new_expr = unwrap = Nullable.Unwrap.Create (new_expr, true);
					SwitchType = Nullable.NullableInfo.GetUnderlyingType (SwitchType);
				}

				if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.Bool && ec.Module.Compiler.Settings.Version == LanguageVersion.ISO_1) {
					ec.Report.FeatureIsNotAvailable (ec.Module.Compiler, loc, "switch expression of boolean type");
					return false;
				}

				if (block.Statements.Count == 0)
					return true;

				if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.String) {
					string_labels = new Dictionary<string, SwitchLabel> ();
				} else {
					labels = new Dictionary<long, SwitchLabel> ();
				}
			}

			var constant = switch_expr as Constant;

			//
			// Don't need extra variable for constant switch or switch with
			// only default case
			//
			if (constant == null) {
				//
				// Store switch expression for comparison purposes
				//
				value = switch_expr as VariableReference;
				if (value == null && !HasOnlyDefaultSection ()) {
					var current_block = ec.CurrentBlock;
					ec.CurrentBlock = Block;
					// Create temporary variable inside switch scope
					value = TemporaryVariableReference.Create (SwitchType, ec.CurrentBlock, loc);
					value.Resolve (ec);
					ec.CurrentBlock = current_block;
				}
			}

			case_labels = new List<SwitchLabel> ();

			Switch old_switch = ec.Switch;
			ec.Switch = this;
			var parent_los = ec.EnclosingLoopOrSwitch;
			ec.EnclosingLoopOrSwitch = this;

			var ok = Statement.Resolve (ec);

			ec.EnclosingLoopOrSwitch = parent_los;
			ec.Switch = old_switch;

			//
			// Check if all goto cases are valid. Needs to be done after switch
			// is resolved because goto can jump forward in the scope.
			//
			if (goto_cases != null) {
				foreach (var gc in goto_cases) {
					if (gc.Item1 == null) {
						if (DefaultLabel == null) {
							Goto.Error_UnknownLabel (ec, "default", loc);
						}

						continue;
					}

					var sl = FindLabel (gc.Item2);
					if (sl == null) {
						Goto.Error_UnknownLabel (ec, "case " + gc.Item2.GetValueAsLiteral (), loc);
					} else {
						gc.Item1.Label = sl;
					}
				}
			}

			if (!ok)
				return false;

			if (constant == null && SwitchType.BuiltinType == BuiltinTypeSpec.Type.String && string_labels.Count > 6) {
				ResolveStringSwitchMap (ec);
			}

			//
			// Anonymous storey initialization has to happen before
			// any generated switch dispatch
			//
			block.InsertStatement (0, new DispatchStatement (this));

			return true;
		}

		bool HasOnlyDefaultSection ()
		{
			for (int i = 0; i < block.Statements.Count; ++i) {
				var s = block.Statements[i] as SwitchLabel;

				if (s == null || s.IsDefault)
					continue;

				return false;
			}

			return true;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			base.MarkReachable (rc);

			block.MarkReachableScope (rc);

			if (block.Statements.Count == 0)
				return rc;

			SwitchLabel constant_label = null;
			var constant = new_expr as Constant;

			if (constant != null) {
				constant_label = FindLabel (constant) ?? case_default;
				if (constant_label == null) {
					block.Statements.RemoveAt (0);
					return rc;
				}
			}

			var section_rc = new Reachability ();
			SwitchLabel prev_label = null;

			for (int i = 0; i < block.Statements.Count; ++i) {
				var s = block.Statements[i];
				var sl = s as SwitchLabel;

				if (sl != null && sl.SectionStart) {
					//
					// Section is marked already via goto case
					//
					if (!sl.IsUnreachable) {
						section_rc = new Reachability ();
						continue;
					}

					if (section_rc.IsUnreachable) {
						//
						// Common case. Previous label section end is unreachable as
						// it ends with break, return, etc. For next section revert
						// to reachable again unless we have constant switch block
						//
						section_rc = constant_label != null && constant_label != sl ?
							Reachability.CreateUnreachable () :
							new Reachability ();
					} else if (prev_label != null) {
						//
						// Error case as control cannot fall through from one case label
						//
						sl.SectionStart = false;
						s = new MissingBreak (prev_label);
						s.MarkReachable (rc);
						block.Statements.Insert (i - 1, s);
						++i;
					} else if (constant_label != null && constant_label != sl) {
						//
						// Special case for the first unreachable label in constant
						// switch block
						//
						section_rc = Reachability.CreateUnreachable ();
					}

					prev_label = sl;
				}

				section_rc = s.MarkReachable (section_rc);
			}

			if (!section_rc.IsUnreachable && prev_label != null) {
				prev_label.SectionStart = false;
				var s = new MissingBreak (prev_label) {
					FallOut = true
				};

				s.MarkReachable (rc);
				block.Statements.Add (s);
			}

			//
			// Reachability can affect parent only when all possible paths are handled but
			// we still need to run reachability check on switch body to check for fall-through
			//
			if (case_default == null && constant_label == null)
				return rc;

			//
			// We have at least one local exit from the switch
			//
			if (end_reachable)
				return rc;

			return Reachability.CreateUnreachable ();
		}

		public void RegisterGotoCase (GotoCase gotoCase, Constant value)
		{
			if (goto_cases == null)
				goto_cases = new List<Tuple<GotoCase, Constant>> ();

			goto_cases.Add (Tuple.Create (gotoCase, value));
		}

		//
		// Converts string switch into string hashtable
		//
		void ResolveStringSwitchMap (ResolveContext ec)
		{
			FullNamedExpression string_dictionary_type;
			if (ec.Module.PredefinedTypes.Dictionary.Define ()) {
				string_dictionary_type = new TypeExpression (
					ec.Module.PredefinedTypes.Dictionary.TypeSpec.MakeGenericType (ec,
						new [] { ec.BuiltinTypes.String, ec.BuiltinTypes.Int }),
					loc);
			} else if (ec.Module.PredefinedTypes.Hashtable.Define ()) {
				string_dictionary_type = new TypeExpression (ec.Module.PredefinedTypes.Hashtable.TypeSpec, loc);
			} else {
				ec.Module.PredefinedTypes.Dictionary.Resolve ();
				return;
			}

			var ctype = ec.CurrentMemberDefinition.Parent.PartialContainer;
			Field field = new Field (ctype, string_dictionary_type,
				Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
				new MemberName (CompilerGeneratedContainer.MakeName (null, "f", "switch$map", ec.Module.CounterSwitchTypes++), loc), null);
			if (!field.Define ())
				return;
			ctype.AddField (field);

			var init = new List<Expression> ();
			int counter = -1;
			labels = new Dictionary<long, SwitchLabel> (string_labels.Count);
			string value = null;

			foreach (SwitchLabel sl in case_labels) {

				if (sl.SectionStart)
					labels.Add (++counter, sl);

				if (sl == case_default || sl == case_null)
					continue;

				value = (string) sl.Converted.GetValue ();
				var init_args = new List<Expression> (2);
				init_args.Add (new StringLiteral (ec.BuiltinTypes, value, sl.Location));

				sl.Converted = new IntConstant (ec.BuiltinTypes, counter, loc);
				init_args.Add (sl.Converted);

				init.Add (new CollectionElementInitializer (init_args, loc));
			}
	
			Arguments args = new Arguments (1);
			args.Add (new Argument (new IntConstant (ec.BuiltinTypes, init.Count, loc)));
			Expression initializer = new NewInitialize (string_dictionary_type, args,
				new CollectionOrObjectInitializers (init, loc), loc);

			switch_cache_field = new FieldExpr (field, loc);
			string_dictionary = new SimpleAssign (switch_cache_field, initializer.Resolve (ec));
		}

		void DoEmitStringSwitch (EmitContext ec)
		{
			Label l_initialized = ec.DefineLabel ();

			//
			// Skip initialization when value is null
			//
			value.EmitBranchable (ec, nullLabel, false);

			//
			// Check if string dictionary is initialized and initialize
			//
			switch_cache_field.EmitBranchable (ec, l_initialized, true);
			using (ec.With (BuilderContext.Options.OmitDebugInfo, true)) {
				string_dictionary.EmitStatement (ec);
			}
			ec.MarkLabel (l_initialized);

			LocalTemporary string_switch_variable = new LocalTemporary (ec.BuiltinTypes.Int);

			ResolveContext rc = new ResolveContext (ec.MemberContext);

			if (switch_cache_field.Type.IsGeneric) {
				Arguments get_value_args = new Arguments (2);
				get_value_args.Add (new Argument (value));
				get_value_args.Add (new Argument (string_switch_variable, Argument.AType.Out));
				Expression get_item = new Invocation (new MemberAccess (switch_cache_field, "TryGetValue", loc), get_value_args).Resolve (rc);
				if (get_item == null)
					return;

				//
				// A value was not found, go to default case
				//
				get_item.EmitBranchable (ec, defaultLabel, false);
			} else {
				Arguments get_value_args = new Arguments (1);
				get_value_args.Add (new Argument (value));

				Expression get_item = new ElementAccess (switch_cache_field, get_value_args, loc).Resolve (rc);
				if (get_item == null)
					return;

				LocalTemporary get_item_object = new LocalTemporary (ec.BuiltinTypes.Object);
				get_item_object.EmitAssign (ec, get_item, true, false);
				ec.Emit (OpCodes.Brfalse, defaultLabel);

				ExpressionStatement get_item_int = (ExpressionStatement) new SimpleAssign (string_switch_variable,
					new Cast (new TypeExpression (ec.BuiltinTypes.Int, loc), get_item_object, loc)).Resolve (rc);

				get_item_int.EmitStatement (ec);
				get_item_object.Release (ec);
			}

			EmitTableSwitch (ec, string_switch_variable);
			string_switch_variable.Release (ec);
		}

		//
		// Emits switch using simple if/else comparison for small label count (4 + optional default)
		//
		void EmitShortSwitch (EmitContext ec)
		{
			MethodSpec equal_method = null;
			if (SwitchType.BuiltinType == BuiltinTypeSpec.Type.String) {
				equal_method = ec.Module.PredefinedMembers.StringEqual.Resolve (loc);
			}

			if (equal_method != null) {
				value.EmitBranchable (ec, nullLabel, false);
			}

			for (int i = 0; i < case_labels.Count; ++i) {
				var label = case_labels [i];
				if (label == case_default || label == case_null)
					continue;

				var constant = label.Converted;

				if (constant == null) {
					label.Label.EmitBranchable (ec, label.GetILLabel (ec), true);
					continue;
				}

				if (equal_method != null) {
					value.Emit (ec);
					constant.Emit (ec);

					var call = new CallEmitter ();
					call.EmitPredefined (ec, equal_method, new Arguments (0));
					ec.Emit (OpCodes.Brtrue, label.GetILLabel (ec));
					continue;
				}

				if (constant.IsZeroInteger && constant.Type.BuiltinType != BuiltinTypeSpec.Type.Long && constant.Type.BuiltinType != BuiltinTypeSpec.Type.ULong) {
					value.EmitBranchable (ec, label.GetILLabel (ec), false);
					continue;
				}

				value.Emit (ec);
				constant.Emit (ec);
				ec.Emit (OpCodes.Beq, label.GetILLabel (ec));
			}

			ec.Emit (OpCodes.Br, defaultLabel);
		}

		void EmitDispatch (EmitContext ec)
		{
			if (IsPatternMatching) {
				EmitShortSwitch (ec);
				return;
			}

			if (value == null) {
				//
				// Constant switch, we've already done the work if there is only 1 label
				// referenced
				//
				int reachable = 0;
				foreach (var sl in case_labels) {
					if (sl.IsUnreachable)
						continue;

					if (reachable++ > 0) {
						var constant = (Constant) new_expr;
						var constant_label = FindLabel (constant) ?? case_default;

						ec.Emit (OpCodes.Br, constant_label.GetILLabel (ec));
						break;
					}
				}

				return;
			}

			if (string_dictionary != null) {
				DoEmitStringSwitch (ec);
			} else if (case_labels.Count < 4 || string_labels != null) {
				EmitShortSwitch (ec);
			} else {
				EmitTableSwitch (ec, value);
			}
		}

		protected override void DoEmit (EmitContext ec)
		{
			//
			// Setup the codegen context
			//
			Label old_end = ec.LoopEnd;
			Switch old_switch = ec.Switch;

			ec.LoopEnd = ec.DefineLabel ();
			ec.Switch = this;

			defaultLabel = case_default == null ? ec.LoopEnd : case_default.GetILLabel (ec);
			nullLabel = case_null == null ? defaultLabel : case_null.GetILLabel (ec);

			if (value != null) {
				ec.Mark (loc);

				var switch_expr = new_expr ?? Expr;
				if (IsNullable) {
					unwrap.EmitCheck (ec);
					ec.Emit (OpCodes.Brfalse, nullLabel);
					value.EmitAssign (ec, switch_expr, false, false);
				} else if (switch_expr != value) {
					value.EmitAssign (ec, switch_expr, false, false);
				}


				//
				// Next statement is compiler generated we don't need extra
				// nop when we can use the statement for sequence point
				//
				ec.Mark (block.StartLocation);
				block.IsCompilerGenerated = true;
			} else {
				new_expr.EmitSideEffect (ec);
			}

			block.Emit (ec);

			// Restore context state. 
			ec.MarkLabel (ec.LoopEnd);

			//
			// Restore the previous context
			//
			ec.LoopEnd = old_end;
			ec.Switch = old_switch;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Switch target = (Switch) t;

			target.Expr = Expr.Clone (clonectx);
			target.Statement = target.block = (ExplicitBlock) block.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

		public override void AddEndDefiniteAssignment (FlowAnalysisContext fc)
		{
			if (case_default == null && !(new_expr is Constant))
				return;

			if (end_reachable_das == null)
				end_reachable_das = new List<DefiniteAssignmentBitSet> ();

			end_reachable_das.Add (fc.DefiniteAssignment);
		}

		public override void SetEndReachable ()
		{
			end_reachable = true;
		}
	}

	// A place where execution can restart in a state machine
	public abstract class ResumableStatement : Statement
	{
		bool prepared;
		protected Label resume_point;

		public Label PrepareForEmit (EmitContext ec)
		{
			if (!prepared) {
				prepared = true;
				resume_point = ec.DefineLabel ();
			}
			return resume_point;
		}

		public virtual Label PrepareForDispose (EmitContext ec, Label end)
		{
			return end;
		}

		public virtual void EmitForDispose (EmitContext ec, LocalBuilder pc, Label end, bool have_dispatcher)
		{
		}
	}

	public abstract class TryFinallyBlock : ExceptionStatement
	{
		protected Statement stmt;
		Label dispose_try_block;
		bool prepared_for_dispose, emitted_dispose;
		Method finally_host;

		protected TryFinallyBlock (Statement stmt, Location loc)
			: base (loc)
		{
			this.stmt = stmt;
		}

		#region Properties

		public Statement Statement {
			get {
				return stmt;
			}
		}

		#endregion

		protected abstract void EmitTryBody (EmitContext ec);
		public abstract void EmitFinallyBody (EmitContext ec);

		public override Label PrepareForDispose (EmitContext ec, Label end)
		{
			if (!prepared_for_dispose) {
				prepared_for_dispose = true;
				dispose_try_block = ec.DefineLabel ();
			}
			return dispose_try_block;
		}

		protected sealed override void DoEmit (EmitContext ec)
		{
			EmitTryBodyPrepare (ec);
			EmitTryBody (ec);

			bool beginFinally = EmitBeginFinallyBlock (ec);

			Label start_finally = ec.DefineLabel ();
			if (resume_points != null && beginFinally) {
				var state_machine = (StateMachineInitializer) ec.CurrentAnonymousMethod;

				ec.Emit (OpCodes.Ldloc, state_machine.SkipFinally);
				ec.Emit (OpCodes.Brfalse_S, start_finally);
				ec.Emit (OpCodes.Endfinally);
			}

			ec.MarkLabel (start_finally);

			if (finally_host != null) {
				finally_host.Define ();
				finally_host.PrepareEmit ();
				finally_host.Emit ();

				// Now it's safe to add, to close it properly and emit sequence points
				finally_host.Parent.AddMember (finally_host);

				var ce = new CallEmitter ();
				ce.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
				ce.EmitPredefined (ec, finally_host.Spec, new Arguments (0), true);
			} else {
				EmitFinallyBody (ec);
			}

			if (beginFinally)
				ec.EndExceptionBlock ();
		}

		public override void EmitForDispose (EmitContext ec, LocalBuilder pc, Label end, bool have_dispatcher)
		{
			if (emitted_dispose)
				return;

			emitted_dispose = true;

			Label end_of_try = ec.DefineLabel ();

			// Ensure that the only way we can get into this code is through a dispatcher
			if (have_dispatcher)
				ec.Emit (OpCodes.Br, end);

			ec.BeginExceptionBlock ();

			ec.MarkLabel (dispose_try_block);

			Label[] labels = null;
			for (int i = 0; i < resume_points.Count; ++i) {
				ResumableStatement s = resume_points[i];
				Label ret = s.PrepareForDispose (ec, end_of_try);
				if (ret.Equals (end_of_try) && labels == null)
					continue;
				if (labels == null) {
					labels = new Label[resume_points.Count];
					for (int j = 0; j < i; ++j)
						labels[j] = end_of_try;
				}
				labels[i] = ret;
			}

			if (labels != null) {
				int j;
				for (j = 1; j < labels.Length; ++j)
					if (!labels[0].Equals (labels[j]))
						break;
				bool emit_dispatcher = j < labels.Length;

				if (emit_dispatcher) {
					ec.Emit (OpCodes.Ldloc, pc);
					ec.EmitInt (first_resume_pc);
					ec.Emit (OpCodes.Sub);
					ec.Emit (OpCodes.Switch, labels);
				}

				foreach (ResumableStatement s in resume_points)
					s.EmitForDispose (ec, pc, end_of_try, emit_dispatcher);
			}

			ec.MarkLabel (end_of_try);

			ec.BeginFinallyBlock ();

			if (finally_host != null) {
				var ce = new CallEmitter ();
				ce.InstanceExpression = new CompilerGeneratedThis (ec.CurrentType, loc);
				ce.EmitPredefined (ec, finally_host.Spec, new Arguments (0), true);
			} else {
				EmitFinallyBody (ec);
			}

			ec.EndExceptionBlock ();
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			var res = stmt.FlowAnalysis (fc);
			parent_try_block = null;
			return res;
		}

		protected virtual bool EmitBeginFinallyBlock (EmitContext ec)
		{
			ec.BeginFinallyBlock ();
			return true;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Statement.MarkReachable (rc);
		}

		public override bool Resolve (BlockContext bc)
		{
			bool ok;

			parent_try_block = bc.CurrentTryBlock;
			bc.CurrentTryBlock = this;

			if (stmt is TryCatch) {
				ok = stmt.Resolve (bc);
			} else {
				using (bc.Set (ResolveContext.Options.TryScope)) {
					ok = stmt.Resolve (bc);
				}
			}

			bc.CurrentTryBlock = parent_try_block;

			//
			// Finally block inside iterator is called from MoveNext and
			// Dispose methods that means we need to lift the block into
			// newly created host method to emit the body only once. The
			// original block then simply calls the newly generated method.
			//
			if (bc.CurrentIterator != null && !bc.IsInProbingMode) {
				var b = stmt as Block;
				if (b != null && b.Explicit.HasYield) {
					finally_host = bc.CurrentIterator.CreateFinallyHost (this);
				}
			}

			return base.Resolve (bc) && ok;
		}
	}

	//
	// Base class for blocks using exception handling
	//
	public abstract class ExceptionStatement : ResumableStatement
	{
		protected List<ResumableStatement> resume_points;
		protected int first_resume_pc;
		protected ExceptionStatement parent_try_block;
		protected int first_catch_resume_pc = -1;

		protected ExceptionStatement (Location loc)
		{
			this.loc = loc;
		}

		protected virtual void EmitTryBodyPrepare (EmitContext ec)
		{
			StateMachineInitializer state_machine = null;
			if (resume_points != null) {
				state_machine = (StateMachineInitializer) ec.CurrentAnonymousMethod;

				ec.EmitInt ((int) IteratorStorey.State.Running);
				ec.Emit (OpCodes.Stloc, state_machine.CurrentPC);
			}

			//
			// The resume points in catch section when this is try-catch-finally
			//
			if (IsRewrittenTryCatchFinally ()) {
				ec.BeginExceptionBlock ();

				if (first_catch_resume_pc >= 0) {

					ec.MarkLabel (resume_point);

					// For normal control flow, we want to fall-through the Switch
					// So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
					ec.Emit (OpCodes.Ldloc, state_machine.CurrentPC);
					ec.EmitInt (first_resume_pc + first_catch_resume_pc);
					ec.Emit (OpCodes.Sub);

					var labels = new Label [resume_points.Count - first_catch_resume_pc];
					for (int i = 0; i < labels.Length; ++i)
						labels [i] = resume_points [i + first_catch_resume_pc].PrepareForEmit (ec);
					ec.Emit (OpCodes.Switch, labels);
				}
			}

			ec.BeginExceptionBlock ();

			//
			// The resume points for try section
			//
			if (resume_points != null && first_catch_resume_pc != 0) {
				if (first_catch_resume_pc < 0)
					ec.MarkLabel (resume_point);

				// For normal control flow, we want to fall-through the Switch
				// So, we use CurrentPC rather than the $PC field, and initialize it to an outside value above
				ec.Emit (OpCodes.Ldloc, state_machine.CurrentPC);
				ec.EmitInt (first_resume_pc);
				ec.Emit (OpCodes.Sub);

				var labels = new Label [first_catch_resume_pc > 0 ? first_catch_resume_pc : resume_points.Count];
				for (int i = 0; i < labels.Length; ++i)
					labels[i] = resume_points[i].PrepareForEmit (ec);
				ec.Emit (OpCodes.Switch, labels);
			}
		}

		bool IsRewrittenTryCatchFinally ()
		{
			var tf = this as TryFinally;
			if (tf == null)
				return false;

			var tc = tf.Statement as TryCatch;
			if (tc == null)
				return false;

			return tf.FinallyBlock.HasAwait || tc.HasClauseWithAwait;
		}

		public int AddResumePoint (ResumableStatement stmt, int pc, StateMachineInitializer stateMachine, TryCatch catchBlock)
		{
			if (parent_try_block != null) {
				pc = parent_try_block.AddResumePoint (this, pc, stateMachine, catchBlock);
			} else {
				pc = stateMachine.AddResumePoint (this);
			}

			if (resume_points == null) {
				resume_points = new List<ResumableStatement> ();
				first_resume_pc = pc;
			}

			if (pc != first_resume_pc + resume_points.Count)
				throw new InternalErrorException ("missed an intervening AddResumePoint?");

			var tf = this as TryFinally;
			if (tf != null && tf.Statement == catchBlock && first_catch_resume_pc < 0) {
				first_catch_resume_pc = resume_points.Count;
			}

			resume_points.Add (stmt);
			return pc;
		}
	}

	public class Lock : TryFinallyBlock
	{
		Expression expr;
		TemporaryVariableReference expr_copy;
		TemporaryVariableReference lock_taken;
			
		public Lock (Expression expr, Statement stmt, Location loc)
			: base (stmt, loc)
		{
			this.expr = expr;
		}

		public Expression Expr {
			get {
 				return this.expr;
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			expr.FlowAnalysis (fc);
			return base.DoFlowAnalysis (fc);
		}

		public override bool Resolve (BlockContext ec)
		{
			expr = expr.Resolve (ec);
			if (expr == null)
				return false;

			if (!TypeSpec.IsReferenceType (expr.Type) && expr.Type != InternalType.ErrorType) {
				ec.Report.Error (185, loc,
					"`{0}' is not a reference type as required by the lock statement",
					expr.Type.GetSignatureForError ());
			}

			if (expr.Type.IsGenericParameter) {
				expr = Convert.ImplicitTypeParameterConversion (expr, (TypeParameterSpec)expr.Type, ec.BuiltinTypes.Object);
			}

			VariableReference lv = expr as VariableReference;
			bool locked;
			if (lv != null) {
				locked = lv.IsLockedByStatement;
				lv.IsLockedByStatement = true;
			} else {
				lv = null;
				locked = false;
			}

			//
			// Have to keep original lock value around to unlock same location
			// in the case of original value has changed or is null
			//
			expr_copy = TemporaryVariableReference.Create (ec.BuiltinTypes.Object, ec.CurrentBlock, loc);
			expr_copy.Resolve (ec);

			//
			// Ensure Monitor methods are available
			//
			if (ResolvePredefinedMethods (ec) > 1) {
				lock_taken = TemporaryVariableReference.Create (ec.BuiltinTypes.Bool, ec.CurrentBlock, loc);
				lock_taken.Resolve (ec);
			}

			using (ec.Set (ResolveContext.Options.LockScope)) {
				base.Resolve (ec);
			}

			if (lv != null) {
				lv.IsLockedByStatement = locked;
			}

			return true;
		}
		
		protected override void EmitTryBodyPrepare (EmitContext ec)
		{
			expr_copy.EmitAssign (ec, expr);

			if (lock_taken != null) {
				//
				// Initialize ref variable
				//
				lock_taken.EmitAssign (ec, new BoolLiteral (ec.BuiltinTypes, false, loc));
			} else {
				//
				// Monitor.Enter (expr_copy)
				//
				expr_copy.Emit (ec);
				ec.Emit (OpCodes.Call, ec.Module.PredefinedMembers.MonitorEnter.Get ());
			}

			base.EmitTryBodyPrepare (ec);
		}

		protected override void EmitTryBody (EmitContext ec)
		{
			//
			// Monitor.Enter (expr_copy, ref lock_taken)
			//
			if (lock_taken != null) {
				expr_copy.Emit (ec);
				lock_taken.LocalInfo.CreateBuilder (ec);
				lock_taken.AddressOf (ec, AddressOp.Load);
				ec.Emit (OpCodes.Call, ec.Module.PredefinedMembers.MonitorEnter_v4.Get ());
			}

			Statement.Emit (ec);
		}

		public override void EmitFinallyBody (EmitContext ec)
		{
			//
			// if (lock_taken) Monitor.Exit (expr_copy)
			//
			Label skip = ec.DefineLabel ();

			if (lock_taken != null) {
				lock_taken.Emit (ec);
				ec.Emit (OpCodes.Brfalse_S, skip);
			}

			expr_copy.Emit (ec);
			var m = ec.Module.PredefinedMembers.MonitorExit.Resolve (loc);
			if (m != null)
				ec.Emit (OpCodes.Call, m);

			ec.MarkLabel (skip);
		}

		int ResolvePredefinedMethods (ResolveContext rc)
		{
			// Try 4.0 Monitor.Enter (object, ref bool) overload first
			var m = rc.Module.PredefinedMembers.MonitorEnter_v4.Get ();
			if (m != null)
				return 4;

			m = rc.Module.PredefinedMembers.MonitorEnter.Get ();
			if (m != null)
				return 1;

			rc.Module.PredefinedMembers.MonitorEnter_v4.Resolve (loc);
			return 0;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Lock target = (Lock) t;

			target.expr = expr.Clone (clonectx);
			target.stmt = Statement.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}

	}

	public class Unchecked : Statement {
		public Block Block;
		
		public Unchecked (Block b, Location loc)
		{
			Block = b;
			b.Unchecked = true;
			this.loc = loc;
		}

		public override bool Resolve (BlockContext ec)
		{
			using (ec.With (ResolveContext.Options.AllCheckStateFlags, false))
				return Block.Resolve (ec);
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			using (ec.With (EmitContext.Options.CheckedScope, false))
				Block.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return Block.FlowAnalysis (fc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Block.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Unchecked target = (Unchecked) t;

			target.Block = clonectx.LookupBlock (Block);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Checked : Statement {
		public Block Block;
		
		public Checked (Block b, Location loc)
		{
			Block = b;
			b.Unchecked = false;
			this.loc = loc;
		}

		public override bool Resolve (BlockContext ec)
		{
			using (ec.With (ResolveContext.Options.AllCheckStateFlags, true))
				return Block.Resolve (ec);
		}

		protected override void DoEmit (EmitContext ec)
		{
			using (ec.With (EmitContext.Options.CheckedScope, true))
				Block.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return Block.FlowAnalysis (fc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Block.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Checked target = (Checked) t;

			target.Block = clonectx.LookupBlock (Block);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Unsafe : Statement {
		public Block Block;

		public Unsafe (Block b, Location loc)
		{
			Block = b;
			Block.Unsafe = true;
			this.loc = loc;
		}

		public override bool Resolve (BlockContext ec)
		{
			if (ec.CurrentIterator != null)
				ec.Report.Error (1629, loc, "Unsafe code may not appear in iterators");

			using (ec.Set (ResolveContext.Options.UnsafeScope))
				return Block.Resolve (ec);
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			Block.Emit (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			return Block.FlowAnalysis (fc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);
			return Block.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Unsafe target = (Unsafe) t;

			target.Block = clonectx.LookupBlock (Block);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	// 
	// Fixed statement
	//
	public class Fixed : Statement
	{
		abstract class Emitter : ShimExpression
		{
			protected LocalVariable vi;

			protected Emitter (Expression expr, LocalVariable li)
				: base (expr)
			{
				vi = li;
			}

			public abstract void EmitExit (EmitContext ec);

			public override void FlowAnalysis (FlowAnalysisContext fc)
			{
				expr.FlowAnalysis (fc);
			}
		}

		sealed class ExpressionEmitter : Emitter {
			public ExpressionEmitter (Expression converted, LocalVariable li)
				: base (converted, li)
			{
			}

			protected override Expression DoResolve (ResolveContext rc)
			{
				throw new NotImplementedException ();
			}

			public override void Emit (EmitContext ec) {
				//
				// Store pointer in pinned location
				//
				expr.Emit (ec);
				vi.EmitAssign (ec);
			}

			public override void EmitExit (EmitContext ec)
			{
				ec.EmitInt (0);
				ec.Emit (OpCodes.Conv_U);
				vi.EmitAssign (ec);
			}
		}

		class StringEmitter : Emitter
		{
			LocalVariable pinned_string;

			public StringEmitter (Expression expr, LocalVariable li)
				: base (expr, li)
			{
			}

			protected override Expression DoResolve (ResolveContext rc)
			{
				pinned_string = new LocalVariable (vi.Block, "$pinned",
					LocalVariable.Flags.FixedVariable | LocalVariable.Flags.CompilerGenerated | LocalVariable.Flags.Used,
					vi.Location);
				pinned_string.Type = rc.BuiltinTypes.String;
				vi.IsFixed = false;

				eclass = ExprClass.Variable;
				type = rc.BuiltinTypes.Int;
				return this;
			}

			public override void Emit (EmitContext ec)
			{
				pinned_string.CreateBuilder (ec);

				expr.Emit (ec);
				pinned_string.EmitAssign (ec);

				// TODO: Should use Binary::Add
				pinned_string.Emit (ec);
				ec.Emit (OpCodes.Conv_I);

				var m = ec.Module.PredefinedMembers.RuntimeHelpersOffsetToStringData.Resolve (loc);
				if (m == null)
					return;

				PropertyExpr pe = new PropertyExpr (m, pinned_string.Location);
				//pe.InstanceExpression = pinned_string;
				pe.Resolve (new ResolveContext (ec.MemberContext)).Emit (ec);

				ec.Emit (OpCodes.Add);
				vi.EmitAssign (ec);
			}

			public override void EmitExit (EmitContext ec)
			{
				ec.EmitNull ();
				pinned_string.EmitAssign (ec);
			}
		}

		public class VariableDeclaration : BlockVariable
		{
			public VariableDeclaration (FullNamedExpression type, LocalVariable li)
				: base (type, li)
			{
			}

			protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
			{
				if (!Variable.Type.IsPointer && li == Variable) {
					bc.Report.Error (209, TypeExpression.Location,
						"The type of locals declared in a fixed statement must be a pointer type");
					return null;
				}

				var res = initializer.Resolve (bc);
				if (res == null)
					return null;

				//
				// Case 1: Array
				//
				var ac = res.Type as ArrayContainer;
				if (ac != null) {
					TypeSpec array_type = ac.Element;

					//
					// Provided that array_type is unmanaged,
					//
					if (!TypeManager.VerifyUnmanaged (bc.Module, array_type, loc))
						return null;

					Expression res_init;
					if (ExpressionAnalyzer.IsInexpensiveLoad (res)) {
						res_init = res;
					} else {
						var expr_variable = LocalVariable.CreateCompilerGenerated (ac, bc.CurrentBlock, loc);
						res_init = new CompilerAssign (expr_variable.CreateReferenceExpression (bc, loc), res, loc);
						res = expr_variable.CreateReferenceExpression (bc, loc);
					}

					//
					// and T* is implicitly convertible to the
					// pointer type given in the fixed statement.
					//
					ArrayPtr array_ptr = new ArrayPtr (res, array_type, loc);

					Expression converted = Convert.ImplicitConversionRequired (bc, array_ptr.Resolve (bc), li.Type, loc);
					if (converted == null)
						return null;

					//
					// fixed (T* e_ptr = (e == null || e.Length == 0) ? null : converted [0])
					//
					converted = new Conditional (new BooleanExpression (new Binary (Binary.Operator.LogicalOr,
						new Binary (Binary.Operator.Equality, res_init, new NullLiteral (loc)),
						new Binary (Binary.Operator.Equality, new MemberAccess (res, "Length"), new IntConstant (bc.BuiltinTypes, 0, loc)))),
							new NullLiteral (loc),
							converted, loc);

					converted = converted.Resolve (bc);

					return new ExpressionEmitter (converted, li);
				}

				//
				// Case 2: string
				//
				if (res.Type.BuiltinType == BuiltinTypeSpec.Type.String) {
					return new StringEmitter (res, li).Resolve (bc);
				}

				// Case 3: fixed buffer
				if (res is FixedBufferPtr) {
					return new ExpressionEmitter (res, li);
				}

				bool already_fixed = true;

				//
				// Case 4: & object.
				//
				Unary u = res as Unary;
				if (u != null) {
					if (u.Oper == Unary.Operator.AddressOf) {
						IVariableReference vr = u.Expr as IVariableReference;
						if (vr == null || !vr.IsFixed) {
							already_fixed = false;
						}
					}
				} else if (initializer is Cast) {
					bc.Report.Error (254, initializer.Location, "The right hand side of a fixed statement assignment may not be a cast expression");
					return null;
				}

				if (already_fixed) {
					bc.Report.Error (213, loc, "You cannot use the fixed statement to take the address of an already fixed expression");
				}

				res = Convert.ImplicitConversionRequired (bc, res, li.Type, loc);
				return new ExpressionEmitter (res, li);
			}
		}


		VariableDeclaration decl;
		Statement statement;
		bool has_ret;

		public Fixed (VariableDeclaration decl, Statement stmt, Location l)
		{
			this.decl = decl;
			statement = stmt;
			loc = l;
		}

		#region Properties

		public Statement Statement {
			get {
				return statement;
			}
		}

		public BlockVariable Variables {
			get {
				return decl;
			}
		}

		#endregion

		public override bool Resolve (BlockContext bc)
		{
			using (bc.Set (ResolveContext.Options.FixedInitializerScope)) {
				if (!decl.Resolve (bc))
					return false;
			}

			return statement.Resolve (bc);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			decl.FlowAnalysis (fc);
			return statement.FlowAnalysis (fc);
		}
		
		protected override void DoEmit (EmitContext ec)
		{
			decl.Variable.CreateBuilder (ec);
			decl.Initializer.Emit (ec);
			if (decl.Declarators != null) {
				foreach (var d in decl.Declarators) {
					d.Variable.CreateBuilder (ec);
					d.Initializer.Emit (ec);
				}
			}

			statement.Emit (ec);

			if (has_ret)
				return;

			//
			// Clear the pinned variable
			//
			((Emitter) decl.Initializer).EmitExit (ec);
			if (decl.Declarators != null) {
				foreach (var d in decl.Declarators) {
					((Emitter)d.Initializer).EmitExit (ec);
				}
			}
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			decl.MarkReachable (rc);

			rc = statement.MarkReachable (rc);

			// TODO: What if there is local exit?
			has_ret = rc.IsUnreachable;
			return rc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Fixed target = (Fixed) t;

			target.decl = (VariableDeclaration) decl.Clone (clonectx);
			target.statement = statement.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Catch : Statement
	{
		class CatchVariableStore : Statement
		{
			readonly Catch ctch;

			public CatchVariableStore (Catch ctch)
			{
				this.ctch = ctch;
			}

			protected override void CloneTo (CloneContext clonectx, Statement target)
			{
			}

			protected override void DoEmit (EmitContext ec)
			{
				// Emits catch variable debug information inside correct block
				ctch.EmitCatchVariableStore (ec);
			}

			protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
			{
				return true;
			}
		}

		class FilterStatement : Statement
		{
			readonly Catch ctch;

			public FilterStatement (Catch ctch)
			{
				this.ctch = ctch;
			}

			protected override void CloneTo (CloneContext clonectx, Statement target)
			{
			}

			protected override void DoEmit (EmitContext ec)
			{
				if (ctch.li != null) {
					if (ctch.hoisted_temp != null)
						ctch.hoisted_temp.Emit (ec);
					else
						ctch.li.Emit (ec);

					if (!ctch.IsGeneral && ctch.type.Kind == MemberKind.TypeParameter)
						ec.Emit (OpCodes.Box, ctch.type);
				}

				var expr_start = ec.DefineLabel ();
				var end = ec.DefineLabel ();

				ec.Emit (OpCodes.Brtrue_S, expr_start);
				ec.EmitInt (0);
				ec.Emit (OpCodes.Br, end);
				ec.MarkLabel (expr_start);

				ctch.Filter.Emit (ec);

				ec.MarkLabel (end);
				ec.Emit (OpCodes.Endfilter);
				ec.BeginFilterHandler ();
				ec.Emit (OpCodes.Pop);
			}

			protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
			{
				ctch.Filter.FlowAnalysis (fc);
				return true;
			}

			public override bool Resolve (BlockContext bc)
			{
				ctch.Filter = ctch.Filter.Resolve (bc);

				if (ctch.Filter != null) {
					if (ctch.Filter.ContainsEmitWithAwait ()) {
						bc.Report.Error (7094, ctch.Filter.Location, "The `await' operator cannot be used in the filter expression of a catch clause");
					}

					var c = ctch.Filter as Constant;
					if (c != null && !c.IsDefaultValue) {
						bc.Report.Warning (7095, 1, ctch.Filter.Location, "Exception filter expression is a constant");
					}
				}

				return true;
			}
		}

		ExplicitBlock block;
		LocalVariable li;
		FullNamedExpression type_expr;
		CompilerAssign assign;
		TypeSpec type;
		LocalTemporary hoisted_temp;

		public Catch (ExplicitBlock block, Location loc)
		{
			this.block = block;
			this.loc = loc;
		}

		#region Properties

		public ExplicitBlock Block {
			get {
				return block;
			}
		}

		public TypeSpec CatchType {
			get {
				return type;
			}
		}

		public Expression Filter {
			get; set;
		}

		public bool IsGeneral {
			get {
				return type_expr == null;
			}
		}

		public FullNamedExpression TypeExpression {
			get {
				return type_expr;
			}
			set {
				type_expr = value;
			}
		}

		public LocalVariable Variable {
			get {
				return li;
			}
			set {
				li = value;
			}
		}

		#endregion

		protected override void DoEmit (EmitContext ec)
		{
			if (Filter != null) {
				ec.BeginExceptionFilterBlock ();
				ec.Emit (OpCodes.Isinst, IsGeneral ? ec.BuiltinTypes.Object : CatchType);

				if (Block.HasAwait) {
					Block.EmitScopeInitialization (ec);
				} else {
					Block.Emit (ec);
				}

				return;
			}

			if (IsGeneral)
				ec.BeginCatchBlock (ec.BuiltinTypes.Object);
			else
				ec.BeginCatchBlock (CatchType);

			if (li == null)
				ec.Emit (OpCodes.Pop);

			if (Block.HasAwait) {
				if (li != null)
					EmitCatchVariableStore (ec);
			} else {
				Block.Emit (ec);
			}
		}

		void EmitCatchVariableStore (EmitContext ec)
		{
			li.CreateBuilder (ec);

			//
			// For hoisted catch variable we have to use a temporary local variable
			// for captured variable initialization during storey setup because variable
			// needs to be on the stack after storey instance for stfld operation
			//
			if (li.HoistedVariant != null) {
				hoisted_temp = new LocalTemporary (li.Type);
				hoisted_temp.Store (ec);

				// switch to assignment from temporary variable and not from top of the stack
				assign.UpdateSource (hoisted_temp);
			}
		}

		public override bool Resolve (BlockContext bc)
		{
			using (bc.Set (ResolveContext.Options.CatchScope)) {
				if (type_expr == null) {
					if (CreateExceptionVariable (bc.Module.Compiler.BuiltinTypes.Object)) {
						if (!block.HasAwait || Filter != null)
							block.AddScopeStatement (new CatchVariableStore (this));

						Expression source = new EmptyExpression (li.Type);
						assign = new CompilerAssign (new LocalVariableReference (li, Location.Null), source, Location.Null);
						Block.AddScopeStatement (new StatementExpression (assign, Location.Null));
					}
				} else {
					type = type_expr.ResolveAsType (bc);
					if (type == null)
						return false;

					if (li == null)
						CreateExceptionVariable (type);

					if (type.BuiltinType != BuiltinTypeSpec.Type.Exception && !TypeSpec.IsBaseClass (type, bc.BuiltinTypes.Exception, false)) {
						bc.Report.Error (155, loc, "The type caught or thrown must be derived from System.Exception");
					} else if (li != null) {
						li.Type = type;
						li.PrepareAssignmentAnalysis (bc);

						// source variable is at the top of the stack
						Expression source = new EmptyExpression (li.Type);
						if (li.Type.IsGenericParameter)
							source = new UnboxCast (source, li.Type);

						if (!block.HasAwait || Filter != null)
							block.AddScopeStatement (new CatchVariableStore (this));

						//
						// Uses Location.Null to hide from symbol file
						//
						assign = new CompilerAssign (new LocalVariableReference (li, Location.Null), source, Location.Null);
						Block.AddScopeStatement (new StatementExpression (assign, Location.Null));
					}
				}

				if (Filter != null) {
					Block.AddScopeStatement (new FilterStatement (this));
				}

				Block.SetCatchBlock ();
				return Block.Resolve (bc);
			}
		}

		bool CreateExceptionVariable (TypeSpec type)
		{
			if (!Block.HasAwait)
				return false;

			// TODO: Scan the block for rethrow expression
			//if (!Block.HasRethrow)
			//	return;

			li = LocalVariable.CreateCompilerGenerated (type, block, Location.Null);
			return true;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			if (li != null && !li.IsCompilerGenerated) {
				fc.SetVariableAssigned (li.VariableInfo, true);
			}

			return block.FlowAnalysis (fc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			var c = Filter as Constant;
			if (c != null && c.IsDefaultValue)
				return Reachability.CreateUnreachable ();

			return block.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Catch target = (Catch) t;

			if (type_expr != null)
				target.type_expr = (FullNamedExpression) type_expr.Clone (clonectx);

			if (Filter != null)
				target.Filter = Filter.Clone (clonectx);

			target.block = (ExplicitBlock) clonectx.LookupBlock (block);
		}
	}

	public class TryFinally : TryFinallyBlock
	{
		ExplicitBlock fini;
		List<DefiniteAssignmentBitSet> try_exit_dat;
		List<Label> redirected_jumps;
		Label? start_fin_label;

		public TryFinally (Statement stmt, ExplicitBlock fini, Location loc)
			 : base (stmt, loc)
		{
			this.fini = fini;
		}

		public ExplicitBlock FinallyBlock {
			get {
 				return fini;
			}
		}

		public void RegisterForControlExitCheck (DefiniteAssignmentBitSet vector)
		{
			if (try_exit_dat == null)
				try_exit_dat = new List<DefiniteAssignmentBitSet> ();

			try_exit_dat.Add (vector);
		}

		public override bool Resolve (BlockContext bc)
		{
			bool ok = base.Resolve (bc);

			fini.SetFinallyBlock ();
			using (bc.Set (ResolveContext.Options.FinallyScope)) {
				ok &= fini.Resolve (bc);
			}

			return ok;
		}

		protected override void EmitTryBody (EmitContext ec)
		{
			if (fini.HasAwait) {
				if (ec.TryFinallyUnwind == null)
					ec.TryFinallyUnwind = new List<TryFinally> ();

				ec.TryFinallyUnwind.Add (this);
				stmt.Emit (ec);

				if (first_catch_resume_pc < 0 && stmt is TryCatch)
					ec.EndExceptionBlock ();

				ec.TryFinallyUnwind.Remove (this);

				if (start_fin_label != null)
					ec.MarkLabel (start_fin_label.Value);

				return;
			}

			stmt.Emit (ec);
		}

		protected override bool EmitBeginFinallyBlock (EmitContext ec)
		{
			if (fini.HasAwait)
				return false;

			return base.EmitBeginFinallyBlock (ec);
		}

		public override void EmitFinallyBody (EmitContext ec)
		{
			if (!fini.HasAwait) {
				fini.Emit (ec);
				return;
			}

			//
			// Emits catch block like
			//
			// catch (object temp) {
			//	this.exception_field = temp;
			// }
			//
			var type = ec.BuiltinTypes.Object;
			ec.BeginCatchBlock (type);

			var temp = ec.GetTemporaryLocal (type);
			ec.Emit (OpCodes.Stloc, temp);

			var exception_field = ec.GetTemporaryField (type);
			exception_field.AutomaticallyReuse = false;
			ec.EmitThis ();
			ec.Emit (OpCodes.Ldloc, temp);
			exception_field.EmitAssignFromStack (ec);

			ec.EndExceptionBlock ();

			ec.FreeTemporaryLocal (temp, type);

			fini.Emit (ec);

			//
			// Emits exception rethrow
			//
			// if (this.exception_field != null)
			//	throw this.exception_field;
			//
			exception_field.Emit (ec);
			var skip_throw = ec.DefineLabel ();
			ec.Emit (OpCodes.Brfalse_S, skip_throw);
			exception_field.Emit (ec);
			ec.Emit (OpCodes.Throw);
			ec.MarkLabel (skip_throw);

			exception_field.PrepareCleanup (ec);

			EmitUnwindFinallyTable (ec);
		}

		bool IsParentBlock (Block block)
		{
			for (Block b = fini; b != null; b = b.Parent) {
				if (b == block)
					return true;
			}

			return false;
		}

		public static Label EmitRedirectedJump (EmitContext ec, AsyncInitializer initializer, Label label, Block labelBlock)
		{
			int idx;
			if (labelBlock != null) {
				for (idx = ec.TryFinallyUnwind.Count; idx != 0; --idx) {
					var fin = ec.TryFinallyUnwind [idx - 1];
					if (!fin.IsParentBlock (labelBlock))
						break;
				}
			} else {
				idx = 0;
			}

			bool set_return_state = true;

			for (; idx < ec.TryFinallyUnwind.Count; ++idx) {
				var fin = ec.TryFinallyUnwind [idx];
				if (labelBlock != null && !fin.IsParentBlock (labelBlock))
					break;

				fin.EmitRedirectedExit (ec, label, initializer, set_return_state);
				set_return_state = false;

				if (fin.start_fin_label == null) {
					fin.start_fin_label = ec.DefineLabel ();
				}

				label = fin.start_fin_label.Value;
			}

			return label;
		}

		public static Label EmitRedirectedReturn (EmitContext ec, AsyncInitializer initializer)
		{
			return EmitRedirectedJump (ec, initializer, initializer.BodyEnd, null);
		}

		void EmitRedirectedExit (EmitContext ec, Label label, AsyncInitializer initializer, bool setReturnState)
		{
			if (redirected_jumps == null) {
				redirected_jumps = new List<Label> ();

				// Add fallthrough label
				redirected_jumps.Add (ec.DefineLabel ());

				if (setReturnState)
					initializer.HoistedReturnState = ec.GetTemporaryField (ec.Module.Compiler.BuiltinTypes.Int, true);
			}

			int index = redirected_jumps.IndexOf (label);
			if (index < 0) {
				redirected_jumps.Add (label);
				index = redirected_jumps.Count - 1;
			}

			//
			// Indicates we have captured exit jump
			//
			if (setReturnState) {
				var value = new IntConstant (initializer.HoistedReturnState.Type, index, Location.Null);
				initializer.HoistedReturnState.EmitAssign (ec, value, false, false);
			}
		}

		//
		// Emits state table of jumps outside of try block and reload of return
		// value when try block returns value
		//
		void EmitUnwindFinallyTable (EmitContext ec)
		{
			if (redirected_jumps == null)
				return;

			var initializer = (AsyncInitializer)ec.CurrentAnonymousMethod;
			initializer.HoistedReturnState.EmitLoad (ec);
			ec.Emit (OpCodes.Switch, redirected_jumps.ToArray ());

			// Mark fallthrough label
			ec.MarkLabel (redirected_jumps [0]);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			var da = fc.BranchDefiniteAssignment ();

			var tf = fc.TryFinally;
			fc.TryFinally = this;

			var res_stmt = Statement.FlowAnalysis (fc);

			fc.TryFinally = tf;

			var try_da = fc.DefiniteAssignment;
			fc.DefiniteAssignment = da;

			var res_fin = fini.FlowAnalysis (fc);

			if (try_exit_dat != null) {
				//
				// try block has global exit but we need to run definite assignment check
				// for parameter block out parameter after finally block because it's always
				// executed before exit
				//
				foreach (var try_da_part in try_exit_dat)
					fc.ParametersBlock.CheckControlExit (fc, fc.DefiniteAssignment | try_da_part);

				try_exit_dat = null;
			}

			fc.DefiniteAssignment |= try_da;
			return res_stmt | res_fin;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			//
			// Mark finally block first for any exit statement in try block
			// to know whether the code which follows finally is reachable
			//
			return fini.MarkReachable (rc) | base.MarkReachable (rc);
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			TryFinally target = (TryFinally) t;

			target.stmt = stmt.Clone (clonectx);
			if (fini != null)
				target.fini = (ExplicitBlock) clonectx.LookupBlock (fini);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class TryCatch : ExceptionStatement
	{
		public Block Block;
		List<Catch> clauses;
		readonly bool inside_try_finally;
		List<Catch> catch_sm;

		public TryCatch (Block block, List<Catch> catch_clauses, Location l, bool inside_try_finally)
			: base (l)
		{
			this.Block = block;
			this.clauses = catch_clauses;
			this.inside_try_finally = inside_try_finally;
		}

		public List<Catch> Clauses {
			get {
				return clauses;
			}
		}

		public bool HasClauseWithAwait {
			get {
				return catch_sm != null;
			}
		}

		public bool IsTryCatchFinally {
			get {
				return inside_try_finally;
			}
		}

		public override bool Resolve (BlockContext bc)
		{
			bool ok;

			using (bc.Set (ResolveContext.Options.TryScope)) {

				parent_try_block = bc.CurrentTryBlock;

				if (IsTryCatchFinally) {
					ok = Block.Resolve (bc);
				} else {
					using (bc.Set (ResolveContext.Options.TryWithCatchScope)) {
						bc.CurrentTryBlock = this;
						ok = Block.Resolve (bc);
						bc.CurrentTryBlock = parent_try_block;
					}
				}
			}

			var prev_catch = bc.CurrentTryCatch;
			bc.CurrentTryCatch = this;

			for (int i = 0; i < clauses.Count; ++i) {
				var c = clauses[i];

				ok &= c.Resolve (bc);

				if (c.Block.HasAwait) {
					if (catch_sm == null)
						catch_sm = new List<Catch> ();

					catch_sm.Add (c);
				}

				if (c.Filter != null)
					continue;

				TypeSpec resolved_type = c.CatchType;
				if (resolved_type == null)
					continue;

				for (int ii = 0; ii < clauses.Count; ++ii) {
					if (ii == i)
						continue;

					if (clauses[ii].Filter != null)
						continue;

					if (clauses[ii].IsGeneral) {
						if (resolved_type.BuiltinType != BuiltinTypeSpec.Type.Exception)
							continue;

						if (!bc.Module.DeclaringAssembly.WrapNonExceptionThrows)
							continue;

						if (!bc.Module.PredefinedAttributes.RuntimeCompatibility.IsDefined)
							continue;

						bc.Report.Warning (1058, 1, c.loc,
							"A previous catch clause already catches all exceptions. All non-exceptions thrown will be wrapped in a `System.Runtime.CompilerServices.RuntimeWrappedException'");

						continue;
					}

					if (ii >= i)
						continue;

					var ct = clauses[ii].CatchType;
					if (ct == null)
						continue;

					if (resolved_type == ct || TypeSpec.IsBaseClass (resolved_type, ct, true)) {
						bc.Report.Error (160, c.loc,
							"A previous catch clause already catches all exceptions of this or a super type `{0}'",
							ct.GetSignatureForError ());
						ok = false;
					}
				}
			}

			bc.CurrentTryCatch = prev_catch;

			return base.Resolve (bc) && ok;
		}

		protected sealed override void DoEmit (EmitContext ec)
		{
			if (!inside_try_finally)
				EmitTryBodyPrepare (ec);

			Block.Emit (ec);

			LocalBuilder state_variable = null;
			foreach (Catch c in clauses) {
				c.Emit (ec);

				if (catch_sm != null) {
					if (state_variable == null) {
						//
						// Cannot reuse temp variable because non-catch path assumes the value is 0
						// which may not be true for reused local variable
						//
						state_variable = ec.DeclareLocal (ec.Module.Compiler.BuiltinTypes.Int, false);
					}

					var index = catch_sm.IndexOf (c);
					if (index < 0)
						continue;

					ec.EmitInt (index + 1);
					ec.Emit (OpCodes.Stloc, state_variable);
				}
			}

			if (state_variable == null) {
				if (!inside_try_finally)
					ec.EndExceptionBlock ();
			} else {
				ec.EndExceptionBlock ();

				ec.Emit (OpCodes.Ldloc, state_variable);

				var labels = new Label [catch_sm.Count + 1];
				for (int i = 0; i < labels.Length; ++i) {
					labels [i] = ec.DefineLabel ();
				}

				var end = ec.DefineLabel ();
				ec.Emit (OpCodes.Switch, labels);

				// 0 value is default label
				ec.MarkLabel (labels [0]);
				ec.Emit (OpCodes.Br, end);

				var atv = ec.AsyncThrowVariable;
				Catch c = null;
				for (int i = 0; i < catch_sm.Count; ++i) {
					if (c != null && c.Block.HasReachableClosingBrace)
						ec.Emit (OpCodes.Br, end);

					ec.MarkLabel (labels [i + 1]);
					c = catch_sm [i];
					ec.AsyncThrowVariable = c.Variable;
					c.Block.Emit (ec);
				}
				ec.AsyncThrowVariable = atv;

				ec.MarkLabel (end);
			}
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			var start_fc = fc.BranchDefiniteAssignment ();
			var res = Block.FlowAnalysis (fc);

			DefiniteAssignmentBitSet try_fc = res ? null : fc.DefiniteAssignment;

			foreach (var c in clauses) {
				fc.BranchDefiniteAssignment (start_fc);
				if (!c.FlowAnalysis (fc)) {
					if (try_fc == null)
						try_fc = fc.DefiniteAssignment;
					else
						try_fc &= fc.DefiniteAssignment;

					res = false;
				}
			}

			fc.DefiniteAssignment = try_fc ?? start_fc;
			parent_try_block = null;
			return res;
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			if (rc.IsUnreachable)
				return rc;

			base.MarkReachable (rc);

			var tc_rc = Block.MarkReachable (rc);

			foreach (var c in clauses)
				tc_rc &= c.MarkReachable (rc);

			return tc_rc;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			TryCatch target = (TryCatch) t;

			target.Block = clonectx.LookupBlock (Block);
			if (clauses != null){
				target.clauses = new List<Catch> ();
				foreach (Catch c in clauses)
					target.clauses.Add ((Catch) c.Clone (clonectx));
			}
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	public class Using : TryFinallyBlock
	{
		public class VariableDeclaration : BlockVariable
		{
			Statement dispose_call;

			public VariableDeclaration (FullNamedExpression type, LocalVariable li)
				: base (type, li)
			{
			}

			public VariableDeclaration (LocalVariable li, Location loc)
				: base (li)
			{
				reachable = true;
				this.loc = loc;
			}

			public VariableDeclaration (Expression expr)
				: base (null)
			{
				loc = expr.Location;
				Initializer = expr;
			}

			#region Properties

			public bool IsNested { get; private set; }

			#endregion

			public void EmitDispose (EmitContext ec)
			{
				dispose_call.Emit (ec);
			}

			public override bool Resolve (BlockContext bc)
			{
				if (IsNested)
					return true;

				return base.Resolve (bc, false);
			}

			public Expression ResolveExpression (BlockContext bc)
			{
				var e = Initializer.Resolve (bc);
				if (e == null)
					return null;

				li = LocalVariable.CreateCompilerGenerated (e.Type, bc.CurrentBlock, loc);
				Initializer = ResolveInitializer (bc, Variable, e);
				return e;
			}

			protected override Expression ResolveInitializer (BlockContext bc, LocalVariable li, Expression initializer)
			{
				if (li.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
					initializer = initializer.Resolve (bc);
					if (initializer == null)
						return null;

					// Once there is dynamic used defer conversion to runtime even if we know it will never succeed
					Arguments args = new Arguments (1);
					args.Add (new Argument (initializer));
					initializer = new DynamicConversion (bc.BuiltinTypes.IDisposable, 0, args, initializer.Location).Resolve (bc);
					if (initializer == null)
						return null;

					var var = LocalVariable.CreateCompilerGenerated (initializer.Type, bc.CurrentBlock, loc);
					dispose_call = CreateDisposeCall (bc, var);
					dispose_call.Resolve (bc);

					return base.ResolveInitializer (bc, li, new SimpleAssign (var.CreateReferenceExpression (bc, loc), initializer, loc));
				}

				if (li == Variable) {
					CheckIDiposableConversion (bc, li, initializer);
					dispose_call = CreateDisposeCall (bc, li);
					dispose_call.Resolve (bc);
				}

				return base.ResolveInitializer (bc, li, initializer);
			}

			protected virtual void CheckIDiposableConversion (BlockContext bc, LocalVariable li, Expression initializer)
			{
				var type = li.Type;

				if (type.BuiltinType != BuiltinTypeSpec.Type.IDisposable && !CanConvertToIDisposable (bc, type)) {
					if (type.IsNullableType) {
						// it's handled in CreateDisposeCall
						return;
					}

					if (type != InternalType.ErrorType) {
						bc.Report.SymbolRelatedToPreviousError (type);
						var loc = type_expr == null ? initializer.Location : type_expr.Location;
						bc.Report.Error (1674, loc, "`{0}': type used in a using statement must be implicitly convertible to `System.IDisposable'",
							type.GetSignatureForError ());
					}

					return;
				}
			}

			static bool CanConvertToIDisposable (BlockContext bc, TypeSpec type)
			{
				var target = bc.BuiltinTypes.IDisposable;
				var tp = type as TypeParameterSpec;
				if (tp != null)
					return Convert.ImplicitTypeParameterConversion (null, tp, target) != null;

				return type.ImplementsInterface (target, false);
			}

			protected virtual Statement CreateDisposeCall (BlockContext bc, LocalVariable lv)
			{
				var lvr = lv.CreateReferenceExpression (bc, lv.Location);
				var type = lv.Type;
				var loc = lv.Location;

				var idt = bc.BuiltinTypes.IDisposable;
				var m = bc.Module.PredefinedMembers.IDisposableDispose.Resolve (loc);

				var dispose_mg = MethodGroupExpr.CreatePredefined (m, idt, loc);
				dispose_mg.InstanceExpression = type.IsNullableType ?
					new Cast (new TypeExpression (idt, loc), lvr, loc).Resolve (bc) :
					lvr;

				//
				// Hide it from symbol file via null location
				//
				Statement dispose = new StatementExpression (new Invocation (dispose_mg, null), Location.Null);

				// Add conditional call when disposing possible null variable
				if (!TypeSpec.IsValueType (type) || type.IsNullableType)
					dispose = new If (new Binary (Binary.Operator.Inequality, lvr, new NullLiteral (loc)), dispose, dispose.loc);

				return dispose;
			}

			public void ResolveDeclaratorInitializer (BlockContext bc)
			{
				Initializer = base.ResolveInitializer (bc, Variable, Initializer);
			}

			public Statement RewriteUsingDeclarators (BlockContext bc, Statement stmt)
			{
				for (int i = declarators.Count - 1; i >= 0; --i) {
					var d = declarators [i];
					var vd = new VariableDeclaration (d.Variable, d.Variable.Location);
					vd.Initializer = d.Initializer;
					vd.IsNested = true;
					vd.dispose_call = CreateDisposeCall (bc, d.Variable);
					vd.dispose_call.Resolve (bc);

					stmt = new Using (vd, stmt, d.Variable.Location);
				}

				declarators = null;
				return stmt;
			}	

			public override object Accept (StructuralVisitor visitor)
			{
				return visitor.Visit (this);
			}	
		}

		VariableDeclaration decl;

		public Using (VariableDeclaration decl, Statement stmt, Location loc)
			: base (stmt, loc)
		{
			this.decl = decl;
		}

		public Using (Expression expr, Statement stmt, Location loc)
			: base (stmt, loc)
		{
			this.decl = new VariableDeclaration (expr);
		}

		#region Properties

		public Expression Expr {
			get {
				return decl.Variable == null ? decl.Initializer : null;
			}
		}

		public BlockVariable Variables {
			get {
				return decl;
			}
		}

		#endregion

		public override void Emit (EmitContext ec)
		{
			//
			// Don't emit sequence point it will be set on variable declaration
			//
			DoEmit (ec);
		}

		protected override void EmitTryBodyPrepare (EmitContext ec)
		{
			decl.Emit (ec);
			base.EmitTryBodyPrepare (ec);
		}

		protected override void EmitTryBody (EmitContext ec)
		{
			stmt.Emit (ec);
		}

		public override void EmitFinallyBody (EmitContext ec)
		{
			decl.EmitDispose (ec);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			decl.FlowAnalysis (fc);
			return stmt.FlowAnalysis (fc);
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			decl.MarkReachable (rc);
			return base.MarkReachable (rc);
		}

		public override bool Resolve (BlockContext ec)
		{
			VariableReference vr;
			bool vr_locked = false;

			using (ec.Set (ResolveContext.Options.UsingInitializerScope)) {
				if (decl.Variable == null) {
					vr = decl.ResolveExpression (ec) as VariableReference;
					if (vr != null) {
						vr_locked = vr.IsLockedByStatement;
						vr.IsLockedByStatement = true;
					}
				} else {
					if (decl.IsNested) {
						decl.ResolveDeclaratorInitializer (ec);
					} else {
						if (!decl.Resolve (ec))
							return false;

						if (decl.Declarators != null) {
							stmt = decl.RewriteUsingDeclarators (ec, stmt);
						}
					}

					vr = null;
				}
			}

			var ok = base.Resolve (ec);

			if (vr != null)
				vr.IsLockedByStatement = vr_locked;

			return ok;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Using target = (Using) t;

			target.decl = (VariableDeclaration) decl.Clone (clonectx);
			target.stmt = stmt.Clone (clonectx);
		}

		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	/// <summary>
	///   Implementation of the foreach C# statement
	/// </summary>
	public class Foreach : LoopStatement
	{
		abstract class IteratorStatement : Statement
		{
			protected readonly Foreach for_each;

			protected IteratorStatement (Foreach @foreach)
			{
				this.for_each = @foreach;
				this.loc = @foreach.expr.Location;
			}

			protected override void CloneTo (CloneContext clonectx, Statement target)
			{
				throw new NotImplementedException ();
			}

			public override void Emit (EmitContext ec)
			{
				if (ec.EmitAccurateDebugInfo) {
					ec.Emit (OpCodes.Nop);
				}

				base.Emit (ec);
			}

			protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
			{
				throw new NotImplementedException ();
			}
		}

		sealed class ArrayForeach : IteratorStatement
		{
			TemporaryVariableReference[] lengths;
			Expression [] length_exprs;
			StatementExpression[] counter;
			TemporaryVariableReference[] variables;

			TemporaryVariableReference copy;

			public ArrayForeach (Foreach @foreach, int rank)
				: base (@foreach)
			{
				counter = new StatementExpression[rank];
				variables = new TemporaryVariableReference[rank];
				length_exprs = new Expression [rank];

				//
				// Only use temporary length variables when dealing with
				// multi-dimensional arrays
				//
				if (rank > 1)
					lengths = new TemporaryVariableReference [rank];
			}

			public override bool Resolve (BlockContext ec)
			{
				Block variables_block = for_each.variable.Block;
				copy = TemporaryVariableReference.Create (for_each.expr.Type, variables_block, loc);
				copy.Resolve (ec);

				int rank = length_exprs.Length;
				Arguments list = new Arguments (rank);
				for (int i = 0; i < rank; i++) {
					var v = TemporaryVariableReference.Create (ec.BuiltinTypes.Int, variables_block, loc);
					variables[i] = v;
					counter[i] = new StatementExpression (new UnaryMutator (UnaryMutator.Mode.PostIncrement, v, Location.Null));
					counter[i].Resolve (ec);

					if (rank == 1) {
						length_exprs [i] = new MemberAccess (copy, "Length").Resolve (ec);
					} else {
						lengths[i] = TemporaryVariableReference.Create (ec.BuiltinTypes.Int, variables_block, loc);
						lengths[i].Resolve (ec);

						Arguments args = new Arguments (1);
						args.Add (new Argument (new IntConstant (ec.BuiltinTypes, i, loc)));
						length_exprs [i] = new Invocation (new MemberAccess (copy, "GetLength"), args).Resolve (ec);
					}

					list.Add (new Argument (v));
				}

				var access = new ElementAccess (copy, list, loc).Resolve (ec);
				if (access == null)
					return false;

				TypeSpec var_type;
				if (for_each.type is VarExpr) {
					// Infer implicitly typed local variable from foreach array type
					var_type = access.Type;
				} else {
					var_type = for_each.type.ResolveAsType (ec);

					if (var_type == null)
						return false;

					access = Convert.ExplicitConversion (ec, access, var_type, loc);
					if (access == null)
						return false;
				}

				for_each.variable.Type = var_type;

				var prev_block = ec.CurrentBlock;
				ec.CurrentBlock = variables_block;
				var variable_ref = new LocalVariableReference (for_each.variable, loc).Resolve (ec);
				ec.CurrentBlock = prev_block;

				if (variable_ref == null)
					return false;

				for_each.body.AddScopeStatement (new StatementExpression (new CompilerAssign (variable_ref, access, Location.Null), for_each.type.Location));

				return for_each.body.Resolve (ec);
			}

			protected override void DoEmit (EmitContext ec)
			{
				copy.EmitAssign (ec, for_each.expr);

				int rank = length_exprs.Length;
				Label[] test = new Label [rank];
				Label[] loop = new Label [rank];

				for (int i = 0; i < rank; i++) {
					test [i] = ec.DefineLabel ();
					loop [i] = ec.DefineLabel ();

					if (lengths != null)
						lengths [i].EmitAssign (ec, length_exprs [i]);
				}

				IntConstant zero = new IntConstant (ec.BuiltinTypes, 0, loc);
				for (int i = 0; i < rank; i++) {
					variables [i].EmitAssign (ec, zero);

					ec.Emit (OpCodes.Br, test [i]);
					ec.MarkLabel (loop [i]);
				}

				for_each.body.Emit (ec);

				ec.MarkLabel (ec.LoopBegin);
				ec.Mark (for_each.expr.Location);

				for (int i = rank - 1; i >= 0; i--){
					counter [i].Emit (ec);

					ec.MarkLabel (test [i]);
					variables [i].Emit (ec);

					if (lengths != null)
						lengths [i].Emit (ec);
					else
						length_exprs [i].Emit (ec);

					ec.Emit (OpCodes.Blt, loop [i]);
				}

				ec.MarkLabel (ec.LoopEnd);
			}
		}

		sealed class CollectionForeach : IteratorStatement, OverloadResolver.IErrorHandler
		{
			class RuntimeDispose : Using.VariableDeclaration
			{
				public RuntimeDispose (LocalVariable lv, Location loc)
					: base (lv, loc)
				{
					reachable = true;
				}

				protected override void CheckIDiposableConversion (BlockContext bc, LocalVariable li, Expression initializer)
				{
					// Defered to runtime check
				}

				protected override Statement CreateDisposeCall (BlockContext bc, LocalVariable lv)
				{
					var idt = bc.BuiltinTypes.IDisposable;

					//
					// Fabricates code like
					//
					// if ((temp = vr as IDisposable) != null) temp.Dispose ();
					//

					var dispose_variable = LocalVariable.CreateCompilerGenerated (idt, bc.CurrentBlock, loc);

					var idisaposable_test = new Binary (Binary.Operator.Inequality, new CompilerAssign (
						dispose_variable.CreateReferenceExpression (bc, loc),
						new As (lv.CreateReferenceExpression (bc, loc), new TypeExpression (dispose_variable.Type, loc), loc),
						loc), new NullLiteral (loc));

					var m = bc.Module.PredefinedMembers.IDisposableDispose.Resolve (loc);

					var dispose_mg = MethodGroupExpr.CreatePredefined (m, idt, loc);
					dispose_mg.InstanceExpression = dispose_variable.CreateReferenceExpression (bc, loc);

					Statement dispose = new StatementExpression (new Invocation (dispose_mg, null));
					return new If (idisaposable_test, dispose, loc);
				}
			}

			LocalVariable variable;
			Expression expr;
			Statement statement;
			ExpressionStatement init;
			TemporaryVariableReference enumerator_variable;
			bool ambiguous_getenumerator_name;

			public CollectionForeach (Foreach @foreach, LocalVariable var, Expression expr)
				: base (@foreach)
			{
				this.variable = var;
				this.expr = expr;
			}

			void Error_WrongEnumerator (ResolveContext rc, MethodSpec enumerator)
			{
				rc.Report.SymbolRelatedToPreviousError (enumerator);
				rc.Report.Error (202, loc,
					"foreach statement requires that the return type `{0}' of `{1}' must have a suitable public MoveNext method and public Current property",
						enumerator.ReturnType.GetSignatureForError (), enumerator.GetSignatureForError ());
			}

			MethodGroupExpr ResolveGetEnumerator (ResolveContext rc)
			{
				//
				// Option 1: Try to match by name GetEnumerator first
				//
				var mexpr = Expression.MemberLookup (rc, false, expr.Type,
					"GetEnumerator", 0, Expression.MemberLookupRestrictions.ExactArity, loc);		// TODO: What if CS0229 ?

				var mg = mexpr as MethodGroupExpr;
				if (mg != null) {
					mg.InstanceExpression = expr;
					Arguments args = new Arguments (0);
					mg = mg.OverloadResolve (rc, ref args, this, OverloadResolver.Restrictions.ProbingOnly | OverloadResolver.Restrictions.GetEnumeratorLookup);

					// For ambiguous GetEnumerator name warning CS0278 was reported, but Option 2 could still apply
					if (ambiguous_getenumerator_name)
						mg = null;

					if (mg != null && !mg.BestCandidate.IsStatic && mg.BestCandidate.IsPublic) {
						return mg;
					}
				}

				//
				// Option 2: Try to match using IEnumerable interfaces with preference of generic version
				//
				var t = expr.Type;
				PredefinedMember<MethodSpec> iface_candidate = null;
				var ptypes = rc.Module.PredefinedTypes;
				var gen_ienumerable = ptypes.IEnumerableGeneric;
				if (!gen_ienumerable.Define ())
					gen_ienumerable = null;

				var ifaces = t.Interfaces;
				if (ifaces != null) {
					foreach (var iface in ifaces) {
						if (gen_ienumerable != null && iface.MemberDefinition == gen_ienumerable.TypeSpec.MemberDefinition) {
							if (iface_candidate != null && iface_candidate != rc.Module.PredefinedMembers.IEnumerableGetEnumerator) {
								rc.Report.SymbolRelatedToPreviousError (expr.Type);
								rc.Report.Error (1640, loc,
									"foreach statement cannot operate on variables of type `{0}' because it contains multiple implementation of `{1}'. Try casting to a specific implementation",
									expr.Type.GetSignatureForError (), gen_ienumerable.TypeSpec.GetSignatureForError ());

								return null;
							}

							// TODO: Cache this somehow
							iface_candidate = new PredefinedMember<MethodSpec> (rc.Module, iface,
								MemberFilter.Method ("GetEnumerator", 0, ParametersCompiled.EmptyReadOnlyParameters, null));

							continue;
						}

						if (iface.BuiltinType == BuiltinTypeSpec.Type.IEnumerable && iface_candidate == null) {
							iface_candidate = rc.Module.PredefinedMembers.IEnumerableGetEnumerator;
						}
					}
				}

				if (iface_candidate == null) {
					if (expr.Type != InternalType.ErrorType) {
						rc.Report.Error (1579, loc,
							"foreach statement cannot operate on variables of type `{0}' because it does not contain a definition for `{1}' or is inaccessible",
							expr.Type.GetSignatureForError (), "GetEnumerator");
					}

					return null;
				}

				var method = iface_candidate.Resolve (loc);
				if (method == null)
					return null;

				mg = MethodGroupExpr.CreatePredefined (method, expr.Type, loc);
				mg.InstanceExpression = expr;
				return mg;
			}

			MethodGroupExpr ResolveMoveNext (ResolveContext rc, MethodSpec enumerator)
			{
				var ms = MemberCache.FindMember (enumerator.ReturnType,
					MemberFilter.Method ("MoveNext", 0, ParametersCompiled.EmptyReadOnlyParameters, rc.BuiltinTypes.Bool),
					BindingRestriction.InstanceOnly) as MethodSpec;

				if (ms == null || !ms.IsPublic) {
					Error_WrongEnumerator (rc, enumerator);
					return null;
				}

				return MethodGroupExpr.CreatePredefined (ms, enumerator.ReturnType, expr.Location);
			}

			PropertySpec ResolveCurrent (ResolveContext rc, MethodSpec enumerator)
			{
				var ps = MemberCache.FindMember (enumerator.ReturnType,
					MemberFilter.Property ("Current", null),
					BindingRestriction.InstanceOnly) as PropertySpec;

				if (ps == null || !ps.IsPublic) {
					Error_WrongEnumerator (rc, enumerator);
					return null;
				}

				return ps;
			}

			public override bool Resolve (BlockContext ec)
			{
				bool is_dynamic = expr.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic;

				if (is_dynamic) {
					expr = Convert.ImplicitConversionRequired (ec, expr, ec.BuiltinTypes.IEnumerable, loc);
				} else if (expr.Type.IsNullableType) {
					expr = new Nullable.UnwrapCall (expr).Resolve (ec);
				}

				var get_enumerator_mg = ResolveGetEnumerator (ec);
				if (get_enumerator_mg == null) {
					return false;
				}

				var get_enumerator = get_enumerator_mg.BestCandidate;
				enumerator_variable = TemporaryVariableReference.Create (get_enumerator.ReturnType, variable.Block, loc);
				enumerator_variable.Resolve (ec);

				// Prepare bool MoveNext ()
				var move_next_mg = ResolveMoveNext (ec, get_enumerator);
				if (move_next_mg == null) {
					return false;
				}

				move_next_mg.InstanceExpression = enumerator_variable;

				// Prepare ~T~ Current { get; }
				var current_prop = ResolveCurrent (ec, get_enumerator);
				if (current_prop == null) {
					return false;
				}

				var current_pe = new PropertyExpr (current_prop, loc) { InstanceExpression = enumerator_variable }.Resolve (ec);
				if (current_pe == null)
					return false;

				VarExpr ve = for_each.type as VarExpr;

				if (ve != null) {
					if (is_dynamic) {
						// Source type is dynamic, set element type to dynamic too
						variable.Type = ec.BuiltinTypes.Dynamic;
					} else {
						// Infer implicitly typed local variable from foreach enumerable type
						variable.Type = current_pe.Type;
					}
				} else {
					if (is_dynamic) {
						// Explicit cast of dynamic collection elements has to be done at runtime
						current_pe = EmptyCast.Create (current_pe, ec.BuiltinTypes.Dynamic);
					}

					variable.Type = for_each.type.ResolveAsType (ec);

					if (variable.Type == null)
						return false;

					current_pe = Convert.ExplicitConversion (ec, current_pe, variable.Type, loc);
					if (current_pe == null)
						return false;
				}

				var prev_block = ec.CurrentBlock;
				ec.CurrentBlock = for_each.variable.Block;
				var variable_ref = new LocalVariableReference (variable, loc).Resolve (ec);
				ec.CurrentBlock = prev_block;
				if (variable_ref == null)
					return false;

				for_each.body.AddScopeStatement (new StatementExpression (new CompilerAssign (variable_ref, current_pe, Location.Null), for_each.type.Location));

				var init = new Invocation.Predefined (get_enumerator_mg, null);

				statement = new While (new BooleanExpression (new Invocation (move_next_mg, null)),
					 for_each.body, Location.Null);

				var enum_type = enumerator_variable.Type;

				//
				// Add Dispose method call when enumerator can be IDisposable
				//
				if (!enum_type.ImplementsInterface (ec.BuiltinTypes.IDisposable, false)) {
					if (!enum_type.IsSealed && !TypeSpec.IsValueType (enum_type)) {
						//
						// Runtime Dispose check
						//
						var vd = new RuntimeDispose (enumerator_variable.LocalInfo, Location.Null);
						vd.Initializer = init;
						statement = new Using (vd, statement, Location.Null);
					} else {
						//
						// No Dispose call needed
						//
						this.init = new SimpleAssign (enumerator_variable, init, Location.Null);
						this.init.Resolve (ec);
					}
				} else {
					//
					// Static Dispose check
					//
					var vd = new Using.VariableDeclaration (enumerator_variable.LocalInfo, Location.Null);
					vd.Initializer = init;
					statement = new Using (vd, statement, Location.Null);
				}

				return statement.Resolve (ec);
			}

			protected override void DoEmit (EmitContext ec)
			{
				enumerator_variable.LocalInfo.CreateBuilder (ec);

				if (init != null)
					init.EmitStatement (ec);

				statement.Emit (ec);
			}

			#region IErrorHandler Members

			bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext ec, MemberSpec best, MemberSpec ambiguous)
			{
				ec.Report.SymbolRelatedToPreviousError (best);
				ec.Report.Warning (278, 2, expr.Location,
					"`{0}' contains ambiguous implementation of `{1}' pattern. Method `{2}' is ambiguous with method `{3}'",
					expr.Type.GetSignatureForError (), "enumerable",
					best.GetSignatureForError (), ambiguous.GetSignatureForError ());

				ambiguous_getenumerator_name = true;
				return true;
			}

			bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
			{
				return false;
			}

			bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
			{
				return false;
			}

			bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
			{
				return false;
			}

			#endregion
		}

		Expression type;
		LocalVariable variable;
		Expression expr;
		Block body;

		public Foreach (Expression type, LocalVariable var, Expression expr, Statement stmt, Block body, Location l)
			: base (stmt)
		{
			this.type = type;
			this.variable = var;
			this.expr = expr;
			this.body = body;
			loc = l;
		}

		public Expression Expr {
			get { return expr; }
		}

		public Expression TypeExpression {
			get { return type; }
		}

		public LocalVariable Variable {
			get { return variable; }
		}

		public override Reachability MarkReachable (Reachability rc)
		{
			base.MarkReachable (rc);

			body.MarkReachable (rc);

			return rc;
		}

		public override bool Resolve (BlockContext ec)
		{
			expr = expr.Resolve (ec);
			if (expr == null)
				return false;

			if (expr.IsNull) {
				ec.Report.Error (186, loc, "Use of null is not valid in this context");
				return false;
			}

			body.AddStatement (Statement);

			if (expr.Type.BuiltinType == BuiltinTypeSpec.Type.String) {
				Statement = new ArrayForeach (this, 1);
			} else if (expr.Type is ArrayContainer) {
				Statement = new ArrayForeach (this, ((ArrayContainer) expr.Type).Rank);
			} else {
				if (expr.eclass == ExprClass.MethodGroup || expr is AnonymousMethodExpression) {
					ec.Report.Error (446, expr.Location, "Foreach statement cannot operate on a `{0}'",
						expr.ExprClassName);
					return false;
				}

				Statement = new CollectionForeach (this, variable, expr);
			}

			return base.Resolve (ec);
		}

		protected override void DoEmit (EmitContext ec)
		{
			Label old_begin = ec.LoopBegin, old_end = ec.LoopEnd;
			ec.LoopBegin = ec.DefineLabel ();
			ec.LoopEnd = ec.DefineLabel ();

			if (!(Statement is Block))
				ec.BeginCompilerScope (variable.Block.Explicit.GetDebugSymbolScopeIndex ());

			variable.CreateBuilder (ec);

			Statement.Emit (ec);

			if (!(Statement is Block))
				ec.EndScope ();

			ec.LoopBegin = old_begin;
			ec.LoopEnd = old_end;
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			expr.FlowAnalysis (fc);

			var da = fc.BranchDefiniteAssignment ();
			body.FlowAnalysis (fc);
			fc.DefiniteAssignment = da;
			return false;
		}

		protected override void CloneTo (CloneContext clonectx, Statement t)
		{
			Foreach target = (Foreach) t;

			target.type = type.Clone (clonectx);
			target.expr = expr.Clone (clonectx);
			target.body = (Block) body.Clone (clonectx);
			target.Statement = Statement.Clone (clonectx);
		}
		
		public override object Accept (StructuralVisitor visitor)
		{
			return visitor.Visit (this);
		}
	}

	class SentinelStatement: Statement
	{
		protected override void CloneTo (CloneContext clonectx, Statement target)
		{
		}

		protected override void DoEmit (EmitContext ec)
		{
			var l = ec.DefineLabel ();
			ec.MarkLabel (l);
			ec.Emit (OpCodes.Br_S, l);
		}

		protected override bool DoFlowAnalysis (FlowAnalysisContext fc)
		{
			throw new NotImplementedException ();
		}
	}
}